Falling Leaves And Autumn Skies

The autumn sky shows the transition from the summer Milky Way, through the “watery” constellations of autumn, to the bright stars of winter. Credit: Starry Night software.

Autumn is the favorite season for many skywatchers. You can get your last look at summer stars and, if you stay up late, your first look at winter stars. Best of all, it gets dark earlier and the night temperatures are still comfortable.

Our graphic this week shows a panorama of the sky looking south around 8 p.m., just after the sky becomes fully dark. After the change to standard time this weekend, this will be the view at around 7 p.m.

Looking towards the west, at the right in the graphic, you can see the familiar constellations of summer. Sagittarius and the core of the Milky Way Galaxy are setting in the southwest, while the summer triangle: Deneb, Vega, and Altair, shines overhead.

It’s not too late to revisit some of the popular summer objects: double stars Albireo and Epsilon Lyrae, the globular clusters in Hercules and Ophiuchus, the Ring Nebula in Lyra, and the bright nebulae and clusters of Sagittarius.

Looking south, the upside down triangle of Capricornus rides high. Its rightmost star, Algedi, is a naked-eye double. Above Capricornus, just to the left of Altair, is the tiny constellation Delphinus, the dolphin, one of the few constellations that actually looks like its name. It’s worth exploring the region between Altair and Albireo, where you will find two of the finest deep sky objects: Brocchi’s Cluster, popularly called “the coat hanger,” and the Dumbbell Nebula, one of the largest and brightest planetary nebulae.

Many of the constellations in the autumn sky have watery associations. These include Capricornus (the sea goat), Delphinus (the dolphin), Aquarius (the water bearer), Pisces (the fish, plural), Piscis Australis (the southern fish, singular), and Cetus (the whale). Most of these are lacking in bright stars, with the exception of Pisces Australis which contains the first magnitude star Fomalhaut, the first star to have one of its planets directly imaged by the Hubble Space Telescope.

Although Aquarius is dim in terms of stars, it contains a number of fine deep sky objects, including the globular cluster Messier 2, and two fine planetary nebulae, the small bright Saturn Nebula snd the huge Helix Nebula. The latter is probably the planetary nebula closest to the sun, about 700 light years distant, and as a result is very large in size, almost as large as the moon. Because of its large angular size, its light is spread out over a wide area, making it very hard to see. You will need a narrow band filter on your telescope to spot it. 

Off to the east, the Square of Pegasus dominates the sky. This consists of three stars in Pegasus with the fourth corner of the square being marked by Alpheratz, the brightest star in the constellation Andromeda, which trails away to the northeast.

Right in the upper left corner of the graphic are the two largest and brightest galaxies in our neighborhood, the Andromeda Galaxy and the Triangulum Galaxy. These are located symmetrically on either side of the second pair of stars eastward from Alpheratz in Andromeda.

The Andromeda Galaxy (to the north) is large and bright. If you live in a city, you will need binoculars to see it, but sharp-eyed observers in the country, including myself, have spotted it with their unaided eyes. The Triangulum Galaxy is almost as large, but nowhere near as bright as Andromeda. It is best seen in small binoculars. Oddly, it is very hard to see in the narrow field of a telescope because its dim light is spread across such a large area.

Finally, in the northeast you can see the first of the winter stars, the bright star Capella in Auriga and the brilliant Pleiades Cluster in Taurus. Soon Orion will arrive in the east, in the words of Robert Frost:

            You know Orion always comes up sideways.

            Throwing a leg up over our fence of mountains,

            And rising on his hands, he looks in on me…

 Stay up until midnight, and you will see him, too.

 

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.

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. 

First Night Out Series: Measuring Distances In The Sky

Measuring the distance from one star to another in the sky is easy when you master using your hands to measure the degrees between objects. 

Hold your hand at arm's length:

  • The width of your little finger is about one degree—enough to cover the moon and sun, both of which are each half a degree across.
  • The width of the first three fingers side-by-side spans about five degrees.
  • A closed fist is about ten degrees.
  • If you spread out your fingers, the distance from the tip of your first finger to the tip of your little finger is 15 degrees.
  • If you spread out your fingers, the distance from little finger to thumb covers about 25 degrees of sky.

Measuring degrees with your hands.

With a bit of practice, this hand system is endlessly useful when measuring your way around the sky.

Calibrating with the Big Dipper

Everyone's hands are slightly different, so you might want to practice and calibrate your own hand measurements using the Big Dipper.

Big Dipper Distances.

Here are the rough distances from Dubhe to several other prominent Big Dipper stars:

Dubhe to Merak 5 degrees
Dubhe to Megrez 10 degrees
Dubhe to Alioth 15 degrees
Dubhe to Mizar 20 degrees
Dubhe to Alkaid 25 degrees

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. 

Astronomical Audio Pronunciation Guide

Some astronomical monikers truly do seem alien, and ensuring correct pronunciation can be hazardous for even the most advanced educator. Starry Night Education is here to help with our Audio Pronunciation Guide for the top 500 most commonly mispronounced astronomical objects, from Acamar through Zubeneschamali.

Choose your category:
asteroids
constellations
planets
meteors
stars
Asteroids
Constellations
Planets & Moons
Meteor Showers
Stars

     
Click the name to hear the correct pronunciation.

Asteroids
 
 
Name
Pronunciation
 
ANN-FRANK
 
a-PAW-fis
 
a-STREE-a
 
BACK-us
 
BRAIL
 
SEER-eez
 
e-JEER-ee-a
 
EER-os
 
ewe-NOM-ee-a
 
FLOOR-a
 
for-TUNE-a
 
HEE-bee
 
hy-GEE-a
 
eye-REE-nee
 
EYE-ris
 
JEW-noe
 
ka-LYE-o-pee
 
lew-TEE-sha
 
ma-SALL-ee-a
 
mel-POM-e-nee
 
MEE-tis
 
PAL-as
 
par-THEN-o-pee
 
SYE-kee
 
SIL-vee-a
 
the-LYE-a
 
THEE-tis
 
VES-ta

Constellations
 
 
Name
 
Pronunciation
 
an-DROM-eh-da
 
ANT-lee-uh
 
APE-us
 
ack-KWAIR-ee-us
 
ack-WILL-lah
 
AY-rah
 
AIR-ease
 
or-EYE-gah
 
bow-OH-tease
 
SEE-lum
 
ca-MEL-oh-PAR-dal-iss
 
KAN-surr
 
KAN-es veh-NAT-ih-see
 
KANE-es MAY-jer
 
KANE-es MY-ner
 
CAP-rih-CORN-us
 
car-EE-na
 
KASS-ee-oh-PEE-ah
 
sen-TOR-us
 
SEE-fee-us
 
SEE-tus
 
kah-ME-lee-un
 
SIR-sin-us
 
ko-LUM-ba
 
CO-ma bare-uh-NYE-sees
 
coe-ROW--nah ow-STRAHL-iss
 
coe-ROW--nah BOR-ee-AL-iss
 
CORE-vuss
 
CRAY-ter
 
Kruks
 
SIG-nus
 
del-FYE-nus
 
doh-RAY-doh
 
DRAY-ko
 
eh-KWOO-lee-us
 
eh-RID-uh-nuss
 
FOR-naks
 
GEM-in-eye
 
GROOS
 
HER-kyou-leez
 
hor-uh-LOW-gee-um
 
HY-druh
 
HY-drus
 
IN-dus
 
la-SIR-ta
 
LEE-oh
 
LEE-oh MY-ner
 
LEE-puss
 
LEE-bra
 
LOUP-us
 
links
 
LIE-rah
 
MEN-sa
 
MY-krow-SKOH-pee-em
 
mon-OSS-er-us
 
MUSS-ka
 
NOR-ma
 
OCK-tens
 
Oaf-ih-YOU-kus
 
oh-RYE-un
 
PAY-vo
 
PEG-uh-suss
 
PURR-see-us
 
FEE-nix
 
PICK-tor
 
PIE-sees
 
PIE-sees oss-TREE-nus
 
PUP-iss
 
PICK-sis
 
reh-TICK-yuh-lum
 
suh-JIT-uh
 
sa-jih-TARE-ee-us
 
SKOR-pee-uss
 
SKULP-tor
 
SCOOT-um
 
SIR-pens CAP-ut
 
SIR-pens KAW-dah
 
SEX-tens
 
TOR-us
 
tell-es-SCOPE-ee-um
 
tri-ANG-yuh-lum
 
tri-ANG-yuh-lum aus-TRAY-lee
 
too-KAY-nah
 
URR-sah MAY-jer
 
URR-sah MY-ner
 
VEE-la
 
VER-go
 
VO-lans
 
vul-PECK-yoo-la

Planets & Moons
 
 
Name
Pronunciation
 
ah-DRAHS-tee-ah
 
et-NEE
 
ah-mal-THEE-ah
 
a-NAN-kee
 
AIR-ee-el
 
AT-lus
 
aw-TON-oe-ee
 
be-LIN-dah
 
bee-AHNK-uh
 
KAL-e-ban
 
ka-LIRR-o-ee
 
ka-LIS-toe
 
ka-LIP-soe
 
KAR-mee
 
kal-DEE-nee
 
CARE-en
 
core-DEAL-ya
 
KRESS-e-da
 
DYE-mos
 
DES-de-MOAN-a
 
de-SPEEN-a
 
dye-ON-ee
 
URTH
 
EE-lahr-ah
 
en-SELL-ah-dus
 
EPP-e-ME-thee-us
 
err-IN-o-mee
 
EE-ris
 
ewe-AN-thee
 
ewe-POUR-ee-e
 
you-ROE-pah
 
ewe-RID-o-mee
 
GAB-ree-ell
 
GAL-aTEA-a
 
GAN-eh-meed
 
har-PAL-e-kee
 
he-LEAN
 
her-MIP-ee
 
HIM-ah-lee-ah
 
hye-PER-ee-on
 
ee-AHP-eh-tus
Io
 
EYE-oh
 
EYE-o-KAS-tee
 
eye-SON-oe-ee
 
JAY-nus
 
JEW-lee-ette
 
JEW-pi-ter
 
KAY-lee
 
KAL-e-kee
 
la-RISS-a
 
LEE-dah
 
lis-ih-THEE-ah
 
MARZ
 
MEG-a-KLYE-tee
 
MIRK-you-ree
 
MEE-tis
 
MYE-mus
 
mi-RAN-dah
 
moon
 
NYE-ad
 
NEP-toon
 
NAIR-ee-id
 
OH-ba-ron
 
oh-FEEL-ya
 
or-THOE-see-e
Pan
 
PAN
 
pan-DOOR-ah
 
pa-SIF-ah-ee
 
PAS-e-thee
 
FOE-bos
 
FEE-bee
 
PLOO-toe
 
POR-sha
 
prak-SID-e-kee
 
pro-MEE-thee-us
 
PRO-per-oe
 
PRO-tee-us
 
PUCK
 
KWA-oh-ar
 
REE-a
 
ROS-a-lind
 
SA-turn
 
SET-e-bus
 
se-NO-pee
 
SPON-dee
 
ste-FAA-noe
Sun
 
sun
 
SICK-o-RACKS
 
tay-IJ-e-tee
 
tah-LES-toe
 
TEE-this
 
tha-LASS-a
 
THEE-bee
 
the-MISS-toe
 
Thy-OE-nee
 
TYE-tun
 
tye-TAIN-ee-ah
 
TRING-kew-loe
 
TRY-ton
 
UM-bree-el
 
YOU-rah-nus
 
VEE-nus

Meteor Showers
 
 
Name
Pronunciation
 
AY-tah AK-wa-rids
 
GEM-e-nids
 
LEE-o-nids
 
LYE-rids
 
north TOR-ids
 
o-RYE-o-nids
 
PUR-see-ids
 
kwa-DRAN-tids
 
south DEL-tah AK-wa-rids
 
south TOR-ids

Stars
 
 
Name
Pronunciation
 
AH-kuh-mar
 
AK-er-nar
 
A--krucks
 
ACK-you-benz
 
ad-HAR-a
 
al-KAP-rah
 
all-NAYR
 
all-NEE-yaht
 
all-soo-HAIL
 
al-BAL-dah
 
al-BEE-ri-oh
 
al-CHIH-ba
 
AL-kor
 
all-SYE--o-nee
 
al-DEB-ah ran
 
al-DER-a-min
 
al-da_FER-a
 
All-firk
 
all-JED-ee
 
al-JEN-nib
 
al-GEE-bah
 
al-GEEB-bah
 
AL-gall
 
ALL-gor-ab
 
al-HAY-nah
 
AL-lee-oth
 
AL-kade
 
al-ka-LOOR-ops
 
ALL-maaz
 
ALL-mahk
 
all-NAH-zul
 
ALL-nil-ahm
 
ALL-nit-ahk
 
AL-fard
 
al-FECK-ah, JEM-a
 
AL-fer-rats
 
all-RAH-kiss
 
all-RESH-ah
 
all-SHAIN
 
AL-tair
 
ALL-tays
 
al-TARF
 
al-TERF
 
 
al-UDE-rah
 
a-LOOL-ah ow-STRAH-liss
 
a-LOOLah bor-ee-AH-liss
 
ALL-zirr
 
UNG-ka
 
ANG-kah
 
an-TAIR-ease
 
arc-TOUR-russ
 
AR-kub
 
AR-kub
 
AR-kub PREE-or
 
AHR-neb
 
ah-SELL-a
 
ah-SELL-us ow-STRALICE
 
ah-SELL-us bore-ee-AL-is
 
ah-SELL-us
 
ah-SELL-us
 
ah-SELL-us
 
ass-mid-ISS-kee
 
ass-pid-ISS-kee
 
AH-tik
 
AT-las
 
AH-tree-a
 
 
AV-i-or
 
AH-za
 
ba-HAHM
 
BARN-ards star
 
BUT-en KYE-tos
 
BYED
 
BEL-la-trix
 
BET-el-jooz
 
boh-TAYN
 
can-OH-pus
 
kah-PELL-ah
 
KAF
 
CASS-ter
 
SEB-all-rye
 
ke-LAY-no
 
CHAH-ra
 
KERT-ahn,
 
core-ca-ROLE-ee
 
COOR-sah
 
DAH-bee
 
DEN-ebb
 
DEN-ebb al-JEE-dee
 
DEN-ebb
 
DEN-ebb
 
DEN-ebb KAY-tos
 
de-NEB-oh-la
 
DYE-a-dem
 
JOOB-a
 
DOOB-huh
 
ED-a-sick
 
e-LEK-tra
 
EL-noth
 
EL-ta-nin
 
EEN-if
 
er-RYE
 
e-RAHK-is (mu Draconis)
 
FO-mal-oh
 
fur-ROOD
 
GAK-kruks
 
JAW-sahr
 
JEEN-ah
 
GIRR-tahb
 
go-MAY-sah
 
GRAH-fi-us
 
GROOM-bridge
 
"
 
GROO-mi-um
 
HAH-dahr
 
HAM-al
Han
 
HAN
 
 
 
HEE-dus
 
HEE-dus
 
HOH-mahm
 
EYE-zar
 
JAB-bah
 
KAFF-al-JID-mah
 
KOWSS ow-STRAH-liss
 
KOWSS bor-ee-AH-liss
 
KOWSS me-RID-i-an-AL-is
 
KYED
 
kit-AL-fa
 
KOE-cab
 
core-ne-FOR-uss
 
 
KOOR-hah
 
la su-PURR-ba
 
la-KA-ya
 
la-KA-ya
 
la-LAHND
 
LAY-soth
 
MAH-ya
 
MAR-fick
 
MAR-kab
 
MAH-tahr
 
meb-SOO-tah
 
meg-REZ
 
MAY-sah
 
mek-BOO-dah
 
men-KAH-li-nan
 
men-KAHR
 
men-KENT
 
men-KIB
 
MER-ak
 
MER-o-pee
 
mess-AHR-tim
 
mee--a-PLASS-id-uss
 
mim-OH-sah, BAY-cruks
 
MIN-kar
 
MIN-ta-ka
 
MEE-ra
 
MIRR-ahk
 
MERE-fak
 
MERE-zam
 
MYE-zahr
 
MOOL-if-ayn
 
MOO-frid
 
MUSS-id-a
 
nar-AL-safe
 
NOWSS
 
nah-SHE-rah
 
NECK-ahr
 
nih-HALL
 
NOH-dus
 
NUN-kee
 
noo-SAH-kahn
 
Oaf-ih-YOU-kus
 
FEYE-et
 
FEK-da
 
ferk-AHD
 
PLAY-o-nee
 
poe-LAIR-is
 
POL-lucks
 
pour-EE-mah
 
PRO-see-on
 
PRO-puss, TAY-zhaht PRYE-or
 
RAH-sa-luss
 
rah-sell-GAYTH-ee
 
RAHS-al-haig
 
RAHS-al-MOTH-al-ah
 
REG-you-luss
 
RYE-jel
 
RYE-jel ken-TAW-russ
 
ROH-ta-nev
 
ROOK-baht
 
ROOK-baht
 
SAH-bik
 
sah-DUCK-be-ah
 
sah-dul-BAH-ree
 
sah-dul-MEL-ik
 
sah-dul-su-OOD
 
SADE-der
 
SAFE
 
SAHR-goss
 
SAHR-in
 
SHEE-at
 
SHED-er
 
SEG-in
 
seg-EEN-us
 
SHOWL-a
 
SHEL-ee-yak
 
SHARE-ah-tan
 
SEER-ee-us
 
SKAHT
 
SPEE-ka
 
STER-o-pee
 
swah-LOH-sin
 
soo-HALE-al-MOO-liff
 
SOOL-a-faht
 
SIRM-a
 
TAH-lith-a
 
THA-ni-ya ow-STRAH-liss
 
THA-ni-ya bor-ee-AH-liss
 
TAHR-ah-zed
 
TAY-get-a
 
teg-MEEN-e
 
TAY-zhaht pos-TER-i-o
 
THOO-bahn
 
tra-PEEZ-i-um
 
tra-PEEZ-i-um
 
tra-PEEZ-i-um
 
tra-PEEZ-i-um
 
uh-NOO-kul-lye
 
VEY-ga
 
vin-de-mee-AY-tricks
 
wah-SAHT
 
WUZ-un
Wei
 
 
WEZ-en
 
YED pos-TER-i-or
 
YED PRYE-or
 
zah-NYE-a
 
ZAW-rahk
 
zah-vee-JAH-vah
 
ZOSS-mah
 
zoo-BEN-el-AK-rab
 
zoo-BEN-el-je-NEW-bee
 
zoo-BEN-esh-ah-MAL-ee

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 Lure of Variable Stars

I’m a sucker for action. I love change. My favorite planet is Jupiter because of its rapid rotation, ever-changing moons, and volatile cloud features. I love watching Near Earth Asteroids and comets as they move across star fields. Recently I’ve become addicted to watching solar flares and prominences in rapid action with my solar telescope. But most of all, I love to observe variable stars.

All stars vary in brightness to some degree. Even our Sun, which seems so stable, changes its brightness as more or less of its surface is obscured by sunspots. But there are stars in the sky that undergo vast changes in brightness and color. Many are highly unpredictable in their behavior, and need years of study to uncover the mechanisms that drive them.

The Variable Zoo

The most famous are the novas and supernovas which suddenly shoot up from obscurity to prominence. Supernovas are relatively rare in our neighborhood. The last one was over 400 years ago in 1604. Novas are more common, several being observable in any given year.

Some stars appear to vary for purely mechanical reasons. These are called eclipsing binaries: two stars in a close orbit where one star eclipses the other, as regular as clockwork. Algol in the constellation of Perseus is a famous example of an eclipsing binary.

Other stars expand and contract slowly because of processes going on within them. The most common of these “pulsating variables” are long period variable stars like Mira in the constellation Cetus. Mira is larger in diameter than the orbit of Mars, and changes size, brightness, and color over a period of just under a year. It ranges over nearly six magnitudes in brightness, meaning that at its brightest, it is a hundred times brighter than when it’s at its dimmest. Another group of pulsating variables is called the Cepheids, named after the star Delta Cephei. These have much shorter periods than the Miras, ranging from 1 to 70 days, and their period is closely tied to their luminosity, which has led to their use as measuring sticks to determine the distance of globular clusters and galaxies.

Another group of variable stars is called “cataclysmic variables.” These include novas, supernovas, and the so-called “dwarf novas.” These last are the stars that interest me the most because they show the most action. My favorite is SS Cygni (TCY 3196-723-1), located close to the open cluster Messier 39. This star normally sits around twelfth magnitude, just visible in a small telescope, but every few weeks it shoots up unpredictably to about eighth magnitude. If you’re lucky enough to catch it in outburst, you can actually see it get visibly brighter. Stars like SS Cygni are actually close double stars consisting of a red dwarf and a white dwarf. The white dwarf is surrounded by a disk of gas stolen from the red dwarf which is drawn down into the white dwarf where it ignites, causing the sudden outburst in brightness.

 

Observing Variable Stars

Professional astronomers realized over a century ago that there were more variable stars in need of study than they could handle, so they enlisted the aid of amateur astronomers to monitor the brightness of a number of stars well suited to amateur observation: stars which changed in magnitude over a wide range and which took a long period to complete their cycle of brightness. For many years this work required no more than a telescope and a good set of charts, and such simple visual observations are still useful today, although nowadays amateurs have access to photoelectric photometers and CCD cameras which are capable of studying just about any star. The American Association of Variable Star Observers acts as a central clearing house for all sorts of amateur variable star observations, providing instruction, charts, and other support, and giving amateurs a simple online system for recording their observations.

Why observe variable stars? Mainly because it’s fun! You never know from night to night what you are going to find…remember what I said about action? No special equipment is needed other than a set of star charts which plot the variable star and give the brightness of non-variable stars around it, which are used to estimate the brightness of the variable.

If you are a deep sky observer, you already have one of essential skills of a variable star observer: you know how to locate objects in the sky. It doesn’t matter how you do it. I used traditional starhopping for several years, but now I use my Orion SkyQuest XT6’s IntelliScope setting circles to locate my variables. Once you’ve located the variable, you estimate its brightness as compared to other stars on the chart, and record the time of the observation. With a little practice you can make estimates to within a tenth of a magnitude. You can then log onto the AAVSO’s web site and enter your observation. Within ten minutes it will be moved into their database of over ten million observations, and you can see your observation on a light curve along with those of hundreds of other observers around the world. What could be neater?!

Unlike most of the observations amateur astronomers make, variable star observations have a serious side. By making a numerical estimate of the brightness of a star at a particular point in time, you are logging a piece of scientific data. The AAVSO maintains records online of every observation submitted to them over the past hundred years, keeping the records available to researchers around the world.

On a typical night, I’ll observe about a dozen stars from “my” list of about sixty stars visible at different times of year.

I keep finder charts along with the AAVSO charts in plastic sleeves in a loose-leaf binder, so that everything I need is close at hand. Since you never know ahead of time how bright a variable is going to be, you need to have a complete set of charts for each star; these can be downloaded from the AAVSO web site:

The biggest challenge in finding a variable star is that you’re looking for something that may be quite bright, or may be below the magnitude limit of your telescope, totally invisible to you. So what you look for is the star field, the pattern of stars surrounding the variable. Once you’ve found the field, you then check to see how bright the variable is. You then consult your AAVSO charts to see which stars are closest in brightness to the variable. Comparison stars on the charts are marked with their brightness to the nearest tenth of a magnitude. Because a decimal point might be confused with a faint star, they are left out, so that a 9.7 magnitude star is marked “97” and a 11.4 is marked “114” on the chart. You try to find a couple of stars, one slightly brighter than the variable, one slightly fainter, and then estimate where the variable falls between them.

Equipment for variable star observing

For visual observing as I have described above, the equipment needs are very simple. There are many variable stars within range of a pair of small binoculars, and some that can be observed with the naked eye alone. On the other hand, access to a large telescope lets you follow stars that become very faint at minimum.

I have found it advantageous to use eyepieces with a wide field of view, since they show me more of the sky at any given magnification, and let me see more comparison stars without having to move the telescope about.

My current strategy is to survey “my” variables using my Celestron 6" SCT telescope. I’ve programmed the controller with the coordinates of my variables, so I can quickly move through the list. Any variables which are currently too faint to be observable with the 6”, I revisit the next night with my larger 11” Dobsonian.

Where to start?

If you’re still not sure whether variable star observing is for you, I’d recommend reading Starlight Nights by Leslie Peltier (Sky Publishing). Peltier was the finest variable star observer of the 20th century, and his book is an entertaining introduction to a wonderful man and his love of the stars. It’s probably my very favorite astronomy book.

The AAVSO web site includes everything you need to get started. It has a complete observing manual, a list of good stars to start on, and all the charts you will need, all free of charge. Visit http://www.aavso.org

I’d recommend starting on stars that are easy to find and visible all year round, such as these stars in and around the Big Dipper:

A final warning though: variable star observing is highly addictive. Variable star observers probably spend more time at the eyepiece than any other amateur astronomers because, unlike deep sky or planetary observing, they are not dependent on dark skies or steady seeing. For years I carried out regular variable star observing every clear night from the middle of a large city, even when the Moon was full. The only thing that can stop you is clouds!

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. ​