This is the Dudley Observatory Skywatch Line for Wednesday, March 28th, and Thursday, March 29th, written by Louis Suarato.
The 91% illuminated, waxing gibbous Moon rises at 4:22 p.m. Wednesday. As the sky darkens, look for Leo’s brightest star, Regulus about 5 degrees to the upper right of the Moon. Venus sets at 8:50 p.m., 77% illuminated. Thursday, Venus and Uranus will be less than a degree apart. Use binoculars in your search for Uranus to the lower right of Venus. Jupiter rises at 10:58 p.m. in Libra. Mars and Saturn rise in Sagittarius at 2:33 and 2:36 a.m., 2 degrees apart. There are two globular clusters 1 to 2 degrees to the lower right of each planet. To the lower right of Mars is the globular cluster M28. Discovered by Charles Messier on July 17, 1764, M28 is 17,900 light-years from Earth, and its stars are estimated to be about 12 billion years old. M28 has a diameter of 60 light-years, and contains at least 50,000 stars. The Great Sagittarius Cluster, also known as M22, is to the lower right of Saturn. When Abraham Ihle found this globular cluster on August 26, 1665 while observing Saturn, it was one of the first to be discovered. At magnitude 5.10, it is one of the brightest globular clusters, and at the distance of 10,600 light-years, M22 is one of the nearest. The estimated 83,000 stars within the Great Sagittarius Cluster are also estimated to be about 12 billion years old.
March 29th is the anniversary of Heinrich Wilhelm Olbers’ discovery of asteroid 4 Vesta. When Olbers observed 4 Vesta for the first time in 1807, it was the only asteroid visible to the naked eye. With a diameter of 326 miles, 4 Vesta is one of the largest objects in the asteroid belt. 4 Vesta is second only to dwarf-planet Ceres in mass, accounting for 9% of the total mass of all asteroids. 4 Vesta formed about 1 to 2 million years after the solar system, around 4.5 billion years ago. Look for 4 Vesta about 10 degrees to the upper right of Mars, and 2 degrees above star cluster M23.