This Week’s Sky at a Glance, March 20 – 28

Some daily sky sights among the ever-changing Moon, planets, and stars.

Nova in Sagittarius reaches magnitude 4.3, then fades. [Updated March 25th.] A classical nova that leaped up to 6th magnitude on March 15th in the Sagittarius Teapot continued to brighten to about magnitude 4.3 as of March 21–22, then faded to about 5.9 as of the 25th. Sagittarius is low in the south-southeast before the first light of dawn (as seen from mid-northern latitudes). Article, charts: Nova Sagittarii: Catch It While You Still Can.

Friday, March 20

The Sun underwent a total eclipse for parts of the North Atlantic and Arctic Ocean early today. The partial phases swept across all of Europe, North Africa, and central Asia. Lots of news coverage.

As dusk turns to night, spot Venus still shining in the west. To its upper right by about a fist at arm's length, look for 2.0-magnitude Hamal, the brightest star of Aries. Farther to Venus's upper left or left, look for 2.5-magnitude Menkar, Alpha Ceti.

Spring begins in the Northern Hemisphere at the equinox, 6:45 p.m. EDT (3:45 p.m. PDT). This is when the Sun crosses the equator heading north for the season.

Moon, Mars and Venus March 21, 22 and 23, 2015

Watch the young waxing crescent Moon pass faint Mars and bright Venus in twilight. The Moon is drawn three times its actual apparent size.

Saturday, March 21

In twilight, look west well below Venus for a very thin waxing crescent Moon close to Mars, as shown here. The Moon is just one day old; new Moon was marked by yesterday's solar eclipse.

We see the Moon's night side (dimly earthlit), and just a little of the sunlit side around the edge, because the Moon is still nearly along our line of sight to the Sun. Faraway Mars shows us mostly its day side, because it's nearly on the same line of sight on the far side of the Sun.

Sunday, March 22

Crescent Moon and Venus. Look west in twilight for the waxing crescent now posing with Venus, as shown here. At the times of twilight for North America, Venus is 3° or 4° to the Moon's right. Although they look close together, Venus is currently 520 times farther away.

Monday, March 23

Venus shines well to the Moon's lower right this evening.

Venus is brightest point of light at dusk. The second-brightest is Jupiter much higher in the southeast. Look to the right of Jupiter by two or three fists at arm's length for Procyon; look the same distance lower right from Procyon — and there's the evening's third-brightest point, Sirius.

Tuesday, March 24

The Moon shines amid the big, loose Hyades cluster for the Americas. The Moon occults Aldebaran for Alaska and northwestern Canada. See map and timetables of Aldebaran's disappearance and reappearance.

Wednesday, March 25

Look well to the left of the Moon this evening for Betelgeuse in the top of declining Orion. Look lower right of the Moon for similarly-colored Aldebaran, not quite as bright, in Taurus.

Thursday, March 26

The first-quarter Moon shines above Orion and below Gemini this evening. If you have a dark enough sky (or binoculars), you can see that the Moon is in or near Orion's dim, upraised club.

Friday, March 27

This evening the Moon forms a big kite shape with bright Jupiter far to its left, Pollux to the Moon's upper left, and Procyon to its lower left.

Saturday, March 28

Now the Moon shines inside the triangle of Jupiter, Pollux, and Procyon.

Want to become a better astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.

This is an outdoor nature hobby; for an easy-to-use constellation guide covering the whole evening sky, use the big monthly map in the center of each issue of Sky & Telescope, the essential guide to astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).

Pocket Sky Atlas

The Pocket Sky Atlas plots 30,796 stars to magnitude 7.6 — which may sound like a lot, but it's still less than one per square degree on the sky. Also plotted are many hundreds of telescopic galaxies, star clusters, and nebulae.

Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of charts). The standards are the little Pocket Sky Atlas, which shows stars to magnitude 7.6; the larger and deeper Sky Atlas 2000.0 (stars to magnitude 8.5); and once you know your way around, the even larger Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts with a telescope.

You'll also want a good deep-sky guidebook, such as Sue French's Deep-Sky Wonders collection (which includes its own charts), Sky Atlas 2000.0 Companion by Strong and Sinnott, the bigger Night Sky Observer's Guide by Kepple and Sanner, or the beloved if dated Burnham's Celestial Handbook.

Can a computerized telescope replace charts? Not for beginners, I don't think, and not on mounts and tripods that are less than top-quality mechanically (able to point with better than 0.2° repeatability, which means fairly heavy and expensive). As Terence Dickinson and Alan Dyer say in their Backyard Astronomer's Guide, "A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand."

This Week's Planet Roundup

On March 23rd Christopher Go made this remarkable animation of bright-orange Io and darker Callisto passing each other in opposite directions. Both are very well resolved into disks. The image contrast appears enhanced just a bit; in reality there's an 0.7-magnitude (2-times) difference in the total brightnesses of Io and Callisto, and a 3.7-times difference in their albedos or average surface brightnesses. North is up. Full-size animation.

Mercury is hidden deep in the glow of sunrise.

Venus (magnitude –4.0) blazes in the west during and after evening twilight as the unmistakable "Evening Star."

Mars is magnitude +1.3, less than 1% as bright as Venus. It's gradually sinking ever farther below or lower right of Venus — from 12° below it on March 20th to 15° below on the 27th.

Jupiter on March 17, 2015

On March 17th, two white outbreaks dominated the turbulent wake of the Great Red Spot on its following (celestial eastern) side (to the right here); since then the area has become more chaotic. The Red Spot Hollow was wide and light-colored. Far below, in the narrow, broken North Temperate Belt, the thin, dark red barge had become more elongated than before. South is up. This image, by Christopher Go, has been sharpened and contrast-boosted compared to the one above.

Jupiter (magnitude –2.4, in Cancer) shines high in the southeast as the stars come out. It's the brightest point of light on that side of the sky. It passes highest in the south around 10 p.m. daylight-saving time.

In a telescope Jupiter is still 43 or 42 arcseconds wide. Don't expect to see nearly the amount of detail with your eye that sophisticated video-frame stacking with a large amateur telescope can bring out, such as in the fine image here!

Saturn (magnitude +0.3, at the head of Scorpius) rises around midnight daylight-saving time. It's highest in the south just before dawn begins. Below or lower left of Saturn by 8° is orange Antares, the Scorpion's heart.

Look just ½° below Saturn before dawn for Nu Scorpii, a showpiece double star for telescopes. And less than 2° to their right is Beta Scorpii, an even finer telescopic double.

Uranus and Neptune are hidden behind the glare of the Sun.

All descriptions that relate to your horizon — including the words up, down, right, and left — are written for the world's mid-northern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America.

Eastern Daylight Time (EDT) is Universal Time (UT, UTC, or GMT) minus 4 hours.

“This adventure is made possible by generations of searchers strictly adhering to a simple set of rules. Test ideas by experiments and observations. Build on those ideas that pass the test. Reject the ones that fail. Follow the evidence wherever it leads, and question everything. Accept these terms, and the cosmos is yours.”

— Neil deGrasse Tyson, 2014.

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