Archive for April, 2014

The Sky This Week : April 22 – 29, 2014 !

The Sky This Week, 2014 April 22 – 29
Celebrate International Dark Sky Week!
Mars, 2014 April 22, 03:29 UT
Imaged with USNO’s 12-inch f/15 Clark/Saegmüller refractor

The Moon wanes through her crescent phases in the morning sky this week, wending her way through the rising autumnal constellations. New Moon occurs on the 29th at 2:14 am Eastern Daylight Time. You will find Luna in the company of bright Venus in the morning twilight of the 25th and 26th.

This week we celebrate International Dark Sky Week, dedicated to raising awareness of the importance and benefits of a dark nighttime environment. Begun in 2003 by a high-school student named Jennifer Barlow, it is now observed worldwide by an ever-increasing number of people and organizations. The practical benefits of better outdoor night lighting include better quality lighting for streets and business areas, less stray light reflecting up into the night sky, and tangible energy savings, both in costs and non-renewable resources. Recent studies have also shown that darker skies are beneficial to us, improving our sleep cycles and circadian rhythms, and hundreds of animal species benefit by reduced glare at both ground level and in the sky. Please visit the website of the International Dark Sky Association for more information on dark sky awareness and events occurring this week. The U.S. Naval Observatory is proud to be a lifetime sponsor of the IDA.

In conjunction with International Dark Sky Week, this week finds us in the middle of the “Globe At Night” citizen-science program April observing campaign. The absence of the Moon in the evening sky affords a great opportunity to see just how dark your favorite observing site is, and here is a way that you can report your findings for the betterment of science. April is a good month to do this since it’s fully dark by 9:30 pm and the haze and humidity of summer have yet to set in. Your objective is to locate the constellation of Leo, the Lion, which straddles the meridian high in the south at 10:00 pm. Count the number of stars you see in the constellation, then compare your observations to the charts on the Globe At Night website. It only takes a few minutes to do before turning in for the night, and each observation helps to chart the brightness of the night sky around the world.

Jupiter is still well-placed for observing in the western sky after sunset. He pops into view almost immediately after the Sun goes down and offers a fine telescopic target even in bright twilight. As darkness settles the giant planet dips lower toward the west, eventually setting just after 1:00 am. His apparent disc is now only about 2/3rds the size it was back at opposition in January, but a night with steady air should still reveal the planet’s dark equatorial cloud belts and four bright Galilean moons.

Mars As evening twilight ends ruddy Mars is well up in the southeastern sky. The red planet glows like a distant coal in the stars of Virgo, and contrasts nicely with the blue tint of the bright star Spica 11 degrees to the southeast. You’ll also probably notice that Mars is steadily closing in in on the second-magnitude star Porrima. By the end of the week the two objects will be about a degree and a half apart. Through the telescope Mars is putting his best face forward for North American observers; his most prominent dark albedo feature, the “Syrtis Major”, will face our Earthbound telescopes throughout the week.

Saturn follows Mars into the sky in the later stages of the evening. By midnight he’s well up in the southeast as he slowly wends his way westward among the stars of the obscure constellation of Libra, the Scales. Saturn doesn’t have the brazen red glimmer of Mars; he shines with a much more subdued yellow hue. However, once you’ve spent some time trying to glean detail from Mars’ diminutive disc, reward yourself with a view of the solar system’s most unusual world. Saturn will reach opposition in a few more weeks.

I was quite surprised to see Venus through my window this morning, ducking in and out of the clouds. My view is nearly due east, and for most of the current morning apparition the dazzling planet has been obscured by trees and houses from my sight. The planet is hugging the eastern horizon, but each passing day brings her a bit farther northward. She should be there to greet me for the next several months.


The Sky This Week : April 15 – 21, 2014 !

The Sky This Week, 2014 April 15 – 21
Missed the eclipse? Don’t worry, here’s three more chances.

Mars near opposition, 2014 April 13, 03:38 UT

The Moon wanes in the morning sky this week, diving down to the southern reaches of the ecliptic where she mingles with the rising summer constellations. Last Quarter occurs on the 22nd at 3:52 am Eastern Daylight Time. Luna passes just one degree south of Saturn in the pre-dawn hours of the 17th. On the following morning she will be about seven degrees north of the bright reddish star Antares. On the 20th she is well to the north of the “teapot” asterism formed by the brightest stars in the constellation of Sagittarius, the archer.

Most of us in the eastern U.S. got skunked by the weather for the total lunar eclipse, but reports from colleagues under clear skies reported it to be a very nice one with Luna glowing a gradient of hues ranging from brass to deep red. This was the first of a series of four total lunar eclipses that will all occur in sequence with no partial or penumbral eclipses in between. We’ll get a chance to see parts of all four between now and October of 2015. The next one will fall on the morning of October 8, 2014 beginning at around 5:15 am EDT when the Moon will be in the western sky. Totality begins at 6:24 am, with mid-eclipse occurring half an hour later. The Moon will then set as the Sun rises at 7:16 am. After that, mark April 4, 2015 on your calendar. The Moon will start to slip into the Earth’s shadow at 6:15 am EDT. Unfortunately Luna sets just 40 minutes later, so this eclipse will not be much of a show for the eastern part of the country. However, we like to save the best for last. On September 28, 2015 we’ll have a splendid eclipse that takes place in “prime time”, with the umbral phases lasting from 9:07 pm EDT until shortly after midnight. That’s the one I’ll be waiting for!

By the end of the week we’ll be starting the April observing campaign for the “Globe At Night” citizen-science program. To get ready for this use the evening skies this week to locate the constellation of Leo, the Lion, which is high on the meridian to the south at 10:00 pm. The main stars of Leo form two asterisms. The first is often called “The Sickle” and is anchored by the constellation’s brightest star Regulus. Moving upward from Regulus you’ll run into a beautiful gold-tinted star, Algieba. Binoculars show the color of this star very nicely, and a small telescope will split it into two close yellow components. Where The Sickle represents the Lion’s head, his hindquarters are formed by a small right triangle just to the east. Get to know these stars for the next few months; they will be the targets for star counts for Globe At Night.

Jupiter is now lowering in the western sky at the end of evening twilight. You should still have no trouble picking him out in the sky, but each successive night sends him creeping a little lower toward the horizon haze. He still sets well after midnight, but your window to get a good telescopic look at him while he’s still relatively high now ends at around 11:00 pm.

Mars is eager to take over for Jupiter as the evening’s “go-to” planet. His reddish tint is hard to miss in the eastern sky as the Sun sets, and by the late evening he’s high in the south, about 10 degrees northwest of the bright star Spica. The red planet slowly begins to recede from us, but his 15-arcsecond disc will reveal tantalizing surface features for owners of modest telescopes. Spend some time observing him and feel the presence of some of the world’s greatest astronomers of old, who tried to tease out the nature of the surface of this distant world from the far-flung shores of Earth.

You’ll find Saturn low in the southeast during the late night and early morning hours. His golden glow waits patiently for Mars to play out the brightest part of his apparition and crosses the meridian at around 2:30 am. In another month he’ll reach opposition, and you’ll have another target to keep you up late at the eyepiece.

You will still find bright Venus in the dawn twilight hugging the southeast horizon. The dazzling planet is slowly working her way northward along the ecliptic, and is currently passing through the dim autumnal constellation of Aquarius.

The Sky This Week : April 8 – 15, 2014 !

The Sky This Week, 2014 April 8 – 15
A busy Full Moon, and Mars at opposition.

Mars, imaged 2014 April 2

The bright region on the lower right limb is the north polar cap;
the bright spot to the lower left is formed by clouds
condensing around the summit of the massive
Olympus Mons volcano.

The Moon brightens the evening sky this week, passing through the springtime constellations as she waxes to the full phase. Full Moon occurs on the 15th at 3:42 am Eastern Daylight Time. April’s Full Moon is variously known as the Grass Moon, Egg Moon, Fish Moon, and Pink Moon. This last appellation will be particularly appropriate this year as Luna undergoes a total eclipse by the shadow of the Earth. More on this in a moment. This is also the Paschal Moon, since it’s the first Full Moon to follow the Vernal Equinox. It marks the beginning of the Jewish observance of Passover and sets the date for Easter among Christians. Look for Luna about five degrees south of the bright star Regulus on the evening of the 10th. On the 14th she passes between ruddy Mars and the blue-tinted star Spica, nudging just over a degree north of the star.

The last total lunar eclipse visible in its entirety from Washington occurred on December 21, 2010. We’ll get our next shot at one on the morning of April 15th. The Moon will enter the Earth’s penumbral shadow at 12:54 am EDT, marking the beginning of the event. Most of us probably won’t notice anything unusual until about 45 minutes later when Luna’s disc will begin to show a subtle darkening along her northwestern limb. At 1:58 am the transit through Earth’s umbral shadow begins, and over the next hour the Moon plunges ever deeper into it. At 3:07 am the total phase begins, with mid-eclipse occurring at 3:46 am. The total phase ends at 4:25 am, and Luna exits the shadow at 5:33. The final traces of the penumbral shadow clear the Moon’s face at 6:38 am, shortly after sunrise. As to what the Moon will look like during the total phase, that’s anybody’s guess. This is one of the things that makes watching these eclipses interesting. The darkness of the Moon’s disc depends very heavily on the clarity of the Earth’s atmosphere, so a bright, coppery-hued Moon means that the air over the Southern Hemisphere is clear. If you miss this one, don’t fret; we’ll get another eclipse (at a far more decent evening hour) on September 28, 2015.

The bright evening sky is still punctuated by the giant planet Jupiter, which can be seen high in the western sky as evening twilight fades into darkness. Old Jove still enjoys a prominent place in the sky, delighting earthbound stargazers until the midnight hour. Jupiter is always a treat to look at in the telescope, where you can see his four bright moons with almost any kind of optical aid. Each step up in aperture will reveal greater amounts of detail, especially if you patiently wait for moments of good “seeing” in our atmosphere. Try to locate the Great Red Spot as it transits the planet’s disc on the evening of the 10th.

Ruddy Mars is now at the peak of his current apparition. He reaches opposition on the 8th, when Earth passes between the red planet and the Sun. At this time he’ll rise at sunset and set at sunrise, remaining visible in the sky all night long. Earth and Mars are closest together on the 15th, when just over 57 million miles (92 million kilometers) separate us. This is the time to try to see details on his far-flung surface, views of which have tantalized earthbound astronomers for centuries.

Saturn now rises in the southeast at around 10:00 pm EDT. The ringed planet will continue to drift into the evening sky, and in another month will be dueling Mars for your attention. While Mars is much brighter, Saturn offers a most unearthly sight in the telescope as the planet spins across space surrounded by his icy rings

Venus continues to hug the southeast horizon in the gathering morning twilight. Although she is the brightest object in the sky after the Sun and Moon, her position makes her hard to spot unless you have a very good horizon to view her over.

The Sky This Week , April 1 – 8, 2014 !

The Sky This Week, 2014 April 1 – 8
Signs of summer in the night…

The last of winter’s stars

Paris, Virginia, 2014 March 27

The Moon returns to the evening sky this week, springing upward from the western horizon as she waxes through her crescent phases. First Quarter occurs on the 7th at 4:31 am Eastern daylight Time. This is a good week to explore our nearest neighbor as she goes through her crescent phases. Her high declination gives her a lofty perch on successive nights, showing her to good advantage. Look for her just four degrees west of the bright star Aldebaran on the evening of the 3rd. On the 6th she passes just over five degrees south of bright Jupiter.

As April opens we can still find the bright stars of the Great Winter Circle lingering in the west and southwestern skies as dusk deepens to darkness. This is the last month we’ll have to see these bright patterns in a dark evening sky until late this fall. The way this past winter has been, I, for one, won’t be sad to see them go. As much as I enjoy looking at Orion striding over a cold, snowy landscape, it’s time for him and his friends to give way to stars of warmer times. Orion’s most striking naked-eye feature to me has always been the ruddy glowing coal of the star Betelgeuse, which marks the Hunter’s shoulder. Betelgeuse now sets just before midnight, but if you look to the southeastern sky at this time you’ll see another glowing coal rising out of the haze. This is the star Antares, brightest star in the summer constellation of Scorpius. Both Betelgeuse and Antares are “red supergiants”, stars which are near the end of their evolutionary tracks. They are swollen hulks of massive stars whose tenuous outer envelopes would gobble up the planets in our solar system out to the orbit of Mars. They have enormous but relatively cool surfaces, hence their distinct ruddy hue. In mythology the lowly scorpion was the one creature that Orion couldn’t overcome, so the gods placed the two adversaries on opposite sides of the sky. There are a number of other similarities between the stars of these two constellations, but we’ll save those for another time.

You still have a few hours of darkness to enjoy the view of Jupiter in the evening sky. The giant planet becomes visible near the meridian almost as soon as the Sun sets and dominates the western sky once it’s fully dark. You’ll have a good view of him until the wee hours with the naked eye, but if you’re using a telescope to peruse him he’ll start to settle into more turbulent air by midnight. His disc has diminished by almost 10 arcseconds in apparent diameter since opposition back in January, but he still offers the most generous surface to look at of all the planets. His atmosphere remains in constant turmoil; on the last night of March I spotted a large feature that wasn’t there a week ago. It must be a ferocious storm, because it is about as long as the circumference of the Earth!

Mars is quickly moving into the evening sky and is currently at his best and brightest for the current apparition. Opposition occurs on the 8th when the red planet rises at sunset and sets at sunrise. At this time his telescopic disc will be just over 15 arcseconds in apparent diameter, less than half that of Jupiter. Nonetheless, careful scrutiny of Mars through a telescope will reveal tantalizing bits of detail to the patient observer. The planet’s shrinking north polar cap and transient clouds over its high volcanic peaks have been very prominent of late.

Saturn will reach opposition in early May and is following on Mars’ heels. Even though he’s quite low in the sky his mysterious rings are tipped very favorably in our direction. Almost any telescope should show them. The ringed planet is a fine reward for observers who spend a few hours trying to tease detail from the ruddy disc of Mars.

Venus greets early risers in the southeast during morning twilight. There is no mistaking this dazzling world, but you’ll need a clear horizon to get a good look at her.