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The Sky This Week, 2011 September 13 - 20

Waiting for the Moon to leave...
Harvest_Moonrise_110912_01small.jpg
Harvest Moon rising over Washington, DC
imaged from the roof of the U.S. Naval Observatory,
2011 September 12, 19:28

The Moon continues to light the evening sky during the first half of the week as she wanes from the Full phase. Last Quarter occurs on the 20th at 9:39 am Eastern Daylight Time. Look for Luna rising with bright Jupiter on the evenings of the 15th and 16th. She passes three degrees south of the rising Pleiades star cluster on the night of the 17th. Finally, by week’s end, the Moon abandons us for the morning sky.

As the Moon wanes the early evening skies become darker, which bodes well for those who wish to track down the two celestial transients that have kept our attention over the past couple of weeks. Comet 2009 P1 Garradd drifts slowly westward among the stars of the constellation Hercules just to the western side of the Summer Triangle. Despite the Full Harvest Moon we were able to track the comet down with USNO’s 12-inch refractor on last Monday’s evening tour. From a darker location (even the suburbs will do) the 8th magnitude fuzzball should be readily visible in binoculars or a small telescope by 9:00 pm EDT as the weekend approaches. Comet Garradd is drifting through a field of fourth and fifth magnitude stars, passing within a degree of the fourth magnitude star 110 Herculis on the evenings of the 13th through the 15th. A finder chart for the comet for the next two weeks may be found here, with its position plotted for 9:00 pm. The comet is moving from “left” to “right” against the stars.

Supernova 2011fe continues to brighten in the relatively nearby galaxy Messier 101. Its most recent reported brightness estimate was magnitude 9.9, which should make it a fairly easy target for small to medium aperture telescopes from dark locations. SN 2009fe is the brightest supernova to appear in northern skies since the eruption of a 6th magnitude outburst in the nearby Andromeda Galaxy in 1885. As the Moon wanes over the next few weeks many telescopes, both amateur and professional, will be turned toward this stellar cataclysm. If you do manage to track it down, consider that you are seeing the light from a single star that is some 21 million light-years away!

Much closer to home is the bright planet Jupiter, which can now be seen cresting the eastern horizon at around 9:30 pm EDT. Old Jove rises four minutes earlier on each successive night right now, so he’ll soon be a fixture in the overnight hours. He gets a visit from the rising Moon on the nights of the 15th and 16th. Through the telescope he has returned to his more-or-less “normal” appearance, sporting his two dark equatorial cloud belts and his ever-changing Galilean moons. Late-night skywatchers will have a good view of the giant planet by around midnight, while early risers can see him high in the southern sky as morning twilight begins.

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