Skywatch Line for Friday, November 22, through Sunday, November 24, 2019

This is Dudley Observatory’s Skywatch Line for Friday, November 22, through Sunday, November 24, written by Sam Salem.

On Friday, Sun rises at 6:56am and sets at 4:27pm; the waning crescent Moon rises at 1:51am and sets at 2:35pm. The Moon reaches perigee, the closest point in its orbit around Earth, at 2:41am on Saturday. It then lies 227,867 miles away from Earth. Moon, Mars, and Mercury form large triangle in morning twilight on Sunday.

On Saturday, Venus is 1.5 degrees lower left of Jupiter in evening twilight. Jupiter lies above Venus on Sunday night, Venus appears to the left and slightly below Jupiter. The best views of this conjunction will come with the naked eye or binoculars. Venus sets few minutes before 6pm and Jupiter sets few minutes after 6pm.

Saturn resides among the background stars of constellation Sagittarius the Archer. Saturn shines at magnitude 0.6 and appears significantly brighter than any of its host constellation’s stars. A small instrument shows Saturn’s 16″-diameter disk and spectacular ring system, which spans 35″ and tilts 25 degrees to our line of sight. Saturn sets around 7:40pm.

The waning crescent Moon makes a convenient guide for spotting Mars, at 1.7 magnitude, on Sunday morning. Look for the 6-percent-lit Moon about 15 degrees high in the east-southeast an hour before sunrise. The Red Planet lurks 4 degrees to Moon’s right. Look for magnitude –0.4 Mercury, 8 degree below the Moon. Mars rises around 4:30am and Mercury rises around 5:20am.

Try to spot Uranus, at 5.7 magnitude, with the naked eye this weekend. Uranus, in southern constellation Aries, is well up in the east by 8pm and highest in the south around 10pm.

The Andromeda Galaxy, Messier 31, can be seen with the naked eye as a hazy dash of light directly overhead around 9pm from a dark-sky site. Look for it atop a stack of three modestly bright stars in Andromeda. Start with second-magnitude Beta Andromedae. Look above that to Mu Andromedae, then above Mu to Nu Andromedae. Directly above Nu, the Andromeda Galaxy shows as a fuzzy, elongated slant of light of magnitude 3.4. From a very dark site, M31 may appear 0.5 degree across, about as wide on the sky as our Moon. Telescopic observers can also see M32 and M110, M31’s elliptical satellite galaxies. Andromeda Galaxy is 2.5 million light-years away. In 1925, astronomer Edwin Hubble was the first to resolve its variable stars, using Mt. Wilson’s 2.5-meter telescope to prove M31 is a gigantic galaxy like ours.

Later at night, enjoy the sight of some fine double stars in the constellations Andromeda and Aries. Gamma Andromedae, or Almaak, is an excellent example of contrasting colors within a binary star system. Like Albireo of our summer nights, Gamma Andromedae’s two main stars shine orange and blue. The fainter blue component is itself a binary, but at magnitude 5.0 splitting this close pair may not be easy even at high magnification. The brighter star is a K-type giant of magnitude 2.3. Star’s color is dependent on its surface temperature. The orange-tinted star is the cooler of the two, while the bluish component radiates hotter. Just below Almaak is Gamma Arietis. This binary features blue-white stars shining at 4.6 and 4.7 magnitude, an almost evenly matched pair of hot, A-type stars. Astronomer Robert Hooke was the first to describe this double in 1664.

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