Skywatch Line for Monday and Tuesday, December 2nd and 3rd, 2019

This is the Skywatch Line for Monday and Tuesday, December second and third, written by Joe Slomka.

The Sun sets at 4:22 PM; night falls at 6:03. Dawn begins at 5:27 AM and ends with the Sun rising at 7:08.

Monday’s Moon, in Capricornus, rose after Noon, is highest at 5:08 PM sets at 10:13 PM and is 39% illuminated. Tuesday’s Moon, in Aquarius, appears 47% lit, is highest at 5:53 PM and sets at 11:14 PM. The Moon turns officially “First Quarter” Wednesday at 1:58 AM.

Jupiter, Venus and Saturn, all in Sagittarius, continue to hug the western horizon. At about 40 minutes after sunset, Jupiter glows with minus 1st magnitude, but sits only 6° above the horizon; it sets at 5:35 PM. Venus, to Jupiter’s upper left, blazes with minus 4th magnitude appears about 49% lit and sets at 6:05 PM. Saturn, 11° to Venus’ upper left, shines with zero magnitude and is high enough for telescopic glimpses of its famous ring system, before it sets at 6:58 PM.

Night reveals Neptune and Uranus. Neptune, still in Aquarius, glows with 8th magnitude, is a tiny 2 arc-seconds in size, appears highest at 6:18 PM and sets at 11:53 PM. The nearby Moon may hinder observation with its brilliance. Uranus, in Aries, is brighter with 5th magnitude and appears a bit larger than Neptune. Its distance from the Moon may assist in observation. Uranus is highest at 9:13 PM and sets at 4:01 AM. Finder charts for these planets are available from astronomy magazines and websites.

Civil Dawn sees Mars, in Libra, about 20° high in the eastern sky. It displays a first magnitude red dot, about 4 arc-seconds in size. Mars rises at 4:29 AM. Mercury saw its highest point last week and is starting a rapid decline. Rising also in Libra at 5:26 AM, it shines with minus zero magnitude but appears larger than Mars and is 61% lit. The intrepid early morning observer should work quickly due to the brightening pre-sunrise sky.

French astronomer Pierre Mechain discovered M75 in 1780, in the constellation Sagittarius. He told his good friend comet hunter Charles Messier, who listed this object as number seventy-five in his list of comet lookalikes. In 1784, British astronomer William Herschel estimated the distance to this “nebula without stars” as six thousand light-years. We now know that M75 is a globular star cluster. Globular clusters are usually found around galaxy halos and Globulars bulges. Globulars may contain up to a million stars and are quite large, in a sphere about 100 light-years across. These stars are quite old. Modern estimates place M75 at about fifty-nine thousand light-years away. Astronomers also describe it as one of globulars compact globulars in the sky. Only the largest telescopes can resolve the cluster into individual stars.

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