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The shining —what’s twinkling above

February 21, 2012
By AILEEN O'DONOGHUE , Adirondack Daily Enterprise

The moon will be new at 5:36 this evening. That means it will be aligned with the sun in our sky and, thus, invisible. It may be visible Wednesday night as a very thin crescent if you have a low western horizon. By Thursday evening, a thicker crescent will be easily visible as it will be 20 degrees above the west southwestern horizon at sunset and set an hour and 20 minutes after the sun.

Also in the western sky, Venus continues to shine brightly every evening and Jupiter has been gradually moving toward it through the late fall and winter. Now that Jupiter and Venus are separated by less than 20 degrees, it will be much easier to observe the distance between them changing as it closes to 3 degrees on March 13.

Meanwhile, as shown on the diagram, the waxing moon will journey across the sky to align with three planets in turn. On Feb. 25, the moon will be 3 degrees north of Venus (the thickness of your finger held at arm's length is about 1 degree). On the next night, it will be about 4 degrees north northwest of Jupiter. On Feb. 28, the moon will pass 4 degrees south of the Pleiades on its way to First Quarter the following night.

Article Photos

On the first and second of March, it will be 5 degrees southwest then 5 degrees southeast of the summer solstice, where the sun will be on June 20.

On March 3, Mars will be at opposition, opposite the sun in our sky and thus rise as the sun sets (it will actually rise 18 minutes before the sun sets because it's north of the celestial equator and the sun is still south of it. If both were on the celestial equator, they would rise and set simultaneously).

On March 7, the full moon will be 10 degrees south of Mars and join it on the eastern horizon, rising 21 minutes after Mars and 26 minutes before sunset. As well as showing the moon's motion across the sky the diagram shows the motions of the planets relative to the stars with grey circles.

Since the stars shift 1 degree westward every day, it will appear more that the entire diagram shifts with Venus rising only slightly from its position tonight. Jupiter will move with the sky as it is moving slowly in its prograde, eastward motion (note the circles showing its position every five nights or so overlap) so it will appear to move toward Venus.

The two bright planets will nearly meet on March 13, then Jupiter will sink toward the horizon as Earth's faster orbital motion leaves the giant planet on the far side of the sun.

Venus will continue to rise slightly higher in the sky at sunset until March 27 as discussed in The Wilderness Above on Dec. 27, 2011.

As Jupiter sinks toward the western horizon, Mars rises from the eastern. Already the brightest object in the east at sunset, it's red hue can't be missed. Due to the shapes of Earth's and Mars' orbits, the red planet will be closest to Earth, a mere 63 million miles away, on March 5, two days after opposition. It's moving rapidly westward in its retrograde loop and will reach the line between Regulus and Chertan, the belly of the lion, on April 15 when it pauses to resume its prograde motion. Thus Mars appears to be headed for a conjunction with Venus, but these two nearest neighbors of Earth will be 75 degrees apart at their closest since Venus will begin moving back toward the sun after March 27 and Mars will resume its eastward motion in April.

We will be able to watch Mars cross from the eastern to the western horizon through the spring and summer as it moves from beneath Leo through Virgo.

On the eastern side of Virgo in early August, it will form a trio, three celestial objects within a circle 5 degrees or less, with Saturn and Spica. There's one more planet that we have a chance to observe over the next three weeks as Mercury makes one of its fleeting appearances in the evening sky.

Tonight it will be 10 degrees above the horizon at sunset and set about an hour after the sun. It is moving higher in the evening sky as it swings away from its alignment on the far side of the sun on Feb. 7. It will be highest on March 5, then sink back toward the horizon. If you manage to spot the thin crescent moon tomorrow evening between 5:45 and 6:15, Mercury will be just to its left at the same height above the horizon.

After that, just look for the brightest object between Venus and the horizon and that will, most likely, be Mercury since there are no bright stars in this part of the sky. I'll have more to say about this smallest and fastest of the planets in my next column.

If you have questions about the nature and motions of the moon and planets or any other astronomical topic, please visit the Adirondack Public Observatory website at apobservatory.org or email me at aodonoghue@stlawu.edu.

 
 

 

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