Triple Conjunction at Sunset Between The Planets Mercury, Jupiter And The Bright Star Regulus

Over the next few nights, observers with low western horizons may be able to observe a triple conjunction between the planets Mercury and Jupiter and the bright star Regulus.

On Friday, August 7, the two planets and star will form an equilateral triangle, 1 degree on a side. Mercury will be on top, Regulus to the left, and Jupiter to the right.

Look for them with binoculars just after sunset. Jupiter will be in the middle and the brightest of the three, at magnitude –1.7. Mercury will be on the right at magnitude –0.7. Regulus will be the faintest of the three, on the left at magnitude +1.3.

Brightness in astronomy is measured on an upside-down scale where the faintest stars visible to the naked eye are magnitude 6, the brightest stars are around magnitude 0, and really bright objects like the sun, moon, and planets have negative magnitudes.

All three of these objects will be very bright, but will be masked by the brightness of the sky just after sunset. If you wait until the sky has darkened, they will probably be too low to observe.

Three nights later, on Monday, August 10, Mercury will have moved away to the left, but Regulus and Jupiter will have moved closer to each other, less than half a degree apart. This conjunction will be very hard to observe because of its low altitude.

This will probably be your last chance to observe Jupiter before it passes behind the Sun on August 26. Look for it in the morning sky in mid-September.

Sky Events For August 2015

Moon Phases

Thursday, August 6, 10:03 p.m. EDT

Last Quarter Moon

The Last Quarter Moon rises around midnight and sets around 3 p.m. It is most easily seen just after sunrise in the southern sky.

Friday, August 14, 10:53 a.m. EDT

New Moon

The Moon is not visible on the date of New Moon because it is too close to the Sun, but can be seen low in the East as a narrow crescent a morning or two before, just before sunrise. It is visible low in the West an evening or two after New Moon.

Saturday, August 22, 3:31 p.m. EDT

First Quarter Moon

The First Quarter Moon rises around noon and sets around midnight. It dominates the evening sky.

Saturday, August 29, 2:35 p.m. EDT

Full Moon

The August Full Moon is known as the Corn Moon, Sturgeon Moon, Red Moon, Green Corn Moon, or Grain Moon. It rises around sunset and sets around sunrise; this is the only night in the month when the Moon is in the sky all night long. The rest of the month, the Moon spends at least some time in the daytime sky.

Observing Highlights

Uranus and the Moon

Wednesday/Thursday, August 5/6, dawn

The Moon will be close to Uranus just before sunrise. In southern South America, the Falkland Islands, and parts of Antarctica, the Moon will actually occult Uranus.

Mercury and Jupiter within 0.6 degrees

Thursday, August 6, dusk

Mercury and Jupiter will pass close to each other, appearing within the same telescope field.

Mercury, Jupiter and Regulus within 1 degree

Friday, August 7, dusk

These three bright objects will form a tight triangular pattern low in the western sky after sunset.

Aldebaran and the Moon

Saturday, August 8, early morning

The waning crescent moon will pass close to the bright red star Aldebaran low in morning twilight. The Moon will occult Aldebaran as seen from the Middle East, eastern Europe, northwestern Asia, Scandinavia, Russia, Alaska, and northwestern Canada.

Jupiter and Regulus within 0.5 degrees

Monday, August 10, dusk

Jupiter will pass just north of the bright star Regulus in the constellation Leo.

Perseid meteor shower peaks

Thursday, August 13, 2 a.m.

The Perseid meteor shower is always the most reliable in the year, and this year benefits from having the moon out of the sky for most of the night. Although Perseid meteors can be seen at any time of night, there are always more meteors after midnight because then the Earth is heading directly into the shower. Although they appear to radiate from a point in the constellation Perseus in the northeastern sky, they can be seen anywhere in the sky.

Mars in the Beehive

Thursday, August 20, before dawn

Mars, just past conjunction with the sun, passes in front of the Beehive Cluster, Messier 44.

Moon close to perigee

Saturday, August 29, 8 p.m. local time

The moon will be closest to the Earth at 11 a.m. on August 30, 222,631 miles or 358,290 km. distant. The moon will be below the horizon at that time for observers in North America. The best time to observe this “supermoon” will be just after it rises on Saturday night, August 29. Those living near the ocean should expect higher tides than normal for the next few days.

Planets

Mercury is visible low in the western sky after sunset for most of the month, This apparition is more favorable for observers in the Southern Hemisphere.

Venus moves from the evening to the morning sky on the 15th, but will be hard to observe for northern observers because of its closeness to the sun. Southern observers will have an easier time, and on the 15th may actually be able to observe Venus as a morning star in the east and an evening star in the west.

Mars reappears in dawn twilight after its conjunction with the sun on June 14.

Jupiter is too close to the sun to observe this month.

Saturn is well placed in Libra in the evening sky.

Uranus rises in the late evening in Pisces. 

Neptune rises in the mid-evening in the constellation Aquarius.


Find The Brightest And Nearest Of The Dwarf Planets

With all the news this past week about Pluto, most skywatchers aren’t aware that Ceres, the brightest and nearest of the dwarf planets, will be coming into opposition to the sun on Saturday morning, July 25.

An object is said to be in opposition when it is directly opposite the sun in Earth’s sky. When an object is in opposition, it rises at sunset, is visible all night, and then sets at sunrise.

When Ceres was discovered by Giuseppe Piazzi on the first day of the 19th century, January 1, 1801, it was initially thought to be a planet. Other objects were soon discovered in the gap between the orbits of Mars and Jupiter, so a new name was proposed for these tiny bodies, “asteroids.” This was because of their resemblance to stars in the telescopes of the day.

When the International Astronomical Union proposed a new category, “dwarf planet,” in 2006, Ceres was included, along with Pluto, Eris, Haumea, and Makemake. So tiny Ceres has been called three different things in the 214 years since it was discovered: planet, asteroid, and now dwarf planet.

Despite its recent designation as a dwarf planet, Ceres is still considered to be an asteroid by most astronomers. As such, it is the largest of the asteroids at 592 miles (952 km) in diameter, almost twice the diameter and four times the mass of the next largest asteroids, Pallas and Vesta. On the other hand, it is far smaller than any of the other designated dwarf planets. It is also smaller than fifteen of the moons in the solar system, including Earth’s moon.

This year, Ceres reaches opposition just on the Sagittarius side of the border between Sagittarius and the little-known constellation Microscopium. It is most easily found by looking within the triangle formed three 4th magnitude stars: 62 Sagittarii, the easternmost star in Sagittarius, Omega Capricorni, the southernmost star in Capricornus, and Gamma Microscopii, the brightest star in the dim constellation Microscopium, the Microscope.

On Saturday morning, July 25, the dwarf planet Ceres will be in opposition to the sun on the border between Sagittarius and Microscopium. Credit: Starry Night software.

Because of its faintness, magnitude 7.5 at opposition, detailed charts are needed to distinguish Ceres from the stars it’s passing in front of. Our chart shows its position on the morning of opposition, Saturday, July 25. If you try to find it on any other night, you will need to plot its position with a program like Starry Night or SkySafari.

A detailed chart for locating 7th magnitude Ceres on July 25. Credit: Starry Night software.

As seen in even the largest telescopes on Earth, Ceres appears as a point of light, no different than the background stars. The only way to be sure you have seen it is to plot its position and then try to observe the same area on another night.

On March 6 this year, the Dawn spacecraft entered orbit around Ceres, and has since been returning detailed images of Ceres’ surface. Thus, 2015 marks a special year for the exploration of the solar system, with Dawn orbiting Ceres and New Horizons flying close to Pluto.

Catch The Double Crescents This Week: Venus and the Moon

On Saturday evening, July 18, the crescent moon, moving eastward in the sky, will pass directly below the crescent planet Venus, moving westward, soon to pass below the sun.

On Saturday, July 18, the moon passes just below the planet Venus, both objects showing narrow crescents.  Credit: Starry Night software.

Both objects are being back-lit by the Sun, so that both appear in our sky as crescents. The moon is just three days past new moon, so only nine percent of its disk is lit by the sun. The remaining 91 percent is lit by sunlight reflecting off the surface of the Earth, what is called “earthshine” or “earthlight.” Sometimes this view is also called “the old moon in the new moon’s arms.”

To the naked eye, Venus appears like a brilliant pinpoint of light. Turn your binoculars on it, and that slight additional magnification will allow you to see that Venus is also a narrow crescent.

Because Venus is farther away than the moon, it is lit by the sun at a slightly different angle, so is nineteen percent illuminated, a slightly fatter crescent than the moon.

Some observers have suspected a faint glow coming from the part of Venus not in direct sunlight, a phenomenon called “the ashen light.” No one knows exactly what causes this glow, but it has been reported by many experienced astronomers. Spectroscopic observations have shown pulses in the light, so it might be due to lightning in the hot acidic atmosphere of Venus.

As mentioned above, even small binoculars provide enough magnification to turn the naked-eye pinpoint of Venus into a visible crescent. This is one of many objects in the sky which are revealed or enhanced in binoculars, which is why they are considered an essential tool for all serious skywatchers.

Binoculars for astronomy should have a front aperture of at least 50 millimeters (2 inches). This is seven times the diameter of the fully dark-adapted eye. Such a small binocular has seven times the resolution and 50 times the light-gathering power of the naked eye. 50 millimetre binoculars come in two magnifications, 7 power (7x50) and 10 power (10x50). Both are very useful for astronomy, but I prefer the 10x50 because of its slightly higher magnification and better contrast in a bright sky. I find more powerful binoculars too heavy to hold steadily for any length of time, and mounting them on a tripod defeats the ease of use.

Venus and Jupiter, Up Close and Personal

If you’ve been watching the western sky just after sunset lately, you will have noticed two bright objects, gradually drawing closer.

These are the two brightest planets, Venus and Jupiter. Venus is the brighter of the two, currently magnitude –4.6 on the upside-down brightness scale astronomers use. It will get slightly brighter over the next 10 days, reaching greatest brilliancy on July 10 at magnitude –4.7.

Jupiter is somewhat fainter at magnitude –1.8, down from a maximum of –2.6 when it was in opposition on February 6.

Although the two planets look very close in Earth’s sky, they are in fact very far apart, on opposite sides of the sun. The first graphic shows their true positions, as seen from far above the sun’s north pole. Venus is slightly nearer Earth than the sun, 0.512 astronomical units distant (47.6 million miles or 76.5 million km.) while Jupiter is 6.083 astronomical units away (565 million miles or 910 million km.) on the far side of the sun.

Seen from far above the sun’s north pole on Wednesday, July 1, Earth, Venus and Jupiter lie almost on a perfect straight line.  Credit: Starry Night software.

Viewed in a telescope, the two planets are, by coincidence, exactly the same apparent size, 32 arc seconds in diameter, about a 60th of the apparent diameter of the moon, but look very different.

Seen in the eyepiece of a telescope magnifying 65 times at sunset on July 1, Venus and Jupiter appear very close, but look very different, even though both are the same angular size. Credit: Starry Night software.

Venus, with its bright cloud cover and closeness to the sun, is a brilliant white crescent, lit from slightly behind because it is moving between us and the sun. Jupiter’s cloud tops are somewhat darker than Venus’, but it is also more than seven times farther away from the sun. As a result, despite its large size, Jupiter appears much fainter in a telescope than Venus.

Two bright planets in close proximity make a striking sight with the naked eye. In binoculars you should be able to see that Venus is a tiny crescent and Jupiter is a disk accompanied by 3 tiny moons (on July 1, Callisto will be behind Jupiter). A small telescope will make the view much clearer.

As you continue to watch these two planets over the next few weeks you will see them draw apart as both get closer to the sun, Venus passing between us and the sun on August 15, and Jupiter passing behind the sun on August 26. In another month, both will reappear in the morning sky, where they will join Mars, which passed behind the sun on June 14.

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Spot Mercury At Dawn

Mercury is always a difficult object to spot, always clinging closely to the sun’s apron strings. But you might be excused for missing its brief appearance this week in the dawn skies.

After many attempts to observe Mercury, I’ve found that the best time to spot it is about half an hour before sunrise in the morning sky, or half an hour after sunset in the evening sky. It’s always a balancing act between Mercury’s low altitude and the brightness of the background sky. I find 7x50 or 10x50 binoculars helpful in spotting Mercury, though once I’ve located Mercury in binoculars I usually have no trouble seeing it naked eye.

Unless you’re paying close attention to the sky, you’re likely to miss the current apparition of Mercury. In the northern hemisphere, Mercury can be seen half an hour before sunrise. Credit: Starry Night Software.

Because of the tilt of the ecliptic, the path the Sun and planets follow across the sky, some apparitions of Mercury are more favorable than others. Usually apparitions which are favorable for observers in the northern hemisphere are unfavorable for observers in the southern hemisphere, and vice versa.

The tilt of the ecliptic would indicate that this apparition favors southern observers, but as you can see from these two views, it really isn’t much different: catching Mercury this week will be a challenge for observers everywhere in the world.

A secondary factor affecting Mercury’s visibility is the tilt and eccentricity of its orbit. At 7 degrees, Mercury’s tilt is greater than any other planet. The eccentricity of its orbit, which measures how far it deviates from a circle, is also the greatest, more than twice as eccentric as Mars’ orbit.

The tilt this week also favors southern observers, as you can see in the charts, where Mercury’s orbit is marked in red and the ecliptic in green, but even this doesn’t help much.

The view is not much better in the southern hemisphere. Credit: Starry Night software.

If you are successful in spotting Mercury in the next few days, congratulate yourself, and let us know here!

SkyWatching: Stars Of Early Summer

Early summer is an “in-between” time in the skies. The realm of the galaxies has moved off to the west, but the summer Milky Way has not yet arrived. This is the best time of year to observe globular clusters and double stars.

The centrepiece of the early summer constellations is Boötes, the herdsman, with the bright star Arcturus at his heart. Arcturus is easy to find by following the “arc” of the Big Dipper’s handle away from the ladle: it is the only bright star in this part of the sky. Alternately, if you live in the northern hemisphere, simply look straight overhead around 11 p.m.

Just after dark on a June evening, look overhead to see the constellations of early summer: Boötes, Corona Borealis, and Serpens Caput.  Credit: Starry Night software.

Although Boötes looks like it might be pronounced like “booties,” the diaeresis (double dot) over the second “o” gives you a clue: the two “o”s are pronounced separately: Boh-OO-tes. Its stars form a distinctive kite shape, complete with tail.

Arcturus is the third brightest star in the night sky, after Sirius and Canopus. It is relatively close to us, only 37 light years distant. It is an orange giant star, slightly cooler than the sun, but quite a bit larger in diameter.

Boötes contains relatively few deep sky objects, but is rich in double and variable stars. Izar (Epsilon Boötis) is one of the finest double stars in the sky. With a separation of only 2.9 arc seconds, it requires at least 3 inches aperture, steady skies, and high magnification to see its duality; its stars are gold and greenish in colour. Alkalurops (Mu Boötis) is a much wider double at 2 arc minutes separation, but it is a challenge to see that one of its stars is itself a double.

Although not within Boötes itself, most amateur astronomers use the stars of Boötes to starhop to the Messier globular cluster Messier 3 in the dim constellation of Canes Venatici. M3 forms an almost perfect equilateral triangle with Arcturus and Rho Boötis. This is one of the finest globular clusters in the sky.

Just to the left (east) of Boötes is a small circlet of stars forming Corona Borealis, the northern crown. Look within the circle to see if you can see R Corona Borealis, a very unusual variable star. Some have called this an “inverse nova.” Most of the time it shines steadily with a brightness of about magnitude 7, just below naked eye visibility, but easily seen in binoculars. At long and irregular intervals, instead of brightening like a nova, it dims by about 6 magnitudes. This dimming is caused by occasional expulsion of a dark obscuring cloud of dust. Currently R is entering its dark phase, but keep watching, and it should soon reappear.

These three constellations contain many interesting objects to look at with binoculars or a small telescope. Credit: Starry Night software.

Below Corona Borealis is one of the most unusual constellations, or rather “half constellations.” Serpens represents a snake cut in half, each half held in one hand of Ophiuchus. This is the front half: Serpens Caput, or the head of the serpent. The other half, located quite a ways to the east, is Serpens Cauda, the tail of the Serpent. A triangle is supposed to represent the head of the spent, but I always see this and the two stars above as a large “X.”

The brightest star in Serpens bears the ugly name Unukalhai, which is Arabic for “the serpent’s neck.” Just above Unukalhai is Delta Serpentis, a fine pair of pale yellow stars in a telescope.

But the real prize in Serpens Caput is the globular cluster Messier 5, every bit as fine as Messier 3 to the northwest. Like all globular clusters, M5 responds well to aperture and magnification. Besides resolving the cluster into myriads of tiny stars, a large telescope will reveal chains of stars and clusters within the cluster.

Twenty Great Fuzzies: Brilliant Treasures Lie Buried Within The Constellations

Introduction

Brilliant treasures lie buried within the constellations. Collected here for your delight: twenty "objects"; favorites of many amateur astronomers. Among these twenty "fuzzy" targets are star clusters, nebulae, and galaxies. They make  a rewarding starting point for the exploration of the deep sky.

Of course, comets are fuzzies too. Fuzzy, but fickle. Sometimes their orbits (and therefore their return dates) are known. Sometimes not. And you never know in advance just how good—or how disappointing—the cometary show will be. So here, we've chosen to profile only those objects that will always be there for you.

Most are visible to the naked eye or with binoculars under a clear, moonless night. This list is just a hint of what's out there. Celestial riches abound, hidden out there among—and beyond—the stars.

The Eta Carinae Nebula

Eta Carinae (pronounced "ATE-ah ca-RYE-nee") is the largest and most splendid diffuse nebula in the sky, surpassing even the famous Orion Nebula (M42) in size and glory. Only its position far south of the celestial equator prevents this nebula from being a household name. You can't see it from much of the Northern Hemisphere.

Eta Carinae is a colossal star-forming region of hot gas, heated by ultraviolet rays from its hot young stars. It covers a full two degrees of sky (four times the width of the full moon).

Eta Carinae is obvious to the naked eye as a bright, elongated glow, but that only hints at its telescopic grandeur. With binoculars it appears large and bright. Its nebulosity seems split in two by a V-shaped dark lane of dust, called the Keyhole Nebula.

The field of view in most binoculars is just stunning, with Eta Carinae embedded in the star-studded Milky Way. A telescope will reveal many bright wisps, dark lanes, and subtle details that will keep the most ardent observer busy for years. And don't neglect the two open clusters—NGC 3532 and NGC 3114—that flank the Eta Carinae Nebula. 

The star at the center of the nebula has a unique story to tell. Eta Carinae is one of the most massive stars known, 100 times the mass of our sun. It emits four million times as much light as our friendly local star, making it the brightest object in the sky when viewed through an infrared detector. Eta Carinae is a highly unstable star which fluctuates greatly in brightness. It will undoubtedly explode as a supernova soon.

On the cosmic time scale, "soon" means anytime in the next few hundred thousand years. But it could happen in your lifetime. It could happen tonight! Today the star is at the edge of naked eye visibility, but an outburst in the mid-18th century temporarily made Eta Carinae the second brightest star in the night sky, trailing only Sirius—and not by very much! This outburst ejected gas that now surrounds the central star and is known as the Homunculus Nebula, itself a great "fuzzy" for southern sky watchers with telescopes.

The Great Orion Nebula

The Great Orion Nebula (M42) is visible to the naked eye as a fuzzy patch in the middle of Orion's sword. It's called the "great" one because there are other nebulae in Orion.

What astronomers call the Orion Nebula is just the central part of a larger cloud that stretches across several hundred light years. Four bright stars in a parallogram near the nebula's center form the so-called Trapezium. They're the spotlights that let us see this celestial show. These hot young stars heat up the surrounding gas clouds, causing the nebula to emit light.

The Orion Nebula is full of hot, bright blue stars. It's an area of active star formation. The Hubble Space Telescope has found protoplanetary disks of gas and dust around some of these stars. These disks are about twice the size of our solar system, and may eventually condense to form exoplanets or binary stars. 

M42 is a veritable catalog of different object types, including multiple stars, reflection nebulae, and emission nebulae. Try to view the Great Orion Nebula whenever you can, with whatever you've got: telescope, binoculars, or your eyes. The wealth of detail visible in this nebula is outstanding. The intricate wisps, shapes, and the contrast between brighter and darker regions will never cease to amaze you.

The Andromeda Galaxy

The Andromeda Galaxy is one of the most magnificent objects in the night sky and undoubtedly the most famous galaxy outside our own Milky Way.

Persistent staring with your naked eyes will reveal it as a surprisingly large hazy patch. Andromeda covers as much of the sky as five full moons put together!

Binoculars will show Andromeda in its entirety along with two of Andromeda's companion galaxies, M32 and M110. Careful observation of the nuclear region with a telescope will reveal faint dust lanes.

M31 was once thought to be a nebula inside our galaxy, but in 1923, astronomer Edwin Hubble showed that it was outside the Milky Way.

And it wasn't the only one! Andromeda opened our eyes to the true scale of the cosmos. M31 is now about 2.9 million light-years away. It is over 150,000 light-years across and has a mass 1.2 trillion times that of our sun.

And it's headed this way! Andromeda will collide with our own galaxy, perhaps five billion years from now. It's larger than the Milky Way too, and will devour us. Or, at least, merge with us.

Andromeda's done that before. The Hubble Space Telescope has shown that the Andromeda Galaxy has a double nucleus, indicating that it probably cannibalized another large galaxy.

Omega Centauri

Omega Centauri is the finest globular cluster in the night sky. First discovered by Edmond Halley (better known for predicting the return of the comet that still bears his name) in 1677, Omega Centauri is a blazing ball containing over one million stars in an area larger than the full moon. Even the Hercules Cluster (M13) pales in comparison to Omega Centauri.

Omega Centauri is visible to the naked eye, but is truly delightful with binoculars. Step up to a telescope and you'll be simply amazed at the number of bright stars you can resolve. Use low magnification to see the cluster in its entirety and then zoom in for a closer look. 

Omega Centauri's bulk is equal to five-million solar masses. That's ten times the mass of most globular clusters, and as much as some small galaxies.

The stars in Omega Centauri did not all form at the same time, indicating that it may be the nuclear remnant of a small galaxy that merged with the Milky Way sometime in the distant past.

The Great Hercules Cluster

The Great Hercules Cluster (M13) is one of the sky's most precious jewels and among the best globular clusters in the Northern Hemisphere. Visible to the naked eye under dark skies, M13 looks like a fuzzy ball of light in binoculars. A moderate-sized telescope and high magnification shows a blazing ball of stars with many individual members resolved.

The Great Hercules Cluster contains about 400,000 stars, spread across 140 light-years of space. The star density near the cluster's center is extremely high, with stars separated by only a few astronomical units.

M13 was originally discovered by Edmond Halley. Because it compacts a lot of stars in a small area, M13 was selected as a target for one of the first radio messages broadcast to extraterrestrials from the Arecibo Observatory in Puerto Rico. But don't stay on hold waiting for them to pick up the call. If alien civilizations exist in the Great Hercules Cluster, we won't receive their reply for at least 50,000 years; M13 is 25,000 light-years from Earth.

The Large Magellanic Cloud

The Large Magellanic Cloud (LMC) is one of the closest galaxies to our own Milky Way. It's only 180,000 light years away, and closer than its companion galaxy, the Small Magellanic Cloud. 

But don't expect the LMC to have that classic spiral galaxy shape. Because of the gravitational attraction of the Milky Way—which is ten times larger—the Large Magellanic Cloud has an irregular shape and no central core. 

The LMC spans several degrees in the southern sky and can be easily seen with the unaided eye by observers south of the equator. But it was unknown to Europeans until the voyage of Portuguese explorer Ferdinand Magellan in 1519.

It appears as a huge and diffuse cloud in the sky and contains a treasure trove of celestial objects. Amongst its many interesting sights are nebulae, globular and open clusters, planetary nebulae, dust clouds, and a giant region of hydrogen gas. 

In 1987, supernova 1987A exploded in the LMC, the nearest supernova in 400 years. The most prominent object in the LMC is the Tarantula Nebula, a large diffuse nebula. Sweep through this region with binoculars and rich field—or wide angle—telescopes to take it all in. But don't forget to zoom in afterwards and take some closer looks.

The Pleiades

The Pleiades is the most famous of all open star clusters, containing around 500 members set against a black velvet sky. This young first magnitude open cluster is easily visible to the unaided eye and resembles a smaller version of the Big Dipper. At least six hot blue stars are readily visible and keen-eyed observers can see more.

It's a large diameter object; fully two degrees or four full moon-widths. So M45 is best seen with binoculars. A faint veil of nebulosity surrounds the brightest Pleiades members, with the most easily observable patch being the Merope Nebula (IC 349), which surrounds the star Merope. These reflection nebulae are not remnants of the gas cloud where the Pleiades was born, but a chance cloud of dust that the cluster is passing through. 

In some ancient cultures, ceremonies to honor the dead were held on the day when the Pleiades reached its highest point in the sky at midnight (this is around Halloween). Ancient Aztecs believed the Pleiades would be overhead at midnight the day the world ended.

NGC 6231

NGC 6231 is one of the prettiest premium open clusters in the sky. It shines at magnitude 2.6 and spans an area half that of the moon.

It's easy to mistake it for a comet. You can imagine the stars Zeta 1 Scorpii and Zeta 2 Scorpii forming the comet's nucleus and NGC 6231, Collinder 316, and Trumpler 24 to the north forming the tail. 

This very young open cluster (about three million years old) contains lots of young hot giants and supergiants. It also contains two extremely rare Wolf-Rayet stars, which are very hot, massive stars rapidly bubbling off their bulk and converting it to super-hurricane-force stellar winds.

The Double Cluster

The famous Double Cluster in Perseus is one the night sky's finest jewels. NGC 869 and 884 are a pair of bright and large open clusters embedded in the faint glow of the Milky Way. 

This double cluster is visible without optical aid, but binoculars are required to separate the two clusters, which are half a degree apart. A rich-field telescope gives the best view of the Double Cluster, with many stars of differing brightness visible. 

NGC 869 is more tightly packed than NGC 884. Both clusters are about 7,000 light-years away and are part of the Perseus arm, one of the spiral arms of our Milky Way. The two clusters are actually a few hundred light-years apart.

The Small Magellanic Cloud

The Small Magellanic Cloud (SMC) is an irregular galaxy orbiting the Milky Way. Your eye will see it as a hazy patch of light in the sky about three degrees across. But you have to be pretty far south in the Northern Hemisphere or south of the equator to see it. 

Because of its low surface brightness, it might not be visible in the light-polluted skies of cities. It is best viewed with binoculars and telescopes under low magnification. 

Portuguese explorer Ferdinand Magellan was the first European to note the galaxy, during his attempted circumnavigation of the globe in 1519. Magellan promptly adopted the SMC as a navigational aid. 

The SMC is 200,000 light-years away, slightly more distant than its neighbor, the Large Magellanic Cloud. It is a small galaxy, with an estimated mass of two billion suns. Gravitational interactions with the Large Magellanic Cloud and the Milky Way have distorted its shape.

The Ring Nebula

M57 is called the Ring Nebula and it's obvious why. Astronomers estimate that the shell of this planetary nebulawas blown off about 20,000 years ago.

The different colors of the shell visible in photographs represent different elements. Helium gas emits blue light, oxygen emits green light, and carbon emits red light. The apparently empty region between the shell and the central star is actually filled with gas. This area only appears as a void because it is so hot that the gas emits most of its energy as ultraviolet rays instead of visible light.

M57 is tiny but bright when viewed from the Earth. Because its brightness is spread over a small area, it is best viewed under high magnification. The 14th magnitude central star (a white dwarf) is difficult to identify without a fairly big telescope.

The Bode’s and Cigar Galaxies

M81 and M82 are perhaps the most famous pair of galaxies in the sky. Both can be seen in the same low magnification field of view and both are spiral galaxies. However, M81 is viewed nearly face-on, while M82 is edge-on.

M81 is one of the brightest galaxies in the Messier catalog and can be seen with most binoculars. Long exposure photographs display two prominent spiral arms, which may also be observed with larger telescopes. M81 and M82 are separated by only 150,000 light-years.

This could have been the scene of a colossal cosmic collision. It's astounding to realize that what you're actually seeing is the result of a very near miss. Tens of millions of years ago, the larger (and ten times as massive) M81 passed close by its smaller neighbor. As a result of the rising star tides during that encounter, M82 now glows with the fireworks of starburst formation.

The Whirlpool Galaxy

The Whirlpool Galaxy might just be the most impressive galaxy for amateur astronomers. It is easy to locate with binoculars and it lies just over three degrees northwest of Alkaid, the star at the end of the Big Dipper's handle.

The Whirlpool is a face-on galaxy, making its spiral structure easy to observe. A telescope, dark skies, and moderate power will begin to reveal the spiral arms.

M51 has a bright central core but no stars can be resolved. The core likely contains a supermassive black hole. Of special interest is the bridge of nebulosity that connects M51 to its companion galaxy, NGC 5195. The gravitational pull of NGC 5195 is touching off a volley of new star-formation in the Whirlpool Galaxy.

The Lagoon Nebula

The Lagoon Nebula (M8) is a magnificent object easily seen by the naked eye as a large hazy patch in the sky. The Lagoon is a bright emission nebula with an embedded open cluster. The cluster of young stars is heating the nebula's gas and causing it to emit light.

With binoculars you'll see the dark lane that divides the nebula's brighter regions and gives this object its name. A small telescope begins to reveal this nebula's intricate folds and dark regions amidst brighter areas.

Dark Bok globules in the nebula mark dense clouds of gas and dust. These are sites of star birth. The Trifid Nebula lies close to M8 and both nebulae can be seen in the same binocular field of view.

The Beehive Cluster

The Beehive Cluster was first described by Galileo, but it has been known as long as humans have watched the skies. It is easily visible to the unaided eye as a faint round patch of luminosity. Your binoculars will reveal a cosmic swarm of bees, buzzing with gravitational energy. Many of these stars are close enough to attract each other and the cluster contains many double stars.

The Beehive occupies 1.2 degrees of sky and is set against a region of low star density, making it stand out even more. The cluster contains several hundred stars and may share a common origin with the Hyades Cluster.

The Crab Nebula

The Crab Nebula is the remnant of a star that exploded as a supernova in 1054 A.D. The supernova was visible in the daytime for 23 days, shining four-times brighter than Venus. The supernova was visible to the naked eye in the night sky for almost two years before fading out. What we see today is the gaseous material ejected by the exploding star. This material is moving outward from the nebula's center at 1,800 kilometers (1,080 miles) per second. At the nebula's core is an extremely dense neutron star or pulsar, which rotates 30 times per second. 

Astronomer Charles Messier observed the Crab Nebula in 1758 while searching for Comet Halley. This was the inspiration for Messier to develop a list of all celestial objects that might be mistaken for comets—the Messier catalog. The Crab Nebula is the only supernova remnant in the Messier catalog. 

The Crab Nebula can be a disappointing object for stargazers. Look for a dim, elongated glow in a small telescope or good binoculars. A network of fine filaments can be glimpsed with a large telescope under dark skies and averted vision. Discern the classic "S" shape of the nebula's central region. The central pulsar is, of course, tiny and is not visible.

The Rosette Nebula

The Rosette Nebula is a vast cloud of dust and gas spanning more than the width of two full moons. Open cluster NGC 2244 formed inside the Rosette Nebula. The hottest young stars in NGC 2244 excite the surrounding gas clouds, causing the nebula to emit light.

The Rosette Nebula is about 130 light-years in diameter and 5,500 light-years distant.

A Galactic Glutton

A huge jet of hot ionized gas (plasma) extends out from the nucleus, but it is only visible through the largest amateur telescopes. Despite its huge size, M87 resembles an unresolved globular cluster. It's like a titanic puffball and offers little in the way of details in small telescopes. A tiny 11th magnitude elliptical galaxy, NGC 4478 can be observed close to M87.

The Eagle Nebula

The Eagle Nebula is the subject of the most famous Hubble Space Telescope photo, the "pillars of creation" image that shows columns of cool hydrogen gas and dust protruding from a molecular cloud. New stars are being formed within these clouds. 

A young, hot cluster of stars lights up this emission nebula in the Sagittarius spiral arm of the Milky Way, which is a treasure trove for amateur astronomers. Many nights can be spent with the naked eye and binoculars scanning this area.

The "Big Chicken," as it's sometimes called among amateur astronomers, is visible as a hazy patch under dark skies with the unaided eye. The view through binoculars can be breathtaking with M16, M17, M18, and M24 framed in the same field of view against the background glow of the Milky Way.

M16 itself is an open cluster surrounded by a haze of nebulosity. Although not as spectacular as in photographs, this is nonetheless a tantalizing object best seen with binoculars and with low power in telescopes.

The Triangulum Galaxy

A possible satellite of the Andromeda Galaxy, the Triangulum Galaxy is quite small, with a mass one-seventh that of the Milky Way.

In a truly dark and transparent sky, one may be able to get a glimpse of this galaxy, making it one of the most distant objects visible to the naked eye, at 2.9 million light-years.

Binoculars show that M33 has an oval glow while a telescope will begin to reveal subtle details.

Keep Digging!

These twenty great fuzzy targets are just the barest beginning!

Congratulations, you're now an astronomically wealthy individual!

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app for iOS and Android.  It is available for mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto. 

Spot The Asteroid Pallas In The Sky

Most of us have played video games shooting at asteroids, or watched a starship maneuvering through the Asteroid Belt on television. But have you ever seen a real asteroid in the sky? This week is an excellent opportunity to see one of the largest asteroids, Pallas, as it reaches opposition to the Sun.

The first asteroids were discovered in the early years of the 19th century. The first four asteroids, including Pallas, were discovered in a 6 year period from 1801 to 1807; a fifth asteroid was not discovered until 38 years later in 1845. This ushered in a rich period of asteroid discovery, with three dozen more discoveries in the next decade. Once photography came into play, thousands more asteroids were found.

Astronomers originally thought the first asteroids were very small planets, but once they realized how numerous they were, they created a special category called “asteroids” (because of their resemblance to stars) or “minor planets.” The vast majority of these asteroids have orbits between the orbits of Mars and Jupiter, a region of the Solar System that came to be known as the “Asteroid Belt.”

The Asteroid Belt in reality is quite different from what you see in science fiction programs. Rather than being crowded with space rocks, the Asteroid Belt is mostly empty space. Most of the time, if you were standing on one asteroid, you would need binoculars or a telescope to spot the nearest asteroid. The chances of two asteroids colliding is virtually zero.

The first asteroid discovered, Ceres, has now been reclassified as a dwarf planet, along with Pluto and Eris. At 592 miles (952 kilometres) in diameter, it is significantly larger than the remaining asteroids. Two asteroids, Pallas and Vesta, are almost identical in size, 326 miles (524 km) and 318 miles (512 km) respectively. The rest range from Hygiea (276 miles/444 km) on down through chunks of rock only 30 feet (10 meters) across. Anything smaller than that is called a “meteoroid.”

Although Pallas and Vesta are nearly identical in size, they are quite different in their composition and appearance. Pallas is a typical rocky asteroid, quite dark in surface colour, resembling a carbonaceous chondrite meteorite. Vesta, on the other hand, is highly reflective, the only asteroid sometimes visible with the naked eye.

For the rest, binoculars are needed to spot them. Asteroids, as their name implies, look exactly like faint stars. What gives them away is their rather rapid movement against the background stars.

This week Pallas reach opposition in the eastern part of Hercules, very close to the 4th magnitude star Lambda Herculis. It is motoring along from east to west at about one degree per week, so that in three weeks time it will be close to the 3rd magnitude star Sarin (Delta Herculis). Its movement from night to night, as seen in binoculars, is quite obvious.

The large asteroid Pallas will be in opposition to the Sun in Hercules on Thursday, June 11.  Credit: Starry Night software.

The path of Pallas over the next 14 days carries it parallel to the stars Lambda Hercules and Sarin. The labeled dot is Pallas’ position on June 11, and the dots to the right mark its daily travel westward. Credit: Starry Night software.

I particularly like watching asteroids when they are passing close to a bright star. In a telescope, you can see their movement over even a 15-minute period.

At opposition, Pallas will reach magnitude 9.4, making it easily visible in binoculars. It will be 2.405 astronomical units from Earth, or 224 million miles (360 million km). A tiny object, sure enough, but interesting to see with your own eyes.

Venus At Its Brightest

If you’ve been watching the sky in the early evening lately, you can’t have missed seeing the planet Venus in the west.

Credit: Starry Night software.

Venus has been travelling around its orbit towards us, appearing in evening twilight higher and higher in the sky. This week on Saturday, June 6, it reaches its greatest angular distance from the sun, 45 degrees, at what is called “greatest elongation east.” Even though we are looking at it in the western sky, it is elongated in the direction of the eastern horizon, so it is east of the sun in astronomical terminology.

As seen in a small telescope, Venus this week appears like a brilliant miniature first quarter moon. However, unlike the moon’s pock-marked surface, Venus appears perfectly smooth. That’s because we are seeing only the tops of its dense clouds, which mostly appear a featureless blank white.

Beneath those bland clouds lies one of the most bizarre of alien worlds: the greenhouse effect gone wild with a terrain of bare rock heated to a uniform world-wide temperature of  864 degrees Fahrenheit (462 degrees Celsius), where the endless clouds rain down sulfuric acid.

There are, in fact, vague shadings in the surface of Venus’ clouds. These are best seen with a deep violet filter such as the Wratten 47 available in most telescope stores. It also helps to observe Venus in a daylight sky, when much of its glare is cancelled by daylight.

Whenever Venus is close to elongation, we begin to hear many reports of UFOs in the western sky. Venus is so bright that even experienced stargazers are sometimes taken by surprise.

Over the next few weeks, Venus will begin to move closer to the sun at twilight, actually passing between Earth and sun on August 15.

Most of the planets are so small and far away that they appear as star-like dots in most binoculars. Venus is the exception to this. Study it closely with binoculars over the next few weeks, and you will see it first as a tiny half-moon, then gradually getting larger in size but with a thinner crescent shape as it draws nearer the Earth.

Because Venus’ orbit has a slightly different tilt than Earth’s orbit, Venus usually passes above or below the sun, rather than passing directly in front of it. This August it will pass just 8 degrees south of the sun.

Twice so far this century, the orbits of Earth and Venus crossed with both planets in exactly the right position, and Venus was visible in front of the sun. Unfortunately the next such transit of Venus will not occur until the year 2117. I was lucky enough to have clear skies for both the transits of Venus in 2004 and 2012, and seeing the tiny black dot of Venus through a solar filter was a highlight of my observing life.

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app for iOS and Android.  It is available for mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

Night Sky Tour: The Summer Sky

Summer is upon us and observing the summer Milky Way is one of the simple joys for night sky enthusiasts. Find out what other sights await you on a clear summer night.

The Summer Triangle

The Summer Triangle dominates the summer sky. It crosses the hazy band of the Milky Way, which is split into two near the star Deneb by a large dust cloud called the Cygnus Rift.

The Summer Triangle.

The points of the triangle are three of the brightest stars in the summer sky, each the brightest star in its own constellation. The brightest is Vega, in Lyra; second is Altair, in Aquila; and third is Deneb, in Cygnus. Even city-dwellers with glowing, light-polluted skies can find the Summer Triangle.

Using the Big Dipper as the guide to the other stars and constellations, imagine a line extending 75 degrees of sky from the two bowl stars closest to the handle, to a point in the middle of the Summer Triangle. Stretch out your arm out at full length and measure about three spread hands from little finger to thumb. Each hand covers about 25 degrees of sky.

The Harp of the Gods

Vega is the brightest star in the triangle and is almost directly overhead in the summer. Contrary to what you might have seen in the movie Contact, no signs of an extraterrestrial civilization have been detected around this hot star—at least not yet.

Lyra, the Harp.

The name Vega comes from the Arabic word meaning swooping eagle or vulture. Vega is the luminary of Lyra, the Harp, a small but prominent constellation that is home to the Ring Nebula and the star Epsilon Lyrae. In mythology, Orpheus led Eurydice back from the underworld by charming the guards of the underworld with the music of his harp.

M57, the Ring Nebula.

The Ring Nebula is a luminous shell of gas that was ejected from an old star. It resembles a smoke ring or doughnut. Epsilon Lyrae appears to the naked eye as a double star, but through a small telescope you can see that the two individual stars are themselves double! Epsilon Lyrae is popularly known as the "double double."

Vega is a hydrogen-burning dwarf star, 54 times as luminous and 1.5 times as massive as the sun. It's relatively close to us, 25 light-years away.

The Eagle of Zeus

Once you have found Vega, look down to the south-southeast and you will see Altair in the constellation Aquila (the Eagle).

Aquila, the Eagle.

Altair spins at an amazing 750,000 kilometers (470,000 miles) per hour. This rotation has stretched Altair into an egg shape, wider than it is tall.

Altair is one of our nearest neighbors, 16 light-years away.

The Northern Cross

The most prominent constellation that forms part of the Summer Triangle is Cygnus. The main stars in Cygnus create a pattern in the sky known as the Northern Cross, with Deneb at the top. 

Cygnus, the Swan.

Cygnus is in an area of the Milky Way that contains many objects easily seen with an amateur telescope, including a beautiful red and blue double star at the base of the cross, Albireo.

The Strong Man of the Heavens

Imagine drawing a line from Phecda, the star on the bottom of the bowl of the Big Dipper closest to the handle, and continuing through Mizar, the star at the bend of the handle. It will pass by the constellation Hercules. Using Mizar as your starting point, stretch your arm out at full length and measure about two spread hands from little finger to thumb.

Hercules, the Hero.

Hercules is an ancient and faint constellation devoid of bright stars, such as those forming the Summer Triangle. Four of its main stars form a trapezoidal asterism called "the Keystone." On one side of the Keystone is a beautiful globular cluster—a stellar ball containing several hundred thousand stars. 

The Hercules Cluster (M13).

The Hercules cluster—also named Messier 13 or simply M13—is one of the sky's most beautiful sights and the finest globular cluster in the Northern Hemisphere. It is visible with the unaided eye by observers far removed from a city's glow. In binoculars, M13 looks like a fuzzy star; it's one of the more spectacular objects in the sky when seen through a telescope.

Edmond Halley, better known for predicting the return of the comet that still bears his name, discovered the Hercules Cluster.

M13 was selected as a target for one of the first radio messages broadcast to extraterrestrials from the Arecibo Observatory in Puerto Rico. If alien civilizations exist in the Great Hercules Cluster, we won't receive their reply for 50,000 years, because M13 is 25,000 light-years from Earth.

The Summer Milky Way

Summer nights offer the best time to explore our own Milky Way, a ribbon of pale light, formed by the combined light of billions of stars, that in summer stretches across the entire sky from northeast to southwest.

The Summer MilkyWay.

As summer comes on, the view gets exciting. We are treated to glowing clouds of dust, dark rifts, and star clusters as we look at our galaxy edge-on. Think of it as a flattened pancake of stars, seen on its edge.

The Milky Way is one of the most remarkable naked-eye sights in good dark skies far removed from the bright glows of civilization. You should be able to see the Cygnus Rift, a dark lane in the Milky Way between the constellations Cygnus and Scutum. The Cygnus Rift is not a hole in the Milky Way but rather a cloud of dust that obscures the view of distant stars.

Scanning with binoculars unveils the misty band of the Milky Way and reveals a sparkling river of thousands of stars. The most interesting regions stretch from the Summer Triangle toward the south-southeastern horizon.

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app for iOS and Android.  It is available for mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

Sky Events For June 2015

Moon Phases

Full Moon

Tuesday, June 2, 12:19 p.m. EDT

The Full Moon of June is known as the “Mead Moon,” “Strawberry Moon,”  “Rose Moon,” or “Thunder Moon.” It rises around sunset and sets around sunrise; this is the only night in the month when the Moon is in the sky all night long. The rest of the month, the Moon spends at least some time in the daytime sky.

Last Quarter Moon

Tuesday, June 9, 11:42 a.m. EDT

The Last Quarter Moon rises around 1:15 a.m. and sets around 1:15 p.m. It is most easily seen just after sunrise in the southern sky.

New Moon

Tuesday, June 16, 10:05 a.m. EDT

The Moon is not visible on the date of New Moon because it is too close to the Sun, but can be seen low in the East as a narrow crescent a morning or two before, just before sunrise. It is visible low in the West an evening or two after New Moon.

First Quarter Moon

Wednesday, June 24, 5:03 a.m. EDT

The First Quarter Moon rises around 12:30 p.m. and sets around 1:15 a.m. It dominates the evening sky.

Observing Highlights

Double shadow transit on Jupiter

Thursday, June 4, 12:58–2:13 a.m. EDT

The shadows of Io and Ganymede will simultaneously fall on the face of of Jupiter.

Venus at greatest elongation east

Saturday, June 6, evening twilight

Venus reaches its greatest eastward distance from the sun, its orbit shown in white here. It is closing in on Jupiter.

Pallas at opposition

Thursday, June 11, 9 p.m. EDT

Pallas, the second largest asteroid, will be in opposition to the Sun. At magnitude 9.4, it will be located just south of Lambda Hercules, below the “keystone” of Hercules.

Uranus and the Moon

Thursday/Friday, June 11/12

The Moon will be close to Uranus just before sunrise. In southern Australia and the South Pacific Ocean, the Moon will actually occult Uranus, as seen here from Melbourne, Australia.

Mercury and the Moon

Monday, June 15, sunrise

As seen here from Sri Lanka, the Moon will occult the planet Mercury. Other parts of the world will see the thin crescent of Mercury very close to the thin crescent of the moon just before sunrise.

Aldebaran and the Moon

Monday, June 15, sunrise

As seen here from eastern North America, the Moon will occult the bright red giant star Aldebaran.

Solstice

Sunday, June 21, 12:38 p.m. EDT

The sun reaches its most northern point, marking the middle of the astronomical summer season in the Northern Hemisphere, and winter in the Southern Hemisphere. The actual seasons tend to lag behind the astronomical seasons by about 6 weeks.

Mercury at greatest elongation west

Wednesday, June 24, dawn

Mercury will be at its farthest from the sun, and close to the red giant star Aldebaran.

Venus and Jupiter within 0.3 degrees

Tuesday, June 30, dusk

Venus and Jupiter will pass really close to each other, appearing within the same telescope field. Both will be 32 arc seconds in diameter, but Jupiter is much further away from both the Earth and the sun, so will be much fainter than Venus.

Planets

 Mercury is well placed in the eastern sky at dawn. It is better placed for observers in the Southern Hemisphere.

Venus shines high in the western sky after sunset, reaching its greatest elongation from the sun on June 6.

Mars is too close to the Sun to be visible. It will be in conjunction with the sun on June 14.

Jupiter is low in the western evening sky all month, closing in on Venus.

Saturn is just past opposition and shining brightly in Libra all night.

Uranus is in the eastern morning sky in Pisces.

Neptune rises after midnight in the constellation Aquarius.

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

Where's Pluto? How to See it Through A Telescope

With NASA’s New Horizons probe zeroing in on Pluto, due to pass it on July 14, attention of astronomers all over the world is focusing in on Pluto.

Let’s leave aside the question of whether Pluto is the smallest planet of the Sun or the largest of the Kuiper Belt Objects, and agree that it is an interesting and mysterious member of the solar family.

Many amateur astronomers are interested in seeing Pluto with their own telescopes, and this is what we will discuss here. Pluto is at present around 14th magnitude, requiring a telescope with at least 8 inches (200mm) aperture to be seen. The good news is that it is traveling in front of a rich part of the Milky Way, so there will be plenty of guide-posts among the stars to help you find it. The bad news is that it is easily lost amongst those stars, because it will look no different from a 14th magnitude star.

With Starry Night, I have plotted a series of charts zooming in on this tiny target. The first chart is what you will see with naked eye and binoculars at 3 a.m. this week: the familiar “teapot” of Sagittarius. Use Ascella and Nunki in the “handle” of the teapot to locate the two 4th magnitude stars Omicron and Xi2 in your telescope.

With naked eye and binoculars, locate Pluto in relation to the well-known “teapot” asterism of Sagittarius. It is close to the stars Chi2 and Omicron Sagittarii, just north of the “handle” of the teapot.  Credit: Starry Night software.

Switch to a low power eyepiece to see the view in the second chart. To give you some idea of scale, this chart shows the position of the New Horizons probe, although it is too faint to be visible in even the most powerful telescopes on Earth.

With a low power eyepiece in your telescope, zero in on Xi2 and Omicron Sagittarii. Credit: Starry Night software.

Notice the wide triangle of 9th magnitude stars just below Pluto’s location which points to it. The left two stars of the triangle point to a wide pair of stars at about 10th magnitude, and these will serve as a reference to locate Pluto’s position in the third chart.

This chart shows the position of Pluto for the next eight nights, as seen in a high-power eyepiece. The left-most dot, labeled “Pluto,” is its position tonight at 3 a.m., the rightmost dot, its position on June 4. Remember that the date changes at midnight. Credit: Starry Night software.

The brown dots in this chart show Pluto’s position at 3 a.m. EDT on the nights of (from left to right) May 28 through June 4. These dates are for the second half of the night (after midnight), when the date has changed to the next day’s date.

Pluto will resemble a tiny star, and the only way to make sure you are looking at the right star is to make a careful plot of the stars in the field. Comparing positions the next night will tell you for sure which “star” is Pluto: It’s the one that has moved.

So, to positively identify Pluto, is essential to observe it on at least two successive nights.

Because of the great interest in Pluto with the impending fly-by of New Horizons, Simulation Curriculum has released a free app for iOS and Android called Pluto Safari. This will be updated with new information as the fly-by approaches.

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

Night Sky Tour: The Spring Sky

The spring is a wonderful time to observe. Learn what to look for in the spring night sky tour.

Your Celestial Guidepost

The Big Dipper is a great starting point to learn your way around the night sky; in spring it's conveniently overhead. The Big Dipper itself is not an official constellation but part of a larger constellation called Ursa Major (the Great Bear). Ancient cultures saw the Big Dipper's star pattern as a bear with a long tail. 

The orientation of the Big Dipper from mid-northern latitudes one hour after sunset.

The name originates from the dipper-shaped pattern formed by the seven main stars of the constellation, although observers with keen vision will see that Mizar, the second star from the end of the dipper's handle is, in fact, a double-star. Binoculars make it easier to split the pair.

The stars of the Big Dipper serve as a handy guide to other stars and constellations. The two stars that form the front part of the dipper's bowl point straight to Polaris, the North Star, and because Polaris marks the location of the celestial north pole, the other stars in the sky seem to turn counterclockwise around it. Find Polaris and you know which way is north!

The Little Dipper and Polaris as seen from mid-northern latitudes one hour after sunset.

Polaris itself marks the end of the handle of another dipper—the Little Dipper in Ursa Minor (the Little Bear). Wrapping around Polaris is the constellation Draco. The stars that form this constellation are associated with dragons in the mythologies of many different cultures. 

Earth's north pole has wandered over the millennia and so has pointed to different stars in different eras. Right now it points to Polaris, but one of Draco's stars, Thuban, was the North Star when the pyramids were built.

Arc to Arcturus...

The handle of the Big Dipper points to two of spring's brightest stars—Arcturus and Spica.

The Little Dipper and the star Arcturus as seen from mid-northern latitudes one hour after sunset.

Arcturus is the Alpha (meaning the brightest) star of the constellation Bootes (the Herdsman). Follow the arc of the handle of the Big Dipper until you come to a bright orange star. This is Arcturus, forming the point of a pattern of stars resembling a kite. 

Arcturus is a giant star, twice as massive and 215 times as bright as the sun. It takes 37 years for the light of Arcturus to reach us, so when we gaze at it, we're seeing the star as it looked 37 years ago.

Ancient astromers had measured the position of Arcturus for nearly 2,000 years, which gave Edmond Halley enough data, in 1718, to discover that it was slowly moving against the background stars of its constellation. Before this discovery of proper motion, the stars were thought to be permanently fixed in the sky. Today we know that all stars move, but Arcturus moves much faster than most—about the width of the full moon every 800 years.

...and Speed on to Spica

If you keep following the arc of the handle of the Big Dipper past Arcturus, you'll encounter another bright star, Spica. Keep them straight by remembering this phrase: "Arc to Arcturus and speed on to Spica."

Polaris to Arcturus and on to Spica as seen from mid-northern latitudes one hour after sunset.

Spica resides in the constellation Virgo (the Virgin), a large zodiacal constellation that over time has represented almost every major female deity.

The Prominent Constellation of Spring

The most prominent constellation in the cool evenings of spring is Leo (the Lion).

Leo as seen from mid-northern latitudes one hour after sunset.

To find Polaris, you used the front of the bowl. To find Leo, you need to draw a line through the stars at the back of the bowl—away from Polaris. Stretch out your arm to its full length and measure about three fist-widths from Phecda—the star at the bottom of the bowl. This should put you at a point within the constellation of Leo.

Leo is a constellation of the Zodiac whose main stars have been included in many different mythologies. Stars depicting the mane and head of Leo form a pattern of stars resembling a sickle or a backward question-mark.The brightest star in Leo is Regulus, marking the end of the handle of the sickle or the dot in the question-mark. Regulus, Arcturus, and Spica are the three brightest stars of spring.

The Leonids meteor shower radiates from this constellation around mid-November.

A Beehive of Stars

To the side of Leo is the fainter constellation of Cancer (the Crab).

The Beehive Cluster in Cancer as seen from mid-northern latitudes one hour after sunset.

M44, the Beehive Cluster.

Inside the boundaries of Cancer is a group of stars neatly tucked together into a beehive shape. The Beehive Cluster (also known as Messier 44) was first described by Galileo, but it has been known since antiquity. 

The beehive is easily visible to the unaided eye as a faint round patch of light. Through binoculars, it resembles a swarm of bees.

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

SkyWatching: Shadow Play on Jupiter

Jupiter’s rapidly moving moons constantly surprise us with their dance around the giant planet. There will be two spectacular shadow plays this week.

Jupiter’s moons are very small, even in a large telescope, but their shadows are slightly larger, and can often be seen crossing Jupiter’s face with a good amateur telescope. I’ve seen the shadows with telescopes as small as 90mm aperture, but a telescope with 6-inch or larger aperture will show them much more clearly. Steady atmospheric seeing is also essential.

If you live on the eastern seaboard, look for Jupiter just after sunset on Wednesday, May 20 around 8:10 p.m. EDT. The first thing you will notice is that only two of Jupiter’s usual four moons are visible. That’s because two of the Moons, Io and Callisto, are in front of Jupiter’s disk, and are said to be “in transit.” You probably won’t see Io, because its color and brightness blend in so well with the cloud tops behind it. You may be able to see Callisto because its dark surface stands out against Jupiter’s bright clouds. I usually see it as a tiny greyish spot. Look more closely, and you’ll see two small dark shadows on Jupiter’s face. One of these is Io’s shadow, but the other is not the shadow of Callisto. Instead it is the shadow of Ganymede, off to Jupiter’s right. That’s because of the angle at which the sun is illuminating the tableau. 

On Wednesday night, May 20, the shadows of Jupiter’s moons Ganymede and Io will cross Jupiter’s face. This shows the shadows at 8:10 p.m. EDT, just after Io’s shadow has started across, and just before Ganymede’s shadow leaves.  Credit: Starry Night software.

Take another look later in the evening, around 9:55 p.m., and you’ll see that Ganymede’s shadow has left the disk and that Io’s shadow is about to be hidden behind Callisto. This will be the first time I have ever seen a moon’s shadow eclipsed by another moon. 

Nearly two hours later at 9:55 p.m., Ganymede’s shadow has left, and Io’s shadow is about to be eclipsed by the moon Callisto. The Great Red Spot is well placed close to Jupiter’s central meridian. Credit: Starry Night software.

Also keep a lookout for the Great Red Spot, though it is not nearly as “great” nor as “red” as it once was. It’s more usually seen as a light notch in the North edge of Jupiter’s South Equatorial Belt. At moments of steady seeing, its salmon pink color may appear briefly.

A week later on May 27, the situation nearly repeats itself, but is about two hours later, making it more easily seen across the whole of North America. Ganymede’s shadow starts across Jupiter’s face at 8:58 p.m. EDT. Io’s shadow follows at 10:01 p.m., and both shadows are present until Io’s shadow leaves at 12:18 a.m., followed by Ganymede’s at 12:34 a.m. 

Exactly a week later, on Wednesday, May 27 at 10:05 p.m., the pattern repeats, except that the shadows are closer together and Callisto is no longer in front of Jupiter. Credit: Starry Night software.

Notice that at around 11:48 p.m., Io’s faster moving shadow actually passes Ganymede’s, and the two shadows merge.

At 11:48 p.m., Io’s faster moving shadow catches up with Ganymede’s, and the two shadows merge. Again, the Great Red Spot is well placed. Credit: Starry Night software.

Once again, the Great Red Spot should be in evidence.

If you live west of the Eastern time zone, be sure to subtract the appropriate corrections from the times given above: 1 hour for CDT, 2 hours for MDT, and 3 hours for PDT.

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First Night Out Series: How The Stars Got Their Names

Humans have been naming the stars for millennia. The brightest stars were named long ago by people who immortalized their folklore in the heavens, and many of their names are still used today.

Centuries later, formal and systematic naming systems were developed when more extensive lists of stars were compiled.

The following sections describe in more detail how the stars received their names over the years.

Common Names

You might have heard of some of the more popular stars, such as Sirius, Betelgeuse, and Polaris. These names sound foreign, and they are—their origins are mostly Arabic translations of Latin descriptions.

Common names. Credit: Starry Night software.

But to add to the confusion, scribes in the Middle Ages reproduced astronomical manuscripts by hand—a method that introduced errors, especially when copying words they did not know. Over time, the process of making copies of copies made it harder to decipher the original meaning of some words. 

The common names for the brightest stars in the sky date back to ancient myths. Stars were often named after heroes, animals, or components of the constellations they helped form. The folklore of the stars offers a tantalizing glimpse into the associations ancient peoples established with the stars.

In all, about 900 stars have common names primarily of Arabic, Greek, or Latin origin. A few star names are relatively modern, however, invented as recently as the 20th century.

A few examples of common names are Sirius (Greek for scorching), Thuban (corrupted Arabic for serpent's head), and Betelgeuse, (a copying error from yad al-jauza, meaning the hand of al-Jauza, the "Central One").

The Bayer System

Johann Bayer was a German lawyer and uranographer. He was born in Rain, Lower Bavaria, in 1572. 

Johann Bayer was a German lawyer and uranographer. He was born in Rain, Lower Bavaria, in 1572. 

Common names are handy for identifying the brightest stars in the sky, but astronomers needed a system for naming all the stars in the sky, including even the faintest ones.

The Bayer system is the first of two naming systems that incorporate constellation names into the identification of stars. It names the brightest stars by assigning a Greek letter (Alpha, Beta, Gamma, Delta, and so on) in an approximate order of decreasing brightness, along with the Latin possessive name of the constellation in which the star resides.

Bayer Names. Credit: Starry Night software.

In this system, Sirius, which is in the constellation Canis Major, is known as Alpha Canis Majoris. Betelgeuse, which resides in the constellation Orion, is known as Alpha Orionis.

The ordering of stars by brightness in the Bayer system is only approximate. As an example, Rigel's name according to the Bayer system is Beta Orionis, suggesting it's the star in Orion just dimmer than Betelgeuse—but it's actually brighter. Brightness fluctuations in Betelgeuse make it brighter than Rigel at times, such as when the system was first introduced in 1603.

The Flamsteed System

John Flamsteed was an English astronomer and the first Astronomer Royal. He catalogued over 3,000 stars.

John Flamsteed was an English astronomer and the first Astronomer Royal. He catalogued over 3,000 stars.

The second system that uses the constellations in which the stars reside is the Flamsteed system.

The Bayer system was useful for naming the stars—certainly better than using common names—but it had problems. The first was that of fluctuating brightness, as in the case of Betelgeuse and Rigel. The second problem was that there are only so many letters in the Greek alphabet.

Unlike the Bayer system, the Flamsteed system can be used to name an unlimited number of stars. In this system, we still use the Latin possessive name of a star's constellation, but this time the stars are distinguished not by their brightness, but also by their proximity to the western edge of their constellations.

Flamsteed Names. Credit: Starry Night software.

The star closest to the western edge is assigned the number 1; the second-closest star to the western edge is number 2, and so on.

For example, the star Sirius is called Alpha Canis Majoris in the Bayer system and 9 Canis Majoris in the Flamsteed system, meaning that it is the ninth-closest star to the western edge of the constellation Canis Major.

Catalog Names

The faintest of stars are known only by their identifiers in specialized catalogs. These catalogs can contain billions of stars, from the brightest to the very faintest, which can be seen only with powerful telescopes and long exposures.

Catalog Names. Credit: Starry Night software.

For example, Sirius is bright enough to have a poetic common name, descriptive Bayer and Flamsteed names, and the label HIP32349 in the Hipparcos catalog.

Naming Your Own Star

You may have read that you can buy a star, or invest in real estate on the moon or Mars.

Some companies provide this service to raise funds for science or a charity but others do it only to line their own pockets. Please do your research and be aware that although these companies charge you a fee for an official-looking certificate, these services have no formal validity at all. The scientific community only recognizes naming conventions based on the regulations of the International Astronomical Union (IAU). 

Remember that the beauty of the night sky is not for sale, and it is free for everyone to enjoy.

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram. 

The Ten Brightest Stars In The Sky

From our corner of the galaxy, these stars are the most brilliant signposts in the heavens and can be enjoyed even from the light-polluted hearts of major cities.

Sirius

All stars shine but none do it like Sirius, the brightest star in the night sky. Aptly named, Sirius comes from the Greek word Seirius, meaning, "searing" or "scorching." Blazing at magnitude -1.42, it's twice as bright as any star in our sky besides the Sun.

Sirius resides in the constellation Canis Major, the Big Dog, and is commonly called the Dog Star. In ancient Greece the dawn rising of Sirius marked the hottest part of summer—the season's "dog days."

Sirius no longer marks the hottest part of summer, because it now rises later in the year. This happens because the Earth has been wobbling slowly around its axis in a 25,800-year cycle. This wobble—called precession—is caused by the gravitational attraction of the Moon on Earth's equatorial bulge, and it gradually changes the locations of stars on the celestial sphere. 

The best time to see Sirius is probably in winter (for northern-hemisphere observers), because it rises fairly early in the evening. To find the Dog Star, use the constellation Orion as a guide. Follow the three belt stars 20 degrees southeast to the brightest star in the sky. Your fist at arm's length covers about 10 degrees of sky, so it's about two fist-widths down.

Sirius, the red giant star Betelgeuse, and Procyon in Canis Minor form a popular asterism known as the Winter Triangle.

Sirius is 23 times as luminous as the Sun, and about twice the mass and diameter. At a mere 8.5 light-years away from Earth, Sirius seems so bright in part because it's the fifth-closest star to the Sun.

The brilliance of Sirius illuminates not only our night skies, but also our understanding. While observing it in 1718, Edmond Halley (of comet fame) discovered that stars move in relation to one another—a principle now known as proper motion. 

This Hubble Space Telescope image shows Sirius A, the brightest star in our nighttime sky, along with its faint, tiny stellar companion, Sirius B.

In 1844, the German astronomer Friedrich Bessel observed that Sirius had a wobble, as if it were being tugged by a companion star. And in 1862, Alvan Clark solved this mystery (while testing his new 18.5-inch lens, the largest refracting telescope in the world at that time). Clark discovered that Sirius was not one star but two.

This proved to be the first discovery in what became a whole class of stars: the compact stellar remnant or white dwarf. These are stars that, once depleting all their hydrogen, collapse to a very dense core. Astronomers have calculated that Sirius's companion—dubbed Sirius B—contains the mass of the Sun in a package as small as the Earth. 

Sixteen milliliters of matter from Sirius B (that is, about one cubic inch of the stuff) would weigh 2000 kilograms on Earth.

At magnitude 8.5, it is one four-hundredth as luminous as the Sun. The brighter and larger companion is now known as Sirius A.

Canopus

Canopus resides in the constellation Carina, the Keel. Carina is one of three modern-day constellations that once formed the ancient constellation of Argo Navis, named for the ship Jason and the Argonauts sailed in to search for the Golden Fleece. Two other constellations form the sail (Vela) and the stern (Puppis). 

In modern odysseys, spacecraft like Voyager 2 used the light from Canopus to orient themselves in the sea of space.

Canopus is a true powerhouse. Its brilliance is due more to its great luminosity than its proximity. This number two on our list of stars has 14,800 times the intrinsic luminosity of the Sun! But at 316 light-years away, it's more than 37 times as far from us as the number one star, Sirius.

With a magnitude of minus-0.72, Canopus is easy to find in the night sky, though it is only visible at latitudes south of 37 degrees north. 

To catch a glimpse of it from middle-latitude or southern locations in the United States, look for a bright star low on the southern horizon during the winter months. Canopus is 36 degrees below the brightest star in the sky, Sirius. The further south you are, the better your view will be.

Canopus is a yellow-white F super giant—a star with a temperature from 5,500 to 7,800 degrees Celsius (10,000 to 14,000 degrees Fahrenheit)—that has stopped hydrogen fusion and is now converting its core helium into carbon. This process has led to its current size, 65 times that of the Sun. If we were to replace our Sun with Canopus, it would nearly envelop Mercury. 

Canopus will eventually become one of the largest white dwarfs in the galaxy and might just be massive enough to fuse its carbon, turning into a rare neon-oxygen white dwarf. These are rare because most white dwarfs have carbon-oxygen cores, but a massive star like Canopus can begin to burn its carbon into neon and oxygen as it evolves into a small, dense, and cooler object.

Canopus lost its place in the celestial hierarchy for a short time in the 1800s when the star Eta Carinae underwent a massive outburst, surpassing Canopus in brightness and briefly becoming the second-brightest star in the sky. And Eta Carinae may yet outdo even Sirius, the brightest. It is fated to become a supernova, perhaps very soon in cosmic time-terms: within a few hundred thousand years.

Alpha Centauri

Alpha Centauri (or Rigel Kentaurus, as it is also known) is actually a system of three stars gravitationally bound together. The two main stars are Alpha Centauri A and Alpha Centauri B. The tiniest star in the system is Alpha Centauri C, a red dwarf. 

The Alpha Centauri system is a special one. At an average distance from us of 4.3 light-years, these stars are our nearest known stellar neighbors. 

A comparison of the sizes and colors of the stars in the Alpha Centauri system with the Sun. 

​Centauri A and B are remarkably Sun-like, with Centauri A a near twin of the Sun (both are yellow G stars). In comparison to the Sun, Alpha Centauri A is 1.5 times as luminous and shines at magnitude -0.01 while Alpha Centauri B is half as luminous and shines at magnitude 1.3.

Alpha Centauri C is one seven-thousandth as bright and shines at eleventh magnitude. 

Of the three stars, the smallest is the closest to the Sun, 4.22 light-years away. Because of its proximity, it is known as Proxima Centauri.

When night falls and the skies are clear in summer, the Alpha Centauri system shines at a magnitude of minus-0.27, low in the southern sky. You can find it at the foot of the Centaur in the constellation Centaurus. 

Because of its position in the sky, the Alpha Centauri system is not easily visible in much of the northern hemisphere. An observer must be at latitudes south of 28 degrees north (or roughly from Naples, Florida and locations further south) to see the closest stellar system to us. 

The two brighter components of the system make a wonderful double star to observe in a small telescope.

Naked-eye Alpha Centauri appears so bright because it is so close. This also means that it has a large proper motion—the drifting of stars relative to each other due to their actual movements in space. In another 4,000 years, Alpha Centauri will have moved near enough to Beta Centauri for the two to form an apparent double star.

Arcturus

Arcturus is the brightest star in the northern celestial hemisphere. (The first three stars on this list are actually in the southern celestial sphere, though seasonally they are visible from the northern hemisphere of Earth).

Known as the Bear Watcher, Arcturus follows Ursa Major, the Great Bear, around the north celestial pole. The name itself derives from the Greek word arktos, meaning bear.

Arcturus is an orange giant, twice as massive and 215 times as bright as the Sun. It takes 37 years for the light of Arcturus to reach us, so when we gaze upon it, we are seeing the star as it looked 37 years ago. It glows at magnitude -0.04 in our night sky.

A variable star, Arcturus is in the last stages of life. 

During its internal struggle between gravity and pressure, Arcturus has swelled to 25 times the Sun's diameter. 

Eventually the outer envelope of Arcturus will peel away as a planetary nebula, similar to the famed Ring Nebula (M57) in Lyra. The star left behind will be a white dwarf.

Arcturus is the alpha (meaning brightest) star of the springtime constellation Bootes, the Herdsman. You can find it by using the Big Dipper as your celestial guidepost. Follow the arc of the handle until you come to a bright orange star. This is Arcturus, forming the point of a pattern of stars resembling a kite. 

In the spring, if you keep following the arc, you'll encounter another bright star, Spica. (Keep it straight by remembering the phrase: "Arc to Arcturus, speed on to Spica.")

In the 1930s, astronomers were busy measuring the distance to nearby stars and determined—incorrectly, it turned out—that Arcturus was 40 light-years from Earth. During the 1933 World's Fair in Chicago, the light from Arcturus was collected with new photocell technology and used to activate a series of switches. Light believed to have originated at the time of the previous Chicago World's Fair 40 years earlier was used to illuminate and officially open the fair in 1933.

The science of astronomy progresses, and we now know that Arcturus is only 37 light-years away.

Vega

The name Vega comes from the Arabic word for "swooping eagle" or "vulture." Vega is the luminary of Lyra, the Harp, a small but prominent constellation that is home to the Ring Nebula (M57) and the star Epsilon Lyrae. 

The ring is a luminous shell of gas resembling a smoke ring or a doughnut that was ejected from an old star. Epsilon Lyrae appears to the naked eye as a double star, but through a small telescope you can see that each of the two individual stars is itself a double! Epsilon Lyrae is popularly known as the "double double."

Vega is a hydrogen-burning dwarf star, 54 times as luminous and 1.5 times as massive as the Sun. At 25 light-years away, it is relatively close to us, shining with a magnitude of 0.03 in the night sky. 

In 1984, a disk of cool gas surrounding Vega was discovered—the first of its kind—extending 70 AU from the star, roughly the distance from our Sun to the edge of the Kuiper Belt. This discovery's important because a similar disk is theorized to have played an integral role in planet development within our own solar system. 

Astronomers also found a "hole" in the Vega disk, indicating the possibility that planets might have already coalesced and formed around the star. This led the astronomer and author Carl Sagan to choose Vega as the source of advanced alien radio transmissions in Contact, his first science-fiction novel. (In real life, no such transmissions have ever been detected.)

Together with the bright stars Altair and Deneb, Vega forms the popular Summer Triangle asterism that announces the beginning of summer in the northern hemisphere. The asterism crosses the hazy band of the Milky Way, which is split in two near Deneb by a large dust cloud called the Cygnus Rift. 

This area of the sky is ideal for sweeping with binoculars of any size in dark-sky conditions.

Vega was the first star to be photographed, on the night of July 16, 1850, by the photographer J.A. Whipple. With the daguerreotype camera used at the time, he made an exposure of 100 seconds using a 15-inch refractor telescope at Harvard University. Fainter stars (those of second magnitude and dimmer) would not have registered at all using the technology of the time.

Vega used to be the North Star, but 12,000 years of Earth's precession has altered its place in the celestial sphere. In another 14,000 years, Vega will be the North Star again.

Capella

Capella is the primary star in the constellation Auriga (the Charioteer), and the brightest star near to the north celestial pole. 

Capella is actually a fascinating star system of four stars: two similar class-G yellow-giant stars and a pair of much fainter red-dwarf stars. The brighter yellow giant, known as Aa, is 80 times as luminous and nearly three times as massive as the Sun. The fainter yellow giant, known as Ab, is 50 times as luminous as the Sun and two-and-a-half times as massive. The combined luminosity of the two stars is the equivalent of about 130 Suns.

The Capella system is 42 light-years away, its light reaching us with a magnitude of 0.08. 

It is highest in the winter months and circumpolar (meaning it never sets) at latitudes higher than 44 degrees north (or roughly north of Toronto, Canada).

To locate it, follow the two top stars that form the pan of the Big Dipper across the sky. Capella is the brighter star in the irregular pentagon formed by the stars in the constellation Auriga.

South of Capella is a small triangle of stars known as the Kids. One of the most ancient legends had Auriga as a goat herder and patron of shepherds. The brilliant golden yellow Capella was known as the "She-Goat Star." The nearby triangle of fainter stars represents her three kids.

Both yellow giants are dying, and will eventually become a pair of white-dwarf stars.

Rigel

On the western heel of Orion, the Hunter, rests brilliant Rigel. In myth, Rigel marks the spot where Scorpio, the Scorpion, stung Orion after a brief but fierce battle. Its Arabic name means the Foot.

Rigel is a multiple-star system. The brighter component, Rigel A, is a blue supergiant that shines a remarkable 40,000 times stronger than the Sun! Although it's 775 light-years distant, its light shines bright in our evening skies, at magnitude 0.12.

Rigel resides in the most impressive of the winter constellations, mighty Orion. After the Big Dipper, it's the most-recognized and easiest-to-identify constellation. It helps that the shape made by Orion's stars closely matches the shape of a human hunter: three bright stars are lined up together to form a belt, the other four stars surrounding the belt compose shoulders and legs.

Telescope observers should be able to resolve Rigel's companion, a fairly bright seventh-magnitude star. But the jewel in Orion is the Great Orion Nebula (M42), a vast stellar nursery where new stars are still being born. It can be found six moon-widths south of the belt stars.

A heavy star of 17 solar masses, Rigel is likely to go out with a supernova-sized bang one day. Or it might become a rare oxygen-neon white dwarf.

Procyon

Procyon resides in the small constellation of Canis Minor, the Little Dog. The constellation symbolizes the smaller of Orion's two hunting dogs (the other is, of course, Canis Major). 

The word procyon is Greek for "before the dog," for in the northern hemisphere, Procyon announces the rise of Sirius, the Dog Star.

Procyon is a yellow-white, main-sequence star, twice the size and seven times as luminous as the Sun. Like Alpha Centauri, it appears so bright because at 11.4 light-years, it is relatively close.

Procyon is an example of a main sequence subgiant star, one that is starting to die as it converts its remaining core hydrogen into helium. Procyon is currently twice the diameter of the Sun, one of the largest stars within 20 light-years.

Canis Major can be found fairly easily east of Orion during northern-hemisphere winter. Procyon, along with Sirius and Betelgeuse, form the Winter Triangle asterism.

Procyon is orbited by a white-dwarf companion detected visually in 1896 by John M. Schaeberle. The fainter companion's existence was first noted in 1840, however, by Arthur von Auswers, who observed irregularities in Procyon's proper motion that were best explained by a massive and dim companion. 

At just one-third the size of Earth, the companion dubbed Procyon B has the equivalent of 60 percent of the Sun's mass. The brighter component is now known as Procyon A.

Achernar

Achernar is derived from the Arabic phrase meaning "the end of the river," an appropriate name for a star that marks the southernmost flow of the constellation Eridanus, the River.

Achernar is the hottest star on this list. Its temperature has been measured to be between 13,000 and 19,000 degrees Celsius (24,700 and 33,700 Fahrenheit). Its luminosity ranges from 2,900 to 5,400 times that of the Sun. Shining at magnitude 0.45, its light takes 144 years to reach your eye. 

Achernar is more or less tied with Betelgeuse (number ten on this list) for brightness. However, Achernar is generally listed as the ninth-brightest star in the sky because Betelgeuse is a variable whose magnitude can drop to less than 1.2, as was the case in 1927 and 1941.

For northern-hemisphere observers, Achernar rises in the southeast during the winter months and is visible only from latitudes south of 32 degrees north; those further north only see a portion of the constellation. 

(For Star Trek fans, the constellation of Eridanus is also home to Epsilon Eridanus, the star around which Mr. Spock's imaginary home planet of Vulcan supposedly revolves!)

Achernar is a massive class-B star containing up to eight solar masses. It is currently burning its hydrogen into helium and will eventually evolve into a white dwarf star.

Betelgeuse

Don't let Betelgeuse's ranking as the tenth-brightest star in the sky fool you. Its distance—430 light-years—hides the true scale of this supergiant. With a whopping luminosity of 55,000 suns, Betelgeuse still shines bright in our skies at a magnitude of 0.5.

Betelgeuse (pronounced "beetle juice" by most astronomers) derives its name from an Arabic phrase meaning "the armpit of the central one." 

Image from ESO's Very Large Telescope showing the stellar disk.

The star marks the eastern shoulder of mighty Orion, the Hunter. Another name for Betelgeuse is Alpha Orionis, indicating that it's the brightest star in the winter constellation of Orion. But Rigel (Beta Orionis) is actually brighter. This misclassification probably happened because Betelgeuse is a variable star (a star that changes brightness over time) and it might have been brighter than Rigel when Johannes Bayer originally categorized it. 

Betelgeuse is an M1 red supergiant, 650 times the diameter and about 15 times the mass of the Sun. If Betelgeuse were to replace the Sun, all the planets out to the orbit of Mars would be engulfed! 

Observe Betelgeuse and you are witnessing a star approaching the end of its long life. Its huge mass suggests that it might fuse elements all the way to iron. If so, it will blow up as a supernova that would be as bright as a crescent moon, as seen from Earth. A dense neutron starwould be left behind. The other possibility is that it might evolve into a rare neon-oxygen dwarf. 

Betelgeuse was the first star to have its surface directly imaged, a feat accomplished in 1996 with the Hubble Space Telescope.

Perhaps a much more advanced orbiting telescope will be watching someday when Betelgeuse goes supernova, an event which will certainly make it the brightest star in Earth's skies—if only for a few months.

If you'd like to follow along with NASA's New Horizons Mission to Pluto and the Kuiper Belt, please download our FREE Pluto Safari app.  It is available for iOS and Android mobile devices. Simulate the July 14, 2015 flyby of Pluto, get regular mission news updates, and learn the history of Pluto.

Simulation Curriculum is the leader in space science curriculum solutions and the makers of Starry Night, SkySafari and Pluto Safari. Follow the mission to Pluto with us on Twitter @SkySafariAstro, Facebook and Instagram.