Skywatch Line for Friday, January 15, through Sunday, January 17, 2016

This is Dudley Observatory’s Skywatch Line for Friday, January 15, through Sunday, January 17, 2016, written by Alan French.

The Moon reaches first quarter early Saturday evening, making this weekend ideal for observing the lunar landscape at a very reasonable hour. The Moon, slightly less than half full, will be due south and highest at 5:00 pm on Friday night. It will be due south at 5:53 pm on Saturday and at 6:46 pm Sunday.

As we’ve noted before detail stands out most near the terminator, the line dividing the sunlight portion of the Moon from darkness. As it moves from new to full this is the line of sunrise marching across the Moon. Along it shadows are long, so detail stands out exceptionally well. Even binoculars will shows some of the larger craters, and any telescope provides a memorable view. Although the features are unchanging, the lighting varies from hour to hour, greatly changing the appearance of the landscape.

The Lunar Reconnaissance Orbiter (LRO), which reached the Moon on June 23, 2009, was placed in a polar orbit for lunar mapping. In late 2010 the most accurate topographic map, based on date from the LRO, was publicly released. The LRO has also captured photographs showing the Apollo landing sites. These photos show evidence of our presence on the Moon, including the bases of the lunar landers, instruments left for lunar studies, and tracks left by the rovers.

You can see the LRO images of the Apollo landing sites at this web site.

At 9:30 pm bright Capella is high overhead. Capella is the sixth brightest star in the night sky and the closest first magnitude star to the pole. It is the brightest star in Auriga, the Charioteer. Including Capella, a rough pentagon of five stars marks the outline of Auriga.

If you are up not long before morning twilight infringes on the eastern sky, perhaps around 5:30 am, four planets stretch across the sky. Very low is brilliant Venus, a bit east of southeast. Higher and more toward the southeast is yellowish Saturn. To the south southeast is reddish Mars, and higher and toward to the south southwest is bright Jupiter.

On our faster, inner orbit, Earth overtakes and passes Mars about every two years and fifty days. Because of Mars’ eccentric orbit, the distance between the Earth and Mars varies. This year begins a series of relatively close approaches. From late April to late July Mars will be close enough for good telescope views. Unfortunately for those of us up here in the northern latitudes, the planet will be relatively low in the sky. Views through this thicker layer of the Earth’s atmosphere tend to be less steady and show less detail than when Mars is high in the sky.

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