Sky at a Glance | March 2nd, 2012

Evening twilight view
Jupiter and Venus continue drawing together by nearly 1° per day. On March 2nd they're still 10° apart.

Friday, March 2

  • Bright Venus and Jupiter continue to draw closer together in the evening sky this week. And use them to find little Mercury far below. Watch Mercury fading day by day.

  • The dark edge of the Moon occults (covers) the 4.1-magnitude star Nu Geminorum late tonight for most of eastern and central North America. With a telescope, watch the star creep up to the Moon's limb and then suddenly wink out. Some times: Montreal, 12:15 a.m. EST; Washington DC, 12:29 a.m. EST; Atlanta, 12:49 a.m. EST; Chicago, 11:21 p.m. CST; Kansas City, 11:34 p.m. CST, Edmonton, 9:32 p.m. MST. More times.

    Saturday, March 3

  • The Moon shines above Procyon after dark. Upper left of the Moon are Pollux and Castor.

  • Mars is at opposition, appearing opposite the Sun in Earth's sky. This is the most distant opposition of Mars in its 15-year cycle of oppositions near and far, so the planet appears only 13.9 arcseconds wide. At its next time around in April 2014, Mars will reach a diameter of 15.2″.

    Sunday, March 4

  • Mercury is at greatest elongation, 18° east of the Sun. Look for it above the sunset horizon far below and perhaps a bit right of Venus and Jupiter. Mercury remains at nearly the same place above your horizon each evening this week, but it's fading day by day.

    Evening twilight view to the east
    Watch the big bright Moon pass Regulus and Mars opposite the Sun.

    Monday, March 5

  • Mars is at its closest to Earth for this apparition: 100.8 million km (62.6 million miles). Mars appears 13.9 arcseconds wide, compared to the 24″ or 25″ it reaches during its closet swing-bys. The last time that happened was in 2003; the next will be in 2018.

  • The eclipsing variable star Algol should be at minimum light, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 9:25 p.m. EST. It takes several additional hours to fade and to rebrighten.

    Tuesday, March 6

  • The nearly full Moon hangs to the right of Regulus this evening, as shown here. Mars shines to their lower left.

    Wednesday, March 7

  • Mars shines left of the full Moon this evening, as shown here; both are at or near opposition. (The Moon is exactly full at 4:39 a.m. Thursday morning EST.)

    Thursday, March 8

  • This is the time of year when Sirius, the brightest star after the Sun, shines due south at nightfall. Upper left of it (by two fists at arm's length) is Procyon. Upper right of Sirius by the same distance is Betelgeuse in Orion's shoulder. These three stars form the bright, colorful Winter Triangle.

    Friday, March 9

  • The Big Dipper glitters high in the northeast these evenings, standing on its handle. You probably know that the two stars forming the front of the Dipper's bowl (currently on top) are the Pointers; they point to Polaris, currently to their left.

    And, you may know that if you follow the curve of the Dipper's handle out and around by a little more than a Dipper length, you'll arc to Arcturus (now rising in the east).

    But did you know that if you follow the Pointers backward the opposite way, you'll land in Leo?

    Draw a line diagonally across the Dipper's bowl from where the handle is attached, continue on, and you'll go to Gemini.

    And look at the two stars forming the open top of the Dipper's bowl. Follow this line past the bowl's lip far across the sky, and you crash into Capella.

    Saturday, March 10

  • The waning gibbous Moon forms a nice triangle with Saturn and Spica once they're well up by 10 or 11 p.m.

  • Daylight-saving time begins (for most of North America) at 2 a.m. Sunday morning. Clocks spring forward 1 hour.


    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 map in the center of each issue of Sky & Telescope, the essential magazine of 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 that's less than one star in an entire telescopic field of view, on average. By comparison, Sky Atlas 2000.0 plots 81,312 stars to magnitude 8.5, typically one or two stars per telescopic field. Both atlases include many hundreds of deep-sky targets — galaxies, star clusters, and nebulae — to hunt among the stars.
    Sky & Telescope

    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 the even larger Uranometria 2000.0 (stars to magnitude 9.75). And read how to use sky charts effectively.

    You'll also want a good deep-sky guidebook, such as Sue French's new 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 classic if dated Burnham's Celestial Handbook.

    Can a computerized telescope replace charts? I don't think so — not for beginners, anyway, and especially not on mounts and tripods are less than top-quality mechanically (able to point with better than 0.3° repeatability). 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

    Jupiter at 10:31 UT February 27, 2012
    The Great Red Spot was about to rotate off Jupiter's visible disk when Christopher Go in the Philippines took this image on February 27th local time. South is up.

    Mercury (about magnitude –0.8) is having its best evening apparition of 2012. As the afterglow of sunset fades in the west, look near the horizon for Mercury far below and perhaps a bit right of bright Venus and Jupiter.

    Venus and Jupiter (magnitudes –4.3 and –2.2) are the two bright “Evening Stars” shining in the southwest to west during and after dusk. Venus is the brighter, lower one. Watch Jupiter closing in on it by about 1° every day! The gap between them narrows this week from 10° to just 4°. These are the two brightest celestial objects after the Sun and Moon. To Jupiter's right are the stars of Aries.

    In a telescope, Venus is a brilliant white gibbous disk 19 arcseconds tall and 62% sunlit. Jupiter shows a much lower surface brightness, being farther from the Sun, but its apparent diameter is almost twice as great: 36 arcseconds.

    Mars on March 5-6, 2012
    Syrtis Major is almost dead center in this Mars image taken by S&T's Sean Walker on the night of March 5–6. Mars was 13.9 arcseconds wide. He used a 12.5-inch reflector and stacked-video imaging. Don't expect views this good visually!


    South is up, and celestial east is to the right (the preceding side; Mars's morning side). Notice the bright cloud over Elysium at the 8 o'clock position here, and the edge of the North Polar Cloud Hood over Hellas at top. The North Polar Cap (NPC) has been shrinking in the Martian northern-hemisphere spring, exposing the dark collar around it. Just left of the cap, writes Walker, notice a yellowish apparent dust event.

    S&T: Sean Walker

    Mars (magnitude –1.2, in Leo) is at opposition March 3rd and nearest Earth on March 5th. It shines bright fire-orange low in the east during twilight and dominates the eastern sky after dark. Regulus twinkles about 12° to its upper right. Mars shines highest in the south, in the sharpest telescopic view, around midnight.

    In a telescope Mars is 13.9 arcseconds wide, the largest it will appear until 2014. See our Mars map and observing guide in the April Sky & Telescope, page 50, or the shortened version online.

    Saturn (magnitude +0.4, in Virgo) rises in the east around 9 or 10 p.m. and shines highest in the south around 3 a.m. Accompanying it is Spica, 7° to Saturn's right or upper right and a little fainter at magnitude +1.0. In a telescope Saturn's rings are tilted 15° from our line of sight, their most open since 2007.

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

    Saturn on Jan. 21, 2012
    Saturn's rings are tipped a good 15° from our line of sight. South is up. Note the very pale light band in the north temperate region, the remnant of the dramatic, billowing white outbreak that attracted so much attention last year. Christopher Go took this image on January 21, 2012.

    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 Standard Time (EST) equals Universal Time (also known as UT, UTC, or GMT) minus 5 hours.


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