This is the Dudley Observatory Skywatch Line for Wednesday, December 25th, and Thursday, December 26th, written by Louis Suarato.
This lunar cycle’s New Moon phase occurs at 12:13 a.m. Thursday. Venus is the highlight of the evening sky, shining at magnitude -3.94, 15 degrees above the southwestern horizon as Saturn is setting around 5:45 p.m. in the west-southwest. Venus sets at 7:04 p.m. with 1st magnitude star Fomalhaut to its south. When you’re observing Fomalhaut, you’re looking at one of the brightest stars known to have a planetary system, second only to Pollux. Mars rises at 4:14 a.m. in the constellation Libra.
Keep an eye on Betelgeuse, currently the second brightest star in the constellation Orion. This variable star has dimmed considerably recently. Betelgeuse is about 700 times larger than our Sun, and about 4,000 degrees cooler. This red supergiant star also sheds about 7,500 times more energy than the Sun. These facts have led astronomers to believe Betelgeuse is at the end of its life which will end in a supernova event. Observers have recorded Betelgeuse’s brightness to have peaked in 1933 and 1942 at magnitude 0.2. In 1927 and 1941, the star dimmed to magnitude 1.2. Recent observations have indicted Betelgeuse is now dimmer than Aldebaran, which shines at magnitude 0.85. Eventually, Betelgeuse will exhaust all the fuel it has, and its core will collapse. This causes a detonation of the star which creates a Type II supernova. The Astrophysical Journal, in an article published on February 23, 2016, estimated a supernova created by the demise of Betelgeuse could be as bright as magnitude -12.4, about the same as the Full Moon, and could be seen during the day.
Thursday morning, at 5:45, an extremely bright, -3.5 magnitude International Space Station will appear mid-sky above Ursa Minor. The ISS will pass through the Little Dipper and Cygnus before heading into the northeastern horizon.