Sky at a Glance | April 11th, 2008

By: Alan MacRobert April 11, 2008 0

Some daily events in the changing sky for April 11– 19.

The waxing Moon is crossing Gemini, where it passes Mars. These diagrams are exact for the middle of North America (longitude 90° west, latitude 40° north). European observers: move each Moon symbol a quarter of the way toward the one for the previous date.

Sky & Telescope diagram.

Friday, April 11

Tonight the Moon (nearly first-quarter) passes very near Mars in Gemini.

Saturday, April 12

First-quarter Moon (exact at 2:32 p.m. EDT). The Moon lines up to the left of Castor and Pollux this evening, as shown here.

Sunday, April 13

On April evenings the Big Dipper curls around upside down very high in the north-northeast, as if dumping its contents into the Little Dipper, which is curling upward far below the Big Dipper's bowl as if to play catch. The Little Dipper is much dimmer and harder to make out.

Monday, April 14

The Moon shines to the right of Saturn and Regulus this evening, as shown below.

Even through the glare of Earth's Moon nearby, a telescope will show Saturn's even bigger moon Titan, 3,400 times farther away. Saturn and Titan are 72 light-minutes distant, compared to the Moon's 1.3 light-seconds. Tonight Titan appears four ring-lengths to Saturn's west.

Tuesday, April 15

The thickening Moon is lower left of Saturn and Regulus in early evening, as shown below, and directly left of them by midnight.

Wednesday, April 16

Even with spring well under way (in the Northern Hemisphere), bright Sirius, the "Winter Star," is still sparkling in the southwest after dark. And the winter constellation Orion is off to its right. How late into the warming season can you keep them in view at dusk?

Fifth-magnitude asteroid occultation? Late tonight the 4.8-magnitude star 22 Scorpii, just north of Antares, will be blacked out for up to 1.7 seconds by the small, faint asteroid (5508) 1988 EB. The path is uncertain; it could happen along a track pretty much anywhere across the Midwest, Great Lakes region, Mid-Atlantic states, and the Northeast. The occultation should happen around 1:54 a.m. Thursday morning Eastern Daylight Time at the Atlantic coast, and 12:58 a.m. CDT in the Upper Midwest. The star will be low in the southeastern sky. See our article, and the map and details on Steve Preston's asteroid occultation site.

Thursday, April 17

If you've got a clear view of the northeast horizon, you're ideally sited to watch the slow rise of Vega, the bright "Summer Star." In mid-April Vega clears the horizon around 9 or 10 p.m. daylight saving time (depending on where you live in your time zone). How early can you see it?

Friday, April 18

Look lower left of the bright Moon this evening for Spica. Look lower right of the Moon for the four-star pattern of Corvus, the Crow. The bright star shining far off to the Moon's left, in the east, is ginger-ale-colored Arcturus.

Saturday, April 19

Full Moon tonight (exact at 6:25 a.m. Sunday morning Eastern Daylight Time.) Look above the Moon for Spica.

For skywatchers in the longitudes of North America, the waxing gibbous Moon passes Saturn and Regulus about halfway between the evenings of April 14th and 15th: in other words, at the time of early evening in the longitudes of China, Korea,and Japan (where the local date will be the evening of the 15th).

Sky & Telescope diagram

Want to become a better amateur astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope. For an easy-to-use constellation guide covering the whole evening sky, use the big monthly foldout map in each issue of Sky & Telescope, the essential magazine of astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).

Once you get a telescope, to put it to good use you'll need a detailed, large-scale sky atlas (set of maps; the standards are Sky Atlas 2000.0 or the smaller Pocket Sky Atlas) and good deep-sky guidebooks (such as Sky Atlas 2000.0 Companion by Strong and Sinnott, the even more detailed Night Sky Observer's Guide by Kepple and Sanner, or the enchanting though increasingly dated Burnham's Celestial Handbook). Read how to use them effectively.

More beginners' tips: "How to Start Right in Astronomy".

This Week's Planet Roundup

Jupiter is getting high enough now in early dawn to show detail well in a telescope . The North Equatorial Belt (brown band just above center) remains wide and very dark. The South Equatorial Belt (just below center) has divided into northern and southern halves. A South Equatorial Belt Disturbance has created the irregular white markings near the left (following) limb. Note the very different colors of the belts in the in the northern and southern hemispheres. The Equatorial Zone, after being remarkably dark last year, has returned to its normal bright state. Christopher Go took this extremely sharp image on April 3, 2008. The time was 20:20 UT, and the System II central-meridian longitude was 32°. North is up (but remember that many telescopes will show south up).

Christopher Go

Mercury is lost in the glare of the Sun.

So is Venus. . . or is it? How low does bright Venus (magnitude –3.8) really have to go before it disappears? We want your observations; see our article.

Mars (magnitude +1.0, in the center of Gemini) shines high in the southwest to west during evening. It forms a longish, skewed triangle with Castor and Pollux above it. In a telescope Mars is only 6.3 arcseconds wide now — a tiny gibbous blob.

Jupiter (magnitude –2.3, in eastern Sagittarius) glares in the southeast before and during dawn. The farther south you live, the higher you'll be able to observe it before dawn gets too bright.

Saturn (magnitude +0.4, near Regulus in Leo) glows high in the southeast to south during evening. Fainter Regulus (magnitude +1.4) is about 2½° from Saturn: to its right at dusk, and lower right of it later at night. They'll appear closest (2¼° apart) the first week in May.

The two form a long, narrow triangle with Gamma (γ) Leonis, which at magnitude +2.1 is only a little dimmer than Regulus. It's located 8° to Saturn's north.

Saturn with four of its satellites, shot on the evening of March 25th. Orange Titan is at top, Rhea is at top right, Dione is directly to Saturn's right, and Tethys is just to the planet's lower left. North is up. Scott Hammonds took the raw video frames in Florida using a Meade 10-inch Schmidt-Cassegrain telescope and a DMK 21AU04.AS camera; processing by Sean Walker.

Scott Hammonds and Sean Walker

Telescope users: there's more to Saturn than you may realize. See our Saturn observing guide in the April Sky & Telescope, page 66.

Uranus and Neptune are still low before dawn.

Pluto (magnitude 14.0, in northwestern Sagittarius) is highest in the south just before dawn's first light.

All descriptions that relate to your horizon or zenith — 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) equals Universal Time (UT, UTC, or GMT) minus 4 hours.

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About Alan MacRobert

Alan M. MacRobert became an avid Sky & Telescope subscriber in 1966 at age 14, joined the editorial staff in 1982, and is now a senior contributing editor, semi-retired. He played a role in practically every part of the magazine and the company's other products for more than a generation, both on the amateur-observing side and the science-reporting side. In 1994 a book collection of his observing how-tos and telescopic sky tours was published as Star Hopping for Backyard Astronomers. He has produced This Week's Sky at a Glance online every week since 1989.