This is the Dudley Observatory Skywatch Line for Wednesday, July 22nd, and Thursday, July 23rd, written by Louis Suarato.
The 7% illuminated, waxing crescent Moon sets at 10:07 p.m. Wednesday, in the constellation Leo. While the Moon is setting, Jupiter and Saturn will be rising over the southeastern horizon in the constellation Sagittarius. The two gas giants will be separated by 6 degrees. Saturn and Jupiter have recently reached opposition and are in an ideal situation for viewing as they remain in the sky the entire night. Mars joins Jupiter and Saturn when it rises at 11:36 p.m. in Pisces. Venus rises at 2:40 a.m., below its Taurus’ brightest star, Aldebaran. Mercury reaches its greatest elongation on Wednesday, at 20 degrees from the Sun, but may be too close to the glow of sunrise to see.
Comet C/2020 F3 (NEOWISE) reaches its closest approach to Earth on Wednesday. The comet will be 64 million miles away at its nearest. Comet NEOWISE is reported to be 1.8 magnitude with a tail extending 3 degrees. The Big Dipper can be used to find Comet NEOWISE at nautical twilight. The pointer stars at the end of the bucket have been traditionally used to find Polaris, the North Star, as they point up to it. But in the case of this comet, the pointer stars point down to it. Look for Comet NEOWISE about 15 degrees down the star Mirak, the end star on the Big Dipper’s bucket. The 15% illuminated, crescent Moon sets at 10:38 p.m., Thursday night. Comet NEOWISE will be between the Big Dipper and the Moon before it sets.
After you’ve observed Comet NEOWISE, scan 30 degrees above it for M51, the Whirlpool Galaxy. Located 4 degrees below Alkaid, the last star on the Big Dipper’s handle, M51 is comprised of two interacting galaxies. Its companion galaxy is known as NGC 5195. Discovered by Charles Messier on October 13, 1773, the Whirlpool Galaxy was the first to be classified as a spiral galaxy. NGC 5195 was discovered by Pierre Mechain in 1781. These galaxies are 23 million light-years from Earth, and are best observed through a telescope.