Planets and the Pleiades

Venus skims the Pleiades on April 2, 3, and 4, while Aldebaran looks on from the side and Jupiter from far below. The blue 10° scale is about the width of your fist held at arm's length.

Sky & Telescope diagram


Friday, March 30

  • First-quarter Moon (exact at 3:41 p.m. EDT). The Moon this evening shines in the legs of Gemini, below Pollux and Castor and high above sinking Betelgeuse.
  • Summer begins in the northern hemisphere of Mars. As temperatures there have risen for the last few months, amateur scopes have been showing Martian North Polar Cap dwindling to become tiny.

    Saturday, March 31

  • The Moon shines high in the southwest this evening. It forms a gently curving line (as seen from North America) with Pollux and Castor to its upper right and Procyon below it.

    Sunday, April 1

  • This is the time of year when Orion, declining in the southwest after dark, displays his three-star Belt more or less horizontally. The Belt points left toward Sirius, and right toward Aldebaran and (farther on) brilliant Venus.
  • If we told you Mercury shines at the zenith at midnight, you'd know it was April Fool's, right?

    Moon, Regulus, and Mars at dusk

    On the other side of the sky, watch the Moon pass icy blue-white Regulus and fiery yellow-orange Mars. (These scenes are drawn for the middle of North America. For clarity, the Moon is shown three times actual size.)

    Sky & Telescope diagram


    Monday, April 2

  • Venus is passing through the outskirts of the Pleiades this evening through Wednesday evening, as shown above. Binoculars or a wide-field telescope give a fine view of the delicate cluster behind Venus's overpowering glare.
  • The waxing gibbous Moon forms a slightly curving line with Mars and Regulus, as shown at right.

    Tuesday, April 3

  • The Moon now forms the bottom point of a narrow triangle with Mars and Regulus, as shown at right.
  • Venus is the closest it will come to the middle of the Pleiades. This evening for the Americas, Venus is passing just ½° southeast of Alcyone (the brightest Pleiad) and ¼° south of the Atlas-Pleione pair. Venus is magnitude –4.5, which means Alcyone, at magnitude 2.85, is 900 times fainter!

    Moon, Spica, Saturn after dark

    As the Moon becomes full, it approaches Spica and Saturn in the east after dark.

    Sky & Telescope diagram


    Wednesday, April 4

  • Two planet-and-star pairings mark the evening sky of spring 2012. After nightfall this week, Mars shines high in the south with Regulus to its right (by 5°). As evening advances, Saturn rises into view low in the east-southeast with Spica to its right (by 5½°).

    Thursday, April 5

  • The Moon is nearly full this evening. Look left of it for Gamma (γ) Virginis (Porrima), a tight telescopic double star. (Its separation is 1.8 arcseconds this spring; it's widening year by year). Look farther lower left of the Moon for steady-shining Saturn and twinkly Spica, as shown here. And look to the Moon's lower right for the four-star pattern of the constellation Corvus, the Crow.

    Venus, Pleiades, Jupiter at dusk

    By now the Pleiades are out from under the glare of Venus.

    Sky & Telescope diagram


    Friday, April 6

  • Full Moon (exact at 3:19 p.m. EDT). This evening the Moon shines in the east with Spica a little to its left and Saturn farther left — a pretty lineup, as shown here. Farther to the Moon's right, look for the four-star pattern of Corvus, the Crow. Much farther to the upper left (outside the picture here) is bright Arcturus, the "Spring Star."

    Saturday, April 7

  • The bright Moon rises around the end of twilight below Saturn and Spica in the east-southeast. Later in the evening the three shine higher: a long, narrow triangle with the Moon at the bottom.

    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).

    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 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 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 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

    Venus on March 20, 2012

    Venus imaged in five colors. To the eye Venus's clouds are almost always pure blank white, but stacked-video imaging can sometimes pull out subtle features. S&T's Sean Walker caught the cloudy planet at dichotomy late on the afternoon of March 20th, imaging with his 12.5-inch reflector through near-ultraviolet (UV), blue (B), green (G), red (R), and near-infrared (IR) filters during excellent seeing.

    S&T: Sean Walker

    .

    Mercury is deep in the glow of sunrise.

    Venus and Jupiter are moving ever farther apart in the western twilight, as shown at the top of this page. Venus is the brighter one, on top. Jupiter is 14° below it on March 30th and 19° below it by April 6th. These are the two brightest celestial objects after the Sun and Moon, being magnitudes –4.5 and –2.1 right now, respectively.

    Venus skims the little Pleiades star cluster this week. It's closest to the Pleiades' center on April 3rd. Binoculars help show the delicate stars behind Venus's bright glare.

    In a telescope, Venus is a little less than half lit and 25 arcseconds tall. Jupiter shows a much lower surface brightness, being farther from the Sun, but its apparent diameter is a little larger: 34″. This is small for Jupiter, and in addition Jupiter is disappointingly fuzzy at its ever-lower altitude.

    Mars on March 20-21, 2012

    The bland side of Mars was presented to Earth when S&T's Sean Walker took this image on the night of March 20–21. Since then another side has turned our way, when Mars is viewed in the evening hours for eastern North America.

    South is up, and celestial east is to the right (the following side; Mars's morning side). Notice the clouds, the much-shrunken North Polar Cap, and the dark collar that has been laid bare around the retreating cap.

    S&T: Sean Walker


    Mars (magnitude –0.7) shines bright fire-orange under the belly of Leo. Regulus is 5° to Mars's right in the evening, and Gamma Leonis is 7° above it. Mars was at opposition on March 3rd. Now it's fading and shrinking as Earth pulls ahead of it along our faster, inside-track orbit around the Sun. But at least Mars is shining higher in the evening sky now. It's highest in the south by around 10 or 11 p.m. daylight-saving time.

    In a telescope Mars is about 12.4 arcseconds wide. Its North Polar Cap has shrunk to become tiny; spring is turning to summer in Mars's northern hemisphere. See our Mars map and observing guide in the April Sky & Telescope, page 50.

    Saturn (magnitude +0.3, in Virgo) rises around the end of twilight and glows highest in the south around 1 or 2 a.m. It will come to opposition on April 15th. Shining nearly 6° to Saturn's right is Spica, about half as bright at magnitude +1.0 and bluer. In a telescope Saturn's rings are tilted 14° from our line of sight.

    Uranus and Neptune are hidden in the sunrise.

    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 Daylight Time (EDT) equals Universal Time (also known as 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.

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