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The Sky This Week, 2009 November 3 - 10

Stories of Seven Sisters

The Moon wanes in the morning sky this week, passing through the stars of the rising Great Winter Circle.  Last Quarter occurs on the 9th at 10:56 am Eastern Standard Time.  Look for Luna’s nearly full disc to occult the southernmost stars of the famous Pleiades star cluster between 10:00 pm on the 3rd and 2:00 am on the 4th.  The Moon will pass about four degrees southeast of ruddy Mars during the morning hours of the 9th.  The following morning you’ll find her creeping up on the bright star Regulus, lead star of the constellation of Leo, the Lion.

The passage of the Moon through the Pleiades draws our attention to one of the most unique sights in all of the sky.  While you may need binoculars to pick out the stars of the “Seven Sisters” slipping behind and then out from Luna’s bright face, in a few more nights you should be able to pick this group out from suburban skies with relative ease.  Among many stories from Greek mythology they represented the seven daughters of Atlas, who were constantly being pursued by Orion.  Zeus took pity on Atlas due to his burden of having to carry the world on his shoulders and transformed the daughters into stars, forever staying ahead of their aggressive suitor.  Of course, Zeus consorted with many of the daughters himself, and these became the brightest members of the group.  Most people can make out six or seven stars in the cluster with the naked eye on a moonless night in a dark location.  Some very keen-eyed people can see over a dozen.  Binoculars will show several dozen members, and the view from a dark site in a small “rich-field” telescope will yield up hundreds more.  The Pleiades form a true cluster with a total of some 1000 stars.  The brightest of these are hot blue “giant” stars that outshine our Sun by several factors of a hundred.  They are among some of the youngest stars known in the sky, having formed some 100 million years ago.  The cluster is located at a distance of about 440 light-years from Earth.  Popular folklore links the appearance of the Pleiades in the evening sky with the onset of winter and its attendant storms.  Indeed, some of my most memorable views of the cluster come from watching them rise over snow-covered New England fields during the winter holidays.

Bringing our attention back to the early evening, we now find Jupiter astride the meridian as evening twilight gathers.  With sunset now occurring at around 5:00 pm, Old Jove is at his highest about an hour later.  The giant planet still dominates the early part of the evening, but by 10:00 pm he’s beginning to settle into the trees, and he sets well before midnight.  You still have several hours to enjoy viewing him through the telescope, however, and you’ll be amply rewarded for doing so.  At the very least you’ll see the same sight that was first glimpsed by Galileo some 400 years ago in his first telescopic views of the heavens.

At about the same time that Jupiter departs the scene, another planet rises to take his place.  Ruddy Mars is drifting slowly eastward against the faint stars of the constellation Cancer, the Crab, and he’s considerably fainter than Jupiter, but his distinctive pinkish hue instantly betrays his identity.  Those of us who have enjoyed viewing Old Jove will have to really squint to find much detail on the red planet.  His apparent disc is only about ¼ the size of Jupiter’s!

Golden Saturn is best saved for pre-dawn viewing.  The ringed planet will be high enough by the start of morning twilight to get a few decent peeks at his nearly edge-on rings and brighter moons.