Sky at a Glance | February 1st, 2013

Comet PanSTARRS update. The incoming comet that we hoped would make a fine showing in March has been weakening. It may not even reach naked-eye visibility, what with its low altitude in evening twilight. See Comet PanSTARRS Punking Out?, and follow our continuing updates at SkyandTelescope.com/panstarrs.


Friday, February 1

  • The sky's biggest well-known asterism (informal star pattern) is the Winter Hexagon or Winter Circle. It fills the sky toward the east and south these evenings. Start with brilliant Sirius at its bottom. Going clockwise from there, march up through Procyon, then Pollux and Castor, then Menkalinen and Capella overhead, over and down to Aldebaran (with Jupiter blazing nearby!), down to Rigel, and back around to Sirius.

    Saturday, February 2

  • Your latitude makes a big difference in how the constellations appear. (Your longitude does not.) For instance, if you're as far north as 46° (roughly Portland, Minneapolis, Montreal, and central France), bright Capella passes straight through your zenith around 8 or 9 p.m. If you're as far south as 21° N (Guadalajara, Cuba, the mid-Sahara, and Kolkata), Jupiter currently crosses straight overhead in the evening.

    Wherever you are, Jupiter and Capella pass closest to your zenith exactly one hour apart. Jupiter goes first.

    Sunday, February 3

  • February is when Orion stands highest in the south in early evening. And this season, Orion is framed between the two brightest points in the sky: Jupiter high to its upper right and Sirius down to its lower left. Introduce them to someone!

    Monday, February 4

  • Jupiter's biggest moon, Ganymede, fades into eclipse by Jupiter's shadow around 7:35 p.m. EST. It reappears around 9:53 p.m. EST. Both events take place just east of the planet. Europa happens to be just south of Ganymede's reappearance point, by a bit less than a Jupiter diameter. When can you detect the first trace of Ganymede coming back?

    Later, Jupiter's Great Red Spot rotates across the planet's centerline at 11:25 p.m. EST.

    Tuesday, February 5

  • With the Moon gone from the evening sky, this week is a fine time to look for the zodiacal light from the Northern Hemisphere. At a clear, dark site with clean air, look west at the very end of twilight for a vague but huge, tall pyramid of pearly light. It's tilted left to align along the constellations of the zodiac — or more exactly, along the ecliptic line. So it points toward toward Jupiter.

    What you're seeing is sunlit interplanetary dust — comet and asteroid debris — orbiting the Sun near the plane of the solar system.

    Mars appears less than 1° upper left of much brighter Mercury low in the west-southwest after sunset on February 7th.
    Sky & Telescope diagram
    Mercury appears less than ½° upper right of much fainter Mars shortly after sunset on February 8th.
    Sky & Telescope diagram

    Wednesday, February 6

  • The cold northern wastes of the February sky may not have drawn your attention. But big, dim Camelopardalis, sprawling between Auriga and the north celestial pole, hosts some interesting wide double stars for binoculars. Take a tour with Gary Seronik's Binocular Highlight column and chart in the February Sky & Telescope, page 45.

    Thursday, February 7

  • Challenging Mercury-Mars conjunction. Look low in the west-southwest a half hour after sunset. Faint Mars is within 3/4° upper left of brighter Mercury (seen from North America), as shown here. Quite an interesting pair in binoculars! See our article Mercury Meets Mars.

    Friday, February 8

  • Conjunction continues. Mars is now within just 1/2° of Mercury low in the west-southwest in bright twilight (for North America) — a fine pair through a telescope, though both will be tiny and blurred. See Mercury Meets Mars.

    Saturday, February 9

  • Mars now appears 1.1° below brighter Mercury (for North America) low in the sunset glow. How much longer can you follow Mars, even with binoculars? Mars is finally ending an apparition that began more than a year and a half ago.


    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 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 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 with a telescope effectively.

    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 certainly not on mounts and tripods that are less than top-quality mechanically (able to point with better than 0.2° repeatability). As Terence Dickinson and Alan Dyer say in their invaluable 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

    Mercury and Mars, February 2013
    Mercury peaks in the early evening sky from February 11th to 21st, while much fainter Mars appears lower each evening. The two planets pass spectacularly close to each other on February 7th and 8th. Their disks are shown in their correct shapes and orientations, but their sizes are exaggerated hugely, roughly matching their appearance through a telescope at high magnification.
    Sky & Telescope diagram

    Mercury (magnitude –1.1) is emerging from the glow of sunset. On February 1st it's still very deep in bright twilight, but day by day it becomes higher and easier to see. Check for it each clear evening starting about 30 minutes after sunset, just above the west-southwest horizon. Bring binoculars.

    There too is fainter Mars. Mars is above Mercury until February 7th and 8th, when they pass less than 1° apart. After that Mercury is higher — coming into an excellent apparition of its own. See Mercury in February 2013.

    Venus (magnitude –3.9) is buried deep in the glow of sunrise.

    Mars (magnitude +1.2) is sinking deeper into the sunset. Brighter Mercury becomes your marker for finding it this week.

    Jupiter on Feb. 6, 2013
    The shadow of Ganymede was passing the Great Red Spot when Christopher Go took this image of Jupiter at 10:59 UT February 6th. South is up. Note the white outbreaks in the South Equatorial Belt downstream from the Great Red Spot.

    Jupiter (magnitude –2.5, in Taurus) dominates the high south in early evening, and the southwest later. To its left is orange Aldebaran; to its right are the Pleiades. The whole group sets around 2 or 3 a.m.

    In a telescope, Jupiter is shrinking (from 43 to 42 arcseconds wide this week) as Earth pulls farther ahead of it in our faster orbit around the Sun.

    Saturn (magnitude +0.5, in Libra) rises in the east-southeast around midnight or 1 a.m. local time. By the beginning of dawn it's at its highest in the south — more or less between Spica, far to its right, and Antares farther to its lower left. Saturn's rings are tilted 19° from edge on, the widest they've appeared in seven years.

    Saturn and moons on Jan. 26, 2013
    This extraordinary amateur image of Saturn was captured by Darryl Pfitzner Milika in Australia on January 26th. He used a 14-inch Celestron Schmidt-Cassegrain scope and an ASI120MM planetary video camera for frame-stacking. Just visible is the hexagonal shape of the storm that surrounds Saturn's north pole. The hexagon shape was first discovered by the Cassini spacecraft in 2007. South is up.


    Also visible in his image are four of Saturn's moons. From left: Dione, Enceladus, Mimas (!), and Tethys. Click for larger view.

    Darryl Pfitzner Milika

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    Uranus (magnitude 5.9, in Pisces) is getting low in the west after dusk.

    Neptune (magnitude 8.0) is lost in the sunset glow, in the background of Mercury and Mars.


    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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