Venus Vanishes Behind The Moon

Next Monday, December 7, the planet Venus will do a vanishing act behind the moon. 

In the course of its monthly journey around Earth, the moon often passes in front of stars, and occasionally planets.

Next Monday it will pass in front of the brightest of them all, the planet Venus, in what is called a lunar occultation.

This will be visible, weather permitting, all over North America. The only catch is that it occurs in broad daylight.

I’m often surprised that many people don’t know that the moon is visible in the daytime sky; in fact my son first spotted it when he was about 2 years old. That mainly says that very few people bother to look closely at the sky. On Monday, the moon will be a slender crescent only a few days away from new moon, so may be a bit harder to spot, though if you start observing at dawn you should have no trouble following it up into the blue sky.

Venus is also visible in daylight provided you know exactly where to look. On Monday, its closeness to the moon will help you spot it.

The time the occultation will occur depends on your exact location. For example, in New York City, Venus will disappear behind the moon at 12:43 p.m. EST and reappear at 1:51 pm. In Chicago the occultation lasts from 11:20 a.m. CST until 12:35 p.m. In Los Angeles, the times are 8:06 and 9:56 a.m. PST. The easiest way to get the exact times for your location is with a planetarium program like Starry Night or SkySafari.

It was observations of occultations by the moon of stars and planets that first told us that the moon has no significant atmosphere. Stars simply wink out and in as they pass behind the moon; planets show no fuzziness as they disappear behind the moon’s edge.

Starry Night gives you the opportunity to travel to other places in the universe, and view events from a different perspective. Our second image today shows the view of this occultation from the planet Venus at 12:35 p.m. EST. Instead of an occultation, we see what is called a transit, as one object (the moon) passes in front of another (Earth). The moon is moving from right to left in this view.

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Seen from Venus, the moon will transit Earth, blocking the view of most of North America. If the moon looks strange here, it’s because we’re looking at its far side, the side never seen from Earth. Credit: Starry Night software.

The occultation is already over on the east coast, to the right of the Moon, and has yet to begin on the west coast, to its left. The surface of the moon looks strange because we are seeing its “far side,” the side permanently turned away from Earth. This side has more mountains and craters and fewer open flat plains than the side we usually see.

The Moon At Its Best

One of the first things every new moon watcher learns is that, when observing the moon, timing is everything.

You might think that the best time to look at the moon with binoculars or a small telescope is when the moon is full, because it looks so big and bright. Well, that’s usually the worst time of the month for observing the moon. That’s because at full moon, the sun is high overhead on the moon’s surface, making it look like the desert at high noon. Far better times are at first and last quarters, when the sun is shining obliquely across the moon’s terrain, casting mountains and craters into high relief.

That’s what makes this week the perfect time to begin your exploration of our nearest neighbor in space. First quarter will be on Thursday night, November 19, meaning that the moon is one quarter of the way around the Earth in its monthly journey. The light will be hitting the terminator, the boundary between light and shadow, very obliquely, making the moon exactly half illuminated.

Because the moon is a world in its own right almost as large as the planet Mercury, and because it is so close to us, its surface geography is know almost as well as that of the Earth. Its surface has been mapped for hundreds of years, and most of its features have been named. Everyone who studies the moon soon becomes familiar with its major features and their names.

What catches everyone’s attention first at this phase of the moon is the three gigantic craters almost exactly in the centre of the moon. Like almost all the craters on the moon, these are named for famous astronomers of antiquity.

The northernmost and largest of the three is Ptolemaeus, named for Claudius Ptolemy. His name was given pride of place on the moon because he was probably the greatest astronomer of antiquity. His book, the Almagest, was written in the middle of the second century AD, and summarized all of astronomical knowledge of his time. It was written in Greek, but is known by its Arabic title because it only survived into the modern day in an Arabic translation.

The crater Ptolemaeus is 95 miles (153 km) in diameter, and is characterized by a wide flat floor pockmarked by many small craterlets.

The middle crater of these three is Alphonsus, named for Alphonso El Sabio, king of Castile in what is now Spain in the 13th century. Besides being a king, he was also an astronomer and a musician, and compiled the Alphonsine tables which were used to calculate planetary positions until the time of Kepler. This crater is a bit smaller than Ptolemaeus, but is more of a typical lunar crater with a central peak and complex system of rilles on its floor. This crater became famous in the 1950s when a Russian astronomer claimed to have seen a volcanic emission in it.

The third crater Arzachel is smaller still, 60 miles (97 km) in diameter, but with a larger central peak.

Just to the north of these three craters is the broad arc of the Apennine mountain range. This range is 370 miles (600 km) long and has peaks as high as 16,000 feet (5,000 m) in height. At its northern end is Mount Hadley, near which the astronauts of Apollo 15 landed in July 1971.

To the west of the Apennines is the broad expanse of the Mare Imbrium, the so-called “Sea of Rains.” Early astronomers had no idea how dry and airless the moon was, and its “seas” are dryer than the driest deserts on Earth. This is the second largest “mare” on the moon, exceeded only by the Oceanus Procellarum to its south.

The Mare Imbrium is a huge flat plain 720 miles (1160 km) across, with an area of 320,000 square miles (830,000 sq km). It contains many small mountain massifs and individual peaks. The lunar Alps are to its north, enclosing the beautiful crater Plato, 63 miles (101 km) in diameter. Its almost flat floor contains a number of small craterlets which are used by lunar astronomers to test the resolution of their telescopes. How many can you see?

Near the south pole of the moon, look for the gigantic crater Clavius, 140 miles (225 km) in diameter, and containing a whole series of craters in its interior graded in size. The largest of these is large enough to warrant a name of its own, Rutherford, 32 miles (51 km) in diameter.

With these landmarks learned, you can begin your exploration of the moon’s finer details. What I like to do myself is to start at the moon’s north pole and work my way down towards the southern highlands along the terminator, using a good lunar map to identify the topography.

Most of the features I’ve described can be seen with ordinary binoculars. Even the smallest telescope will reveal hundreds of smaller features. The moon is generally a good target for photography, because it is so bright that long exposures are not needed. You can even put your smartphone up to the eyepiece of your telescope and get remarkably good photos that way.

The Third of Four Eclipses In 2015 - September 13

The third of four eclipses in 2015 will occur this Sunday, September 13. It will be a partial eclipse of the sun, and unfortunately it will be visible only from southern Africa, the Indian Ocean, and parts of Antarctica.

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On Sunday morning, September 13, there will be a partial eclipse of the sun, visible in southern Africa, the Indian Ocean, and parts of Antarctica. Here it is seen from Cape Town, South Africa, where it will be at its maximum. Credit: Starry Night software.

The best view of this eclipse from an urban area will be from Cape Town, South Africa, where a maximum of 30 percent of the sun will be covered by the moon.

The eclipse begins in Cape Town just as the sun and moon are rising at 6:49 a.m. local time. Early risers will see a tiny bite out of the sun. It reaches its maximum at 7:43 a.m. By 8:50 a.m. the eclipse will be over.

This eclipse will be visible throughout South Africa, and also in southern parts of Madagascar, Mozambique, Zambia, and Zimbabwe. It will also be visible over a wide area of the Indian Ocean, and Antarctica (if you happen to be a penguin).

The best way to observe a partial solar eclipse is with a filter specifically designed for observing the sun, sold by stores specializing in telescopes. Safe “eclipse shades” are often widely available prior to an eclipse. A number 14 welder’s glass also works well, and is available from specialized welding shops. The ordinary number 12 welder’s glass sold in hardware stores does not provide adequate protection.

If you don’t have a proper solar filter, you can view the partially eclipsed sun with a pinhole camera by punching a hole about a millimeter in diameter in a piece of cardboard. Natural “pinholes” created by leaves on trees or reflections from a building’s windows will also work.

Under NO circumstances look directly at the sun, even with sunglasses, as you can quickly cause permanent damage to your eyes. If a small magnifying glass can light a fire in seconds, think what will happen to the retina of your eye by staring at the sun.

As always, we welcome your pictures of the partially eclipsed sun; a solar filter on your camera will be essential. The sensor in your camera is just as easily damaged by the direct sun as your eyes. Try to get a landmark or tree in the foreground to give a sense of scale.

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Sky Events For September 2015

Moon Phases

Saturday, September 5, 5:54 a.m. EDT

Last Quarter Moon

The Last Quarter Moon rises around 11:30 p.m. and sets around 3 p.m. It is most easily seen just after sunrise in the southern sky.

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Sunday, September 13, 2:41 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.

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Monday, September 21, 4:59 a.m. EDT

First Quarter Moon

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

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Sunday, September 27, 10:51 p.m. EDT

Full Moon

The September Full Moon is known as the Harvest Moon or Full Corn 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.

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Observing Highlights

Neptune at opposition

Tuesday, September 1, midnight

Neptune will be directly opposite the Sun in the sky, and visible all night. It is located in Aquarius but is too faint to be seen with the unaided eye. Use binoculars and a star chart from Starry Night.

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Mercury at greatest elongation east

Thursday and Friday, September 3 and 4, dusk

Mercury will be well placed in the evening sky for observers in the southern hemisphere, less so for observers in the north.

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Aldebaran and the Moon

Friday/Saturday, September 4/5, near midnight EDT

Observers on the eastern part of North America with low eastern horizons may be able to see the Moon occult the first magnitude star Aldebaran just after moonrise (around midnight, but check for local times). Observers in Europe will see it just before sunrise on the 5th.

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Zodiacal light

Friday, September 11–Thursday, September 24, before dawn

The best time in the year to see the dim glow of the zodiacal light in the pre-dawn eastern sky, the light reflected from millions of interplanetary particles. It lies along the ecliptic (shown in green).

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Partial solar eclipse

Sunday, September 13

This eclipse will be visible from southern Africa, Antarctica, and the oceans in between. Seen here is the maximum eclipse in Cape Town, South Africa.

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Equinox

Wednesday, September 23, 4:21 a.m. EDT

The Sun crosses the celestial equator moving southward, causing the days to grow shorter in the northern hemisphere and longer in the southern hemisphere.

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Lunar trio

Sunday, September 27, evening

There will be a triple treat for observers in eastern North America as sun, Earth, and moon align: a total lunar eclipse, the moon at its closest, and a full moon, all in one evening. At 8:12 p.m. EDT, the lunar eclipse will begin with the first faint lunar shadow creeping onto the moon. At 9:48, the moon reaches an extreme perigee, the closest it will get to Earth in all of 2015: 221,753 miles (356,877 km). Total phase of the eclipse will begin at 10:11 p.m. and mid eclipse will be at 10:47. At 10:51 it will be the instant of full moon, the largest full moon in 2015. At 11:23, the total phase of the eclipse will end, and at 1:23 a.m. the last of the moon’s shadow will leave the moon. In western North America, the moon will already be in eclipse when the moon rises. Observers in South America, Europe, and Africa will also see most of this eclipse. The illustration shows the moon just entering the umbral shadow of Earth at 9:12 p.m. EDT.

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Vesta at opposition

Monday, September 28, 11 p.m. EDT

The brightest asteroid Vesta will be directly opposite the Sun and visible all night in Cetus. At magnitude 6.2, it will be right at the limit of naked-eye visibility, but easily spotted with binoculars.

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Planets

Mercury is well placed in the evening twilight for the first half of the month. This apparition is more favorable for observers in the Southern Hemisphere.

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Venus is now a bright object in the pre-dawn sky, reaching maximum brightness of magnitude –4.8 on the 21st.

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Mars is low in the eastern twilight, moving eastward through Cancer into Leo.

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Jupiter reappears in the eastern pre-dawn sky in the middle of the month..

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Saturn is low in the southwest mid-evening sky, and sets in late evening.

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Uranus rises in mid-evening in Pisces, nearing opposition on October 12. 

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Neptune is in opposition on the 1st, visible all night in the constellation Aquarius.

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See The Supermoon On Saturday

You’ll probably be hearing a lot about a “super moon” for the next few months. This is not a term that astronomers use, but here are some facts about what will actually be happening.

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Full moon is when the sun, Earth, and moon line up with the Earth in the middle. As seen from the surface of the Earth, the moon is fully illuminated. Because it is exactly opposite the sun in the sky, the moon rises in the east just as the sun sets in the west and, roughly 12 hours later, sets in the west just as the sun is rising in the east.

Because the Earth is constantly revolving around the sun and the moon is constantly revolving around the Earth, full moon is an instantaneous event, occurring when the moon is exactly opposite the sun. This week this happens at 2:35 p.m. EDT on Saturday, August 29. 

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Full moon occurs this month at 2:35 p.m. EDT on Saturday, August 29. Credit: Starry Night software.

A minute earlier, the moon’s phase is “waxing gibbous,” and a minute later it is “waning gibbous.”

Each full moon occurs roughly 29.53 days after the previous full moon. “Roughly” because the moon’s orbit around the Earth is not a perfect circle, but instead is elliptical in shape. The exact time of full moon varies a little bit from month to month.

The most important result of the moon’s elliptical orbit is that sometimes the moon is closer to the Earth, and sometimes farther away. The time when it is nearest is called “perigee” and the time when it is farthest is called “apogee.”

What we are most interested in is perigee, the date and time when the moon is closest to Earth. This month perigee occurs on Sunday, August 30, at 11 a.m. EDT, about 18 hours after full moon. At that time, the moon will be 222,631 miles (358,290 km) away from Earth.

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The moon will be closest to the Earth, called “perigee,” the next morning at 11 a.m. Credit: Starry Night software.

Notice how less than a day’s change in position makes it clear that the moon is no longer full: you can see that it is lit more from the left side.

Events like full moon and perigee occur at exactly the same time when viewed from anywhere on Earth, even though the local time on the clock may look different. This month both full moon and perigee occur when it is daytime in North America, and the moon is below the horizon. The best time to see the full moon at perigee will be on Saturday evening, August 29. The moon will be a few hours past full, and perigee will be a few hours in the future, but that’s the closest we can get this month.

The important thing for astronomers is that the perigee distance is less than 360,000 kilometers. When the moon gets this close, its most important effect on the Earth, the ocean tides, gets stronger. On the day of perigee and the three days following, we will have larger tides than usual.

Looking ahead to next month, full moon will fall on Sunday, September 27 at 10:51 p.m. EDT, and perigee just 51 minutes earlier at 10 p.m. This perigee will be the closest in 2015, 221,753 miles (356,877 km). The result will be the largest full moon of the year, and even larger high tides. Notice that both events happen in the evening when the moon will be well placed in the sky.

The full moon of September is traditionally called the harvest moon, because it rises around sunset on several successive nights, giving farmers extra light in the evening to bring in their harvest.

The September full moon will also pass through the Earth’s shadow, a total eclipse of the moon, visible on the evening of September 27 in North and South America, and the morning of September 28 in Europe and Africa.

When the moon is close to full, we can see the strong contrast between its grey plains and white mountainous regions, which some people see as the “man in the moon” and others see as a rabbit.

With the naked eye or a small binocular, you can easily see the three main dark plains on the upper half of the moon, which bear the fanciful names of the Oceanus Procellarum (Ocean of Storms), Mare Serenitatis (Sea of Serenity), and Mare Imbrium (Sea of Rains). These were named before we knew that there were no open bodies of water on the moon, and no atmosphere to cause storms or rains. Look also for the brightest crater on the moon, Tycho, with its beautiful system of rays, cause by material expelled when it was caused by the impact of an asteroid millions of years ago.

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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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

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

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Saturn is well placed in Libra in the evening sky.

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Uranus rises in the late evening in Pisces. 

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

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Blue Moon Rises On Friday

On Friday, much of the world will have a “blue moon.”

The moon won’t actually be blue in color. The expression “once in a blue moon” is a statement about the rarity of an event, not about the moon’s color.

The expression “once in a blue moon” existed long before anyone tried to define exactly what a “blue moon” is. I believe that someone tried to come up with something about the moon that rarely happens, and got the idea that it might be an “extra” full moon in a given period of time.

In most years we have 12 full moons, one in each month. But because the lunar month is slightly shorter than the calendar month, some years, such as 2015, have 13 full moons. The synodic month (full moon to full moon) averages 29.530589 days, which is shorter than every calendar month in the year except February. Those extra 1/2 or 1-1/2 days accumulate over the year, causing the date of full moon to migrate through the calendar month.

To see what I mean, here is a list of full moon dates in 2015:

January 5
February 3
March 5
April 4
May 4
June 2
July 2
July 31
August 29
September 28
October 27
November 25
December 25

If we look forward to 2016, we see the date of full moon continuing to move forward through the month until it falls on the December 14 at the end of the year.

Full moon is an instantaneous event, when sun, Earth and moon fall close to a straight line. It occurs at the same instant everywhere in the world, whether the moon is above or below the horizon. The full moon on July 31 occurs at exactly 10:43 Coordinated Universal Time (UTC), the time that astronomers and pilots use. It is equivalent to Greenwich Mean Time (GMT), the local time in Greenwich, the suburb of London England where the Royal Observatory was established by King Charles II in 1675.

 Universal Time always uses the 24-hour clock, no “a.m.” or “p.m.” The day starts at midnight (0h), noon is 12h, and the last minute of the day begins at 23h 59m.

The time zones across the world are all measured from Greenwich and expressed in the number of hours they differ from Greenwich time. In most of eastern North America, we are currently on Eastern Daylight Time (EDT), which is obtained by subtracting 4 hours from GMT or UTC, so full moon occurs at 6:43 a.m. EDT.

As we move west across North America, we have to subtract more hours from UTC to get the local time. For example, on the west coast, we use Pacific Daylight Time, which subtracts 7 hours from UTC. Full moon occurs at 3:43 a.m. PDT.

So, where did the idea come from that this extra full moon should be called a “blue moon”? The idea seems to have originated in the Maine Farmers' Almanac, which started listing the quarter of the year in which 4 rather than 3 full moons occurred. In 1946, Sky & Telescope published an article which misinterpreted the older definition and defined a blue moon as the second full moon in a month. This definition was forgotten until the popular board game Trivial Pursuit used it as one of its trivia questions in 1986. This made this rather arcane definition mainstream.

So, when you look at the “blue moon” on Friday morning, don’t expect to see any different color. Just be aware that it is a byproduct of the many compromise we make so that our calendar works well most of the time. 

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.

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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.

Sky Events For May 2015

Moon Phases

Full Moon

Sunday, May 3, 11:42 p.m. EDT

The Full Moon of May is known as the “Milk Moon,” “Flower Moon,”  or “Corn Planting 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.

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Last Quarter Moon

Monday, May 11, 6:36 a.m. EDT

The Last Quarter Moon rises around 2 a.m. and sets around 1 p.m. It is most easily seen just after sunrise in the southern sky.

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New Moon

Sunday, May 18, 12:13 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.

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First Quarter Moon

Monday, May 25, 1:19 p.m. EDT

The First Quarter Moon rises around 1 p.m. and sets around 2:15 a.m. It dominates the evening sky.

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Observing Highlights

Mercury at greatest elongation

Thursday, May 7, evening twilight

This is the best evening apparition of Mercury this year for observers in the northern hemisphere. Use Venus to help you locate it. Mercury is most easily located by sweeping with binoculars, but once you’ve located it, you should be able to see it with your unaided eyes

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Uranus and the Moon

Friday, May 15, dawn

The Moon will pass just south of the Uranus just before sunrise.

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Double shadow transit on Jupiter

Wednesday, May 20, 8:06–8:35 p.m. EDT

The shadows of Io and Ganymede will be on opposite limbs of Jupiter, while the moons Io and Callisto will be central on the disk.

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Saturn at opposition

Friday, May 22, 10 p.m. EDT

Saturn will be in opposition to the Sun.

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Note how most of Saturn’s moons are in the same plane as the rings, except for Iapetus, whose orbit is tilted 8.3 degrees. At opposition, Iapetus is close to maximum elongation towards the west, while Tycho is close to maximum elongation towards the east.

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Double shadow transit on Jupiter

Wednesday, May 27, 10:01 p.m.–12:18 a.m. EDT

The shadow of Io chases the shadow of Ganymede across the face of Jupiter, catching up with it and passing it at 11:48 p.m. EDT. The Great Red Spot will also cross Jupiter’s disk during this period.

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Planets

 Mercury is well placed for northern hemisphere observers in the evening twilight sky for the first three weeks of May.

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Venus shines high in the western sky after sunset.

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Mars moves from Aries to Taurus on May 3, too close to the Sun to be visible.

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Jupiter is well placed in the evening sky all month.

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Saturn is just north of Scorpius’ “claws.” At opposition on May 22, it is visible all night.

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Uranus rises just before the Sun in Pisces.

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Neptune is in the eastern morning sky in the constellation Aquarius.

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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.