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This Week's Sky at a Glance

by Alan M. MacRobert

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

Some daily events in the changing sky for November 21 – 29.

Facing southwest in twilight
Getting closer. . . .
Sky & Telescope diagram
Friday, November 21

  • The Venus-Jupiter pairing in the southwestern twilight is becoming a head-turning spectacle, as shown at right, and it will become more impressive all week. Here's a chance to do some astronomy outreach to friends and neighbors. Get them to watch these two brightest planets closing in on each other every day.

    You can point out that looks are deceiving. Jupiter and Venus may look close together, but Jupiter this week is nearly six times farther away from us than Venus is. That's part of why Jupiter is less bright even though it's a much bigger planet. The other reason is that, being farther from the Sun, Jupiter is lit much less brilliantly by the Sun's light.

    Saturday, November 22

  • The 2.1-magnitude star Nunki (Sigma Sagittarii) now sparkles 1° lower left of Venus at nightfall. Binoculars give a great view.

    Sunday, November 23

  • Planets aside, Vega is the brightest object shining high in the west after dark. Look even higher above it for Deneb. Look farther to Vega's left for Altair. These three stars form the big Summer Triangle.

    Monday, November 24

  • Vesta, the brightest asteroid, is three weeks past opposition and still magnitude 7.0. It's visible with binoculars near the head of Cetus. Use the finder chart in the November Sky & Telescope, page 67, or online. NASA's Dawn spacecraft is on its way to Vesta and will take up orbit around it in August 2011.

    Tuesday, November 25

  • This week, 1st-magnitude Fomalhaut shines at its highest due south soon after dark. Fomalhaut is one of the stars that recently made news with the announcement of the first direct images of extrasolar planets orbiting them. Another such star is 6th-magnitude HR 8977 in the western side of the Great Square of Pegasus, much higher in the south far above Fomalhaut. See our article (with finder chart).

    Wednesday, November 26

  • Spot the Pleiades cluster shining due east after dinnertime this week. Below the Pleiades glares orange Aldebaran. Much farther below Aldebaran, Orion looms up in view by 8 or 9 p.m. Below Orion, bright Sirius clears the horizon by about 10.

    Thursday, November 27

  • New Moon (exact at 11:55 a.m. EST).

    The waxing crescent Moon emerges from the sunset glare just in time to join Venus and Jupiter for their conjunction. (These scenes are drawn for the middle of North America. European observers: move each Moon symbol a quarter of the way toward the one for the previous date. For clarity, the Moon is shown three times actual size.)
    Sky & Telescope diagram
    Friday, November 28

  • The bright eclipsing variable star Algol should be in one of its periodic dimmings tonight, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 12:50 a.m. Saturday morning EST; 9:50 p.m. Friday evening PST. Algol takes several additional hours to fade and to rebrighten. Use our comparison-star chart.

    Saturday, November 29

  • With Venus and Jupiter just 2.4° apart this evening, the thin crescent Moon steps onstage about 20° to their lower right (at the time of twilight in North America), as shown here. The two planets will be closest, 2° apart, on Sunday and Monday evenings — when, coincidentally, the Moon shines near them as well.




    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).

    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 good telescopic galaxies, star clusters, and nebulae.
    Sky & Telescope
    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 classic Burnham's Celestial Handbook). Read how to use them effectively.

    Can a computerized telescope take their place? 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 and a curious mind." Without these, they wisely say, "the sky never becomes a friendly place."

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




    This Week's Planet Roundup

    Mercury is hidden in the glare of the Sun.

    As it moves farther westward in the evening sky, Jupiter has gotten small (34 arcseconds wide this week) and low, so don't be disappointed if your scope shows very little on it. Even world-class planetary imager Christopher Go recorded only this rather fuzzy view on November 16th (at 9:43 UT).

    South is up, to match the view in many telescopes. Note the white outbreak in the South Equatorial Belt near the central meridian. The CM II longitude was 277°.

    Christopher Go
    Venus and Jupiter (magnitudes –4.1 and –2.1, respectively) shine brightly in the southwest in evening twilight. Brighter Venus is to Jupiter's lower right. Watch this eye-catching pair closing in on each other daily! They're 8° apart on November 22nd and only 2.4° apart on the 29th. They reach their spectacular conjunction, 2° apart, on November 30th and December 1st — when the crescent Moon joins in too.

    In a telescope Venus is still small (16 arcseconds wide) and gibbous (71% illuminated). Jupiter is 34″ wide but has a much lower surface brightness. Being 7 times farther from the Sun, Jupiter is lit only about 1/49 as brightly.

    Mars is hidden in the glare of the Sun.

    Saturn (magnitude +1.1, in the hind feet of Leo) rises around 1 a.m. and shines high in the southeast by early dawn. Don't confuse it with similarly-bright Regulus 20° (two fist-widths at arm's length) to its upper right.

    A telescope will show that Saturn's rings have turned nearly edge on. They'll reach a minimum of 0.8° at the end of the year, then start opening again before finally closing to edge-on next September.

    Saturn on Nov. 22, 2008
    Saturn's rings were tilted just 1.5° from edge-on when Christopher Go took this image on November 22, 2008. Note their very prominent shadow on Saturn's globe. South is up.
    Christopher Go
    Uranus and Neptune (magnitudes 5.8 and 7.9, respectively, in Aquarius and Capricornus) are in the south during early evening. Uranus is now 0.1° from the similarly bright star 96 Aquarii and remains there until mid-December. Use our online article and finder charts or the chart in the September Sky & Telescope, page 63.

    Pluto is lost in the sunset.

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

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