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Photo of the Week.. Orion, Sirius, and memories of winter.

Astronomy news for the week starting Friday, July 27, 2012.

This is the week of the full Moon, which takes place the night of Wednesday, August 1, with the Moon close to or actually rising for those in North America. This being summer with the S un far to the north of the celestial equator, the full Moon will appear well to the south of that circle, among the dim stars of Capricornus to the east of the Winter Solstice in Sagittarius. Prior to its fullness, the Moon will be fattening in the waxing gibbous phase, when it rises in the late afternoon or early evening, the last part of the week seeing a bit of the waning gibbous. On the night of Monday, July 30, the Moon passes just south of dim Pluto, occulting it as seen from Antarctica and far southern South America. With Pluto 1500 times fainter than the eye can see, the event is quite unobservable. The day before, the Moon passes perigee, where it is a bit closer to the Earth than average, the difference in angular size also not sensible to the eye.

Aside from the glorious summer constellations, evening's Mars and Saturn (well into the west as the sky darkens) still draw the eye, the two planets along with the star Spica (all in Virgo) making a fine triangle with Mars at the western apex. All three are about the same brightness, Saturn just besting the others. Relatively nearby, Mars is moving about half a degree per night to the east against the background stars, fast enough to notice from night to night. Much more distant Saturn pretty much just sits there, however, to the north of Spica, letting Mars catch up to it, the two destined to pass conjunction the night of August 16. Mars now sets at 11 PM Daylight Time, Saturn just half an hour later.

The morning sky displays an equally fine, if not better, sight. As Mars approaches Saturn, Jupiter pulls away now from Venus. The giant planet rises before 2 AM, an hour before Venus lofts itself over the horizon. Just to the north of the Hyades in Taurus (hard to see under Moonlight), Jupiter will pass north of Aldebaran just before it rises the morning of Friday the 3rd. Jupiter and Venus then march across the sky to the west until dawn starts to take them away. Inward of Venus, Mercury passes inferior conjunction with the Sun on Saturday the 28th.

The bright Moon wipes out much of the constellation figures, though the brightest of stars still shine through, notably those of the Summer Triangle, which falls from overhead to south around midnight. Vega is at the northwestern apex, Deneb at the northeastern, Altair at the southern. Well into the west, look for Arcturus well to the north of the Saturn/Spica/Mars configuration.
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