Sky at a Glance | February 22nd, 2008

Some daily events in the changing sky for February 22 – March 1.

Mercury is close to Venus all this week (and all March too), but they're closest Wednesday morning. Make it a project! Find a spot with a good view low to the east-southeast and bring binoculars.
Sky & Telescope diagram
Friday, February 22

  • High overhead these evenings, notice how similar the pairing of Mars and Beta Tauri looks to the pairing of Pollux and Castor farther east. Even their colors are alike: orange and blue-white in both cases.

    Compare also with the pairing of Procyon and Beta Canis Minoris lower down — and the pairing of Sirius and Beta Canis Majoris lower still. With fresh eyes, there's no end to the new sky patterns you may notice.

    Saturday, February 23

  • Saturn is at opposition tonight, opposite the Sun in our sky. This means it rises around sunset, is highest in the south around midnight, and sets around sunrise. With a telescope look for the Seeliger effect, described in the "Saturn" section below.

    Sunday, February 24

  • The bright eclipsing variable star Algol should be in one of its periodic dimmings, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 9:51 p.m. Eastern Standard Time. Algol takes several additional hours to fade and to rebrighten.

    Monday, February 25

  • With the Moon gone from the early-evening sky for the next two weeks, look for the zodiacal light as twilight fades away. You'll need a clean, unpolluted sky. The zodiacal light is a huge, narrow, tilted pyramid of pearly glow extending up from the western horizon and running along the constellations of the zodiac. What you're seeing is interplanetary dust in the plane of the solar system, lit by sunlight.

    This is the best season of the year for seeing the evening zodiacal light if you're in the Northern Hemisphere — because this is when the ecliptic extends most nearly upright from the western horizon at dusk.

    Tuesday, February 26

  • Venus and Mercury appear closest together Wednesday morning. As dawn brightens, use binoculars to spot Mercury just 1.2° above bright Venus very low over the east-southeast horizon; see the illustration at the top of this page. Best time to look: about 45 to 30 minutes before sunrise. To find your local sunrise time (and much else), make sure you've put your location and time zone into our online almanac (and make sure the Daylight Saving Time box is unchecked).

    Wednesday, February 27

  • Algol should be at minimum light for a couple hours centered on 6:40 p.m. EST.

  • The red long-period variable star S Canis Minoris, not far from Procyon, should be at maximum light (7th or 8th magnitude) around now.

    Thursday, February 28

  • Last-quarter Moon (exact at 9:18 p.m. EST).

    Friday, February 29

  • Just after nightfall this week, Orion stands perfectly erect with his two feet-stars (Rigel and Saiph) perfectly level. High above him glows little Mars. Off to his left, by about two fist-widths at arm's length, is Procyon, the Little Dog Star, following behind him as he crosses the sky. Lower left of Orion by a similar distance is brighter Sirius, the Big Dog Star, following behind as well.

    Saturday, March 1

  • As twilight fades and the stars come out, look straight overhead for bright Capella. If you happen to live at latitude 46° north (the Oregon-Washington border, Montreal, central Maine, central France), Capella passes exactly over your head once a day. If you're south of there, Capella passes 1° north of your zenith for every degree you're south of that latitude. At this time of year, it happens just when evening twilight fades enough for bright stars to become easily visible.

    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

    Gibbous Mars on Feb. 23rd
    Mars may be just a featureless little blob in your telescope now, but look at the amount of detail Sean Walker was able to recover on February 23rd using a 12.5-inch scope, stacked video frames, and some fairly intense image processing. South is up. Mars was just 9.6 arcseconds in diameter at the time, and the central-meridian longitude was 22°.
    S&T: Sean Walker
    Mercury (about magnitude +0.4) is less than 2° or 3° from brilliant Venus very low in the dawn — but it's dozens of times fainter. Binoculars will help.

    Venus (magnitude –3.8, in Capricornus) is getting lower every morning. Look for it above the east-southeast horizon about 30 or 40 minutes before sunrise, far lower left of Jupiter.

    The European Space Agency's Venus Express craft continues to orbit and study the planet. The ESA has just put out a press release with closeup images and new findings about Venus's "extraordinarily changeable and extremely large-scale weather."

    Mars (about magnitude +0.1, in easternmost Taurus) shines very high in the south to southwest during evening, high above Orion. The fairly bright star near it is Beta (β) Tauri, or El Nath, magnitude +1.6 and pale blue-white. In a telescope, Mars dwindles from 9.8 to 9.0 arcseconds in apparent diameter this week.

    Jupiter (magnitude –2.0, in Sagittarius) shines low in the southeast before and during dawn. It's moving ever farther to the upper right of Venus.

    Saturn on Feb. 23
    Saturn's rings are currently tilted only 8° to our line of sight, as seen in this image taken on the evening of February 23rd when Saturn was at opposition. Two weeks earlier, the outer edge of the rings was sharply outlined by a thin line of their black shadow on the globe, but now the shadow is hidden. Note the dusky C ring just inside the broad, bright B ring. The C ring is obvious as a dark silhouette where it crosses in front of the globe. North is up.
    S&T: Sean Walker
    Saturn (magnitude +0.2, in Leo) is at opposition on the night of February 23rd. It glows low in the east as twilight fades, rises higher all evening, and stands highest in the south around midnight.

    Fainter Regulus (magnitude +1.4) is 5° west of Saturn: to its upper right after they rise. Only a little dimmer than Regulus is Gamma (γ) Leonis (magnitude +2.1), located 8° to Regulus's north. The three make an eye-catching triangle. Watch the triangle narrow in the coming weeks!

    In a telescope, look for the Seeliger effect, a brightening of Saturn's rings for several days around opposition. The reason for this? The ice particles making up the rings "backscatter" sunlight (reflect it back the way it came) more efficiently than the material in Saturn's cloud tops. When Saturn is at opposition, Earth is in the line of backscattering. A daily series of images will show this particularly well.

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

    Pluto (magnitude 14.0, in Sagittarius) is in the southeast before the first light of dawn.

    Comet Holmes, evening of Feb. 11, 2008
    in the cold and high wind. Exposures were 40 minutes blue, 40 minutes green, and 50 minutes red. The field here is almost exactly 3° wide, with north up. This comet is getting huge! So much so that I initially had a difficult time seeing it in a short exposure because it looked like the typical 'hot spot' in the center of the frame due to optical vignetting." Click image for larger view." credits="S&T: Dennis di Cicco" width="" height="" align="right"]Comet Holmes continues to grow gradually dimmer. On February 11th through suburban light pollution, Dennis di Cicco could not see it with the naked eye at all when he took the picture at right.

    On February 24th, says Tony Flanders, "the comet was barely visible naked-eye from a modestly dark rural site. It was still pretty obvious in 15x70 binoculars, and it looked to me to be about 1° by 3/4°. I could see no sign of internal detail at all." Holmes is now shrinking slightly in apparent size as it moves farther from Earth and, also, as its outermost parts fade to invisibility.

    The comet continues moving eastward in Perseus; chart.

    All descriptions that relate to your horizon or zenith — including the words up, down, right, and left — are written for the world's midnorthern latitudes. Descriptions that also depend on longitude are for North America. Eastern Standard Time (EST) equals Universal Time (UT, UTC, or GMT) minus 5 hours.

    "Rational and innocent entertainment of the highest kind."
    — John Mills, 19th century Scottish manufacturer and founder of Mills Observatory, on amateur astronomy.

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