进度计划对比分析图:This Week's Sky at a Glance for May 20 – 28

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This Week's Sky at a Glance

Some daily events in the changing sky for May 20 – 28.

by Alan M. MacRobert

Nowthat Jupiter is higher and easier to see, you can use it as a guide tolocating the other three dawn planets.These scenes are always drawn for 40° north latitude. If you're south ofthere, the view will be rotated counterclockwise by roughly yourdifference from 40° latitude. (The visibility of objects in brighttwilight is exaggerated.)Sky & Telescope diagramFriday, May 20

  • As dawn brightens early Friday,Saturday, and Sunday mornings, Venus forms a right triangle a littlemore than 2° wide with Mercury below it and faint little Mars to itsleft, as shown here. Look very low in the east using binoculars.

    Saturday, May 21

  • Arcturus is the brighteststar very high in the southeast after dark. Vega, equally bright, ismuch lower in the northeast. A third of the way from Arcturus to Vega,look for the dim semicircle of Corona Borealis, the Northern Crown, withits one moderately bright star, Alphecca.

    Two-thirds of the way from Arcturus to Vega, look for the dim Keystone of Hercules.

    Sunday, May 22

  • Faint Mars is passing about 1° above bright Venus this morning through Tuesday morning.

    Monday, May 23

  • Face northwest this eveningand look high; there's the Big Dipper, now hanging down by its handle.Just a few weeks ago it was horizontal! Star patterns appear to changeorientation fast when they pass near the zenith. The reason for this?When you're looking near the zenith, the directions toward "up" and"down" (toward and away from the zenith) differ a lot over shortdistances.

    Tuesday, May 24

  • Last-quarter Moon (exact at2:52 p.m. EDT). The Moon rises long after midnight tonightdaylight-saving time, beneath the head of Aquarius (the Water Jarasterism).

    Wednesday, May 25

  • The western twilight Archof Spring is sinking lower, but you can still catch this big landmarkwhen the stars come out. Pollux and Castor are lined up roughlyhorizontal in the west-northwest; they're about three finger-widthsapart. Look far to their lower left for Procyon, and farther to theirlower right for Capella.

    Thursday, May 26

  • Friday dawn lineup: Setthe alarm so you can be looking toward the eastern horizon about 30minutes before sunrise Friday morning. The waning crescent Moon hangshigh; far lower left of it is Jupiter. Lower left of Jupiter (by 15°) isVenus, not high at all. With binoculars or a low-power scope, look fortiny, faint Mars 2° upper right of Venus and Mercury 4° lower left ofVenus.

    Friday, May 27

  • With summer less than amonth away, the big Summer Triangle is making its appearance in theeast. Its topmost and brightest star is Vega, plain to see. Look lowerleft of Vega, by two or three fist-width at arm's length, for Deneb, thebrightest star in that area. Farther to the lower right of Vega isAltair, the last of the three Summer Triangle stars to rise (around 10or 11 p.m. daylight saving time, depending on your location).

    Watchthe Moon pass over the dawn planet lineup in the closing days of May.(The visibility of the fainter objects in bright twilight is exaggeratedhere. These scenes are always drawn for the middle of North America.European observers: move each Moon symbol a quarter of the way towardthe one for the previous date.)Sky & Telescope diagramSaturday, May 28

  • Before sunrise tomorrowmorning, look for the waning crescent Moon hanging above Jupiter, asshown at right. Use binoculars to check out the changing planetary arrayto their lower left.
  • Late tonight a 7th-magnitudestar in Ophiuchus should be occulted for up to 11 seconds by the faintasteroid 217 Eudora as seen from a track running from Florida throughOklahoma and Colorado to Oregon. See map, finder charts, and full information.



    • This Week's Sky at a Glance for May 20 – 28 This Week's Sky at a Glance for May 27 – June 4. This Week's Sky at a Glance for January 28 – February 5 This Week's Sky at a Glance for December 31 – January 8 This Week's Sky at a Glance for January 7 – 15. This Week's Sky at a Glance for January 14 – 22 This Week's Sky at a Glance for January 21 – 29 This Week's Sky at a Glance for February 4 – 12 This Week's Sky at a Glance for February 18 – 26. This Week's Sky at a Glance for March 4 – 12 This Week's Sky at a Glance for March 18 – 26 This Week's Sky at a Glance for March 25 – April 2. This Week's Sky at a Glance for April 8 – 16 This Week's Sky at a Glance for April 15 – 23 This Week's Sky at a Glance for April 22 –30 This Week's Sky at a Glance for June 3 – 6 This Week's Sky at a Glance for June 17 – 25 This Week's Sky at a Glance for July 29 – August 6 This Week's Sky at a Glance for September 8 – 17 This Week's Sky at a Glance for September 16 – 24 This Week's Sky at a Glance for June 24 - July 2 This Week's Sky at a Glance - SkyandTelescope.com This Week's Sky at a Glance February 25 – March 5. This Week's Sky at a Glance April 1 – 9