Fall officially starts Thursday, Sept. 22, at 7:21 a.m. Mountain Standard Time. That’s when the sun shines directly on the equator as it travels from the northern part of the sky into the southern. If we were on the equator, the sun would be overhead at noon local time.
Thursday is also a good time to enjoy Cygnus the Swan which will be almost directly north and about 70-75 degrees above the northern horizon at 8:30 p.m. Because the six brightest stars of Cygnus form a cross with the top of the cross pointing northeast and the bottom of the cross pointing southwest, Cygnus is commonly called the Northern Cross.
Cygnus is supposed to represent a Swan flying south along the Milky Way. The brightest star in Cygnus, Deneb, is at the top of the cross. However, Deneb is actually the tail of the Swan, because the “Cross” and the “Swan” point in different directions. Deneb is the Arabic word for tail.
Deneb is one of my favorite stars. It is the 19th-brightest star in the sky and is one of the most luminous stars in the entire galaxy. Deneb is so far away its exact distance is unknown, but it is felt to be around 1,425 light years with Deneb having a luminosity of nearly 60,000 times that of the sun. Deneb has a diameter more than 100 times that of the sun.
