Moon and Planets, October 2011


Look for the Big Dipper low in the northwest sky during early evenings in early autumn

As the weather changes into the cooler evenings of autumn, the stars slowly transition toward the bright winter stars.  One familiar group, known as the Big Dipper in North America, lies low in the northwestern sky during the early evening hours of October.  More, formally known as the Great Bear (Ursa Major), the stars can be found in the northern sky throughout the year.  In autumn they start the evening low in the northern sky; they are likely blocked by the trees or the neighbor’s house.

An interesting pair of stars, Mizar and Alcor, is at the bend of the dipper’s handle.  Mizar is the brighter star with dimmer Alcor nearby.  If you cannot see the close pair, use binocular.  While not physically connected in a binary star system, their close proximity makes them appear together.  Mizar is about 100 light years away with Alcor perhaps another light year away from its brighter neighbor.

Moon Phases

First Quarter   3
Full 11
Last Quarter 19
New

26

 

The positions of the visible planets on October 15, 2011

 This chart shows the positions for the visible planets as seen from north of the solar system.  Notice that Earth is between Jupiter and the sun.  Venus, Mercury, and Saturn appear near the sun.  Earth is slowly moving up to catch Mars.

Look in the west for Venus, Mercury and the moon just after sunset on October 28.

Always difficult to locate, Mercury appears near Venus in late October.  As the sky darkens on October 28, look for the moon and the reddish star Antares.  Look farther to the right of the moon for bright Venus and below it for Mercury.  You’ll need a good horizon.  Binoculars will help locate Mercury.

 
Venus is slowly emerging from behind the sun.  Early in October, Venus sets about 50 minutes after the sun.  Venus sets later than the sun throughout the month, ending the month setting about 90 minutes behind the sun.  The chart from last month’s night sky description shows the difference of times between sunset and Venus set.
 

The moon, Mars, and Regulus appear in the morning sky late in the month.

Mars is a morning star rising after 1 a.m. throughout the month.  Early in the month, it appears near the Beehive Cluster.  (See the separate article about this event.)  The moon serves as a good guide to Mars on October 21 and 22 as displayed in the chart above.  The star Regulus serves as a marker of the sun’s annual path and the plane of the solar system.  Look for Mars each morning and note how its orbital motion is carrying it closer to Regulus.  Of course, the two are not close;  Regulus is much farther away than Mars.  Mars will appear to pass Regulus next month.

Jupiter and the moon appear near each other at mid-month.

 Jupiter is the “bright star” in the eastern sky during the early evening hours.  Jupiter is at opposition and closest to Earth on October 29.  At this time the sun and Jupiter are on opposite sides of our planet.  Jupiter will rise in the east at sunset, be south around midnight and set in the west around sunrise.  It’ll be in the sky all night.  On October 12 and 13, the moon makes a nice grouping with Jupiter and the star Hamal.
Saturn appears near Spica at month’s end in the east before sunrise.
 Saturn is not visible for most of the month.  It is at conjunction on October 13.  At this time, the sun is directly between Saturn and our planet, so that Saturn is in the sky during the daytime.  Look at the planet orbit diagram above to see Saturn’s location compared to our planet.  By the end of the month, Saturn rises into the eastern sky, just before sunrise.  On Halloween, Saturn appears near Spica.  As for most observations that occur during twilight, use binoculars to see the pair.
 
Please share your observations in the comments section or ask any questions that can be answered in future articles.
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