长建驾校官网:This Week's Sky at a Glance for July 29 – August 6

This Week's Sky at a Glance
Some daily events in the changing sky for July 29 – August 6
by Alan M. MacRobert
Friday, July 29
Look southeast after dark, alittle more than halfway from the horizon to straight overhead, for thebright star Altair. It's the eye of Aquila, the Eagle. At its distanceof 17 light-years, Altair is one of our closest stellar neighbors. It's afast-spinner, so much so that it's strongly elliptical rather thanround — not that you can see any sign of this with any ordinaryinstrument!
Saturday, July 30
Now that summer is faradvanced, the glowing band of the Milky Way forms a vast arch highacross the sky after darkness is complete — if you're one of the fewlucky people not living under light pollution. The Milky Way runs fromPerseus and Cassiopeia low in the north-northeast, up and across the bigSummer Triangle very high in the east, and down to Sagittarius andScorpius low in the south. How much of it can you see?
New Moon (exact at 2:40 p.m. Eastern Daylight Time).
Thetick marks show Vesta's location at 0:00 Universal Time on the datesindicated. It's moving toward the lower right in August. This is anarrow closeup; click for our larger, printablefinder charts for Ceres and Vesta for 2011.
Sky & Telescope diagram
Sunday, July 31
The brightest asteroid, 4Vesta, is at opposition this week, shining at magnitude 5.6 inCapricornus. It's an easy find in binoculars in late evening and can beseen with the unaided eye from a dark site. Use the finder chart in theAugustSky & Telescope, page 53, or ourVesta and Ceres finder charts online. The Dawn spacecraft is now orbiting Vesta,taking pictures and gradually working its way down to a much lower orbit, which it will reach in early 2012.
Monday, August 1
As August begins, brightVega crosses nearest the zenith around 11:00 p.m., depending on whereyou're located east-west in your time zone. How accurately can you timewhen this event happens for you? Vega goes exactly through the zenith ifyou're at latitude 30° north.
Tuesday, August 2
Before the waxing Moonstarts lighting the evening sky in a few days, try hunting faintgalaxies on the arched back of Draco using Ken Hewitt-White's "GoingDeep" article and charts in the AugustSky & Telescope, page 62.
Thewaxing Moon reappears at dusk this week below Saturn and Spica. (Thesescenes are drawn for the middle of North America. European observers:move each Moon symbol a quarter of the way toward the one for theprevious date. The Moon is shown three times its actual apparent size.The blue 10° scale is about the size of your fist held at arm's length.)
Sky & Telescope diagram
Wednesday, August 3
The waxing crescent Moon is below Saturn at dusk, as shown above.
Thursday, August 4
This evening the Moon is below Spica at nightfall, as shown above.
Friday, August 5
The Moon lines up left of Spica and Saturn at dusk.
Mars, low in the east-northeast just beforethe first light of dawn,is passing less than 1° south (lower right) of the star cluster M35 inGemini on Saturday and Sunday mornings. Use binoculars or a telescope.
Saturday, August 6
First-quarter Moon (exact at 7:08 a.m. EDT). The Moon is in the middle of Libra, to the right of upper Scorpius.