Astronomy From Your Back Yard - 7/7 to 7/13 2010
Saturday, July 10 2010 @ 11:28 am EDT
Contributed by: dgrosvold
By Dave Grosvold
This week, look for Venus shining bright in the western sky at dusk. Venus moves lower in the sky every week as the year marches on. In the evening on Saturday, July 10th, look for Regulus straight below Venus. Regulus is 150 times dimmer than Venus, and is very close to it — only about 1.2°.
On Sunday, July 11th, the New Moon occurs exactly at 2:40 PM. CDT. Mercury and the thin crescent Moon are far to the lower right of Venus in early evening Sunday, and visible only at locations with a clear view to the west. Catching them together will require some searching and the aid of a pair of binoculars. Sunday evening, Mercury and the Moon will be about 10° apart at dusk.
After Sunday, the waxing crescent Moon moves along a diagonal line south of the one described by Mercury, Venus, Mars, and Saturn. The planets lie on, or very close to the ecliptic, which is the plane of the Solar System. Watch each evening, and you will see the Moon higher and farther south than the night before, while the Crescent grows fatter until it reaches First Quarter at the end of next week.
With the darker skies due to the New Moon, this week is also a great time to look for objects in the deep sky. Deep sky objects are objects in the night sky other than individual stars and the planets of our own Solar System. The deep sky is rich with star clusters, various type of nebulae, galaxies, and supernovae remnants. In mid-summer, Scorpius is high in the south after dusk, and the Scorpion's Tail is only visible for a short window of time during this part of the year.
Scorpius is one of the most recognizable constellations in the sky, since it so closely resembles its namesake. The Scorpion's Tail is an area rich in deep sky objects, and is a great place to spend some time browsing with a telescope or binoculars. Look for Messier objects M7, the Ptolemy Cluster, and M6, the Butterfly Cluster, in the area above and to the east of the tip of the Scorpions Tail. A bit higher, in the body of the Scorpion, lies M4, a brilliant globular cluster, and one of the jewels of the night sky.
There are also many objects from the NGC, or New General Catalogue visible in the Scorpion's Tail as well. Open clusters NGC 6383, NGC 6425, NGC 6416, NGC 6242, NGC 6281, NGC 6231, NGC 6322, and NGC 6250 are in the Tail, as well as globular clusters NGC 6441, NGC 6338, and NGC 6541. Click this link for a finder chart.
This time of year, the Summer Triangle is prominent in the eastern sky about an hour after dusk. This asterism is made up of three bright stars from separate constellations: Vega, in the constellation Lyra is at the top of the triangle. Deneb, in Cyngus, is farther down on to the left (astronomers say it is North of Vega.) And finally, Altair, in the constellation Aquila, is even farther down from Vega to the right (or South for astronomers.)