This is the Dudley Observatory Skywatch Line for Wednesday, June 17th, and Thursday, June 18th, written by Louis Suarato.
The 11% illuminated, waning crescent Moon sets at 5:04 p.m., Wednesday. It will rise as a trimmer 8% illuminated Moon at 3:02 Wednesday morning, approximately 11 degrees above Venus. Friday morning, the 1% illuminated Moon may occult 8% illuminated Venus, depending on your location. You will require a clear east-southeastern horizon to see the Moon and Venus paired up so closely. Begin to look at moonrise, which will occur around 6 minutes past 3 in the morning. Jupiter rises at 10:18 Wednesday night, followed by Saturn 8 minutes later. Mars rises at 1:05 a.m., Thursday. Mercury is stationary at 4 p.m. Wednesday, and begins its retrograde motion. The innermost planet will be 10 degrees above the horizon after sunset, and will be below the horizon in one hour.
June 17 is the birth date of astronomer William Parsons. Born in 1800. Parsons discovered and named the Crab Nebula. Parsons also built a 72 inch telescope named Leviathan in 1845, the largest in the world at the time. The Leviathan telescope was surpassed by the 100 inch Hooker telescope in 1917. The Crab Nebula, also known as M1, was discovered in 1840. This supernova remnant in the constellation Taurus dates back to records by Chinese astronomers of a supernova that occurred in 1054 AD. Is estimated to be 6,500 light-years away in the Perseus arm of the Milky Way. This supernova is expanding at 930 miles per second, or 0.5% the speed of light. At the center of the nebula is the Crab Pulsar. Discovered in the 1960’s by Franco Pacini, it emits pulsars once every 33 milliseconds. Look for the Crab Nebula in this summer’s pre-dawn sky to the lower left of Taurus’ brightest star, Aldebaran.
June 18 is the anniversary of another supernova. In 1918, Discovered by Zygmunt Laskowski, for months it was the brightest star in the sky, at magnitude -0.5, and the brightest nova in the era of the telescope. Nova Aquila was estimated to be about 784 to 839 light-years away. In its place, is now an 11th magnitude binary star system.