This is the Dudley Observatory Skywatch Line for Wednesday, January 15th, and Thursday, January 16th, written by Louis Suarato.
After sunset, look for -4.0 magnitude Venus about 23 degrees above the southwestern horizon. Venus will set at 7:55, Wednesday night. The 66% illuminated, waning gibbous Moon rises at 10:27 p.m. Wednesday, in the constellation Virgo. The bright, first magnitude star, Arcturus, rises with the Moon about 30 degrees to its northeast. Arcturus, also known as Alpha Bootis, is a red giant star in the constellation Bootes, and the brightest star in the northern celestial hemisphere. Arcturus, along with Spica in Virgo, and Denebola, in Leo, form the asterism known as the Spring Triangle. When Cor Caroli, in Canes Venatici is added, the four stars form an asterism known as the Great Diamond. To find Arcturus, follow the arc of the Big Dipper. Mars rises at 4:04 a.m. in the constellation Scorpius.
Asteroids are remnants remaining from the planet forming era about 4.6 billion years ago. Of the 930,749 known asteroids, most are located in an orbit between Mars and Jupiter. This section of our solar system is known as the Asteroid Belt. Asteroids, also called minor planets, or planetoids, differ from comets in composition. Unlike comets, which are made up of ice and dust, Asteroids are comprised of minerals and rock. Once thought to be debris from a planet’s demise, the asteroid belt is now believed to be the beginning of what could have been planets, had it not been for Jupiter’s strong gravitational influences. Jupiter’s gravitational pull is also believed to be a shield protecting Earth from incoming asteroids. A recent study by Kevin Grazier suggests that Jupiter may also be responsible for sending asteroids our way. Grazier collaborated with NASA’s Jet Propulsion Laboratory to develop simulations proving his theory. The website spaceweather.com lists recent and upcoming Earth-asteroid encounters. According to this website, as of 1/12/2020, there were 2,018 Potentially Hazardous Asteroids (PHA’s). A chart is provided by the webpage giving the name, date of closest encounter, distance, velocity, and diameter of the PHA.