Sky at a Glance | May 18th, 2007

Some daily events in the changing sky for May 18 – 26.

Looking west-northwest in twilight
Watch the waxing crescent Moon march up day by day to a spectacular conjunction with Venus on the 19th. This scene is 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 drawn three times its actual apparent size.
Sky & Telescope diagram

Friday, May 18

  • The thin Moon shines to the lower right of Venus this evening, as shown here. Far below the Moon, can you spot Mercury yet? It's getting higher every day.

    Saturday, May 19

  • Venus pairs up with the crescent Moon for a head-turning spectacle high in the west during twilight, and lower in the west after dark. They'll appear less than 2° apart for viewers throughout North America.

    Sunday, May 20

  • This evening the waxing Moon shines left of Pollux and Castor and upper left of bright Venus.

    Monday, May 21

  • The Moon, Saturn, and Regulus form a nearly straight line tonight, in that order from lower right to upper left.

    Tuesday, May 22

  • For North America, the Moon is framed between Saturn (to the Moon's right or lower right) and Regulus (to the left or upper left).

  • For Europe, however, the Moon's dark edge occults (covers) Saturn in late afternoon or early evening.

    Wednesday, May 23

  • First-quarter Moon (exact at 5:03 p.m. Eastern Daylight Time).

    Thursday, May 24

  • Springtime is galaxy time. Have you ever worked your way with a telescope through the Virgo Galaxy Cluster? See Sue French's Deep-Sky Wonders article and chart in the May Sky & Telescope, page 65.

    Friday, May 25

  • After sunset at this time of year, when the stars begin to come out in twilight Vega is at the same height in the northeast as Capella is in the northwest. These are the brightest stars in the May evening sky — along with Arcturus very high in the southeast.

    Saturday, May 26

  • With Bootes high in the evening sky, now's a fine time to check in on the semiregular red variable star V Bootis using big binoculars or a small scope. See the May Sky & Telescope, page 62.

    Spica and Corvus
    SIGNS OF SPRING. Spica (upper left) and the constellation Corvus, the Crow (right), are among the most familiar highlights of the spring sky. Look for them in the south right after dusk this week.
    Akira Fujii

    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 standard is Sky Atlas 2000.0) and good deep-sky guidebooks (such as Sky Atlas 2000.0 Companion or the enchanting though somewhat dated Burnham's Celestial Handbook). Read here how to use them most effectively.

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

    This Week's Planet Roundup

    Mercury (about magnitude –0.5) is visible low in the sunset, getting higher every day. Look for it 45 to 60 minutes after sunset above the west-northwest horizon, far lower right of Venus. The much fainter star Beta Tauri is above Mercury early in the week (as shown at the top of this page), but to the right of it by week's end.

    Venus in ultraviolet and infrared, May 20, 2007
    Sky & Telescope's Sean Walker continues to image Venus as the planet slowly wanes and enlarges. On May 20th its clouds were full of detail in both ultraviolet (UV) and near-infrared (IR) light. The Universal Times of the exposures are given. Walker made the color rendition by showing ultraviolet as blue, infrared as red, and adding a green channel created by interpolating between the two.
    S&T: Sean Walker

    Venus (magnitude –4.3, in central Gemini) is the brilliant "Evening Star" shining in the west during and after twilight. This month Venus is at its peak evening height for the year.

    Above Venus are Pollux and Castor. Watch them slide down toward the bright planet day by day. A telescope will show that Venus is nearing its half-lit phase, while enlarging a little week by week.

    Mars (magnitude +0.9, in Pisces) is still low in the east-southeast during dawn. Though it remains pathetically tiny for now — a mere 5.5 acrseconds in apparent diameter, a featureless little blob in most scopes — be patient. Earth is catching up to Mars in our faster orbit around the Sun. When we pass it this December, Mars will appear nearly 16" wide. That still won't be very large, however; Mars was 25" wide around its opposition in August 2003.

    Jupiter with Red Spot, May 19, 2007
    Using an 11-inch telescope, a video camera, and the frame-stacking technique, Christopher Go of Cebu City, Philippines, made this image of Jupiter on May 19, 2007. The Great Red Spot was almost at the central meridian at 17:22 Universal Time. Notice the Red Spot's dark central mark, dark outer ring, and the white Red Spot Hollow. The small dark dot to its right (preceding) is not a satellite shadow but a real (and persistent) marking. The Equatorial Zone remains dusky and festoon-ridden, and the North Equatorial Belt is very wide, dark, and red. North is up. Click image for a May 11th view of Jupiter's opposite side.

    Jupiter (magnitude –2.6, in southern Ophiuchus) rises in the east-southeast around 9 or 10 p.m. daylight saving time and dominates the south to southwest in the early-morning hours. Antares, less bright, sparkles 8° or 9° to Jupiter's right during the evening and lower right before dawn.

    Saturn (magnitude +0.5, at the Leo-Cancer border) shines high in the west during evening. It's far to the upper left of bright Venus (by 35° to 30° this week). Watch these two closing in on each other, on their way toward their close conjunction at the end of June.

    Regulus, less bright at magnitude +1.4, is 11° to Saturn's left or upper left. North of Regulus is 2nd-magnitude Algieba (Gamma Leonis), a fine telescopic double star.

    Uranus (magnitude 6, in Aquarius) is low in the east-southeast before dawn, upper right of Mars.

    Neptune (magnitude 8, in Capricornus) is higher in the southeast before dawn.

    Pluto (magnitude 14, in northwestern Sagittarius) is not far from Jupiter in the south during the early morning hours.

    All descriptions that relate to your horizon — including the words up, down, right, and left — are written for the world's midnorthern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America. Eastern Daylight Time (EDT) equals Universal Time (UT, UTC, or GMT) minus 4 hours.

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