This month look for the star Deneb, the brightest star of the constellation of Cygnus the Swan. The word Deneb is Arabic for tail, referring to the fact that the star represents the swan’s tail. Deneb is the 19th brightest star in the sky. It, along with the stars Vega and Altair form the Summer Triangle. The Summer Triangle is an asterism and not a constellation. The Summer Triangle passes directly overhead at 9:00 PM in early September.

Deneb is somewhere between 1,600 and 2,600 light years away. This makes Deneb the most distant star visible without a telescope. The reason that we can see it from so far away is that it is a massive star. It has 20 times the mass of the Sun and a diameter 200 times greater than our Sun’s diameter. If Deneb were to replace our Sun, it would fill the orbit of Earth. Deneb’s large mass makes it 250,000 times brighter than the Sun. Deneb has a surface temperature of 16,000 degrees Fahrenheit, or white hot. For Earth to maintain a mild climate while in orbit around Deneb, Earth would have to orbit Deneb at a distance ten times greater than the distance between Pluto and the Sun. The supergiant Deneb is so hot that it is blowing material off of its surface at a rate a thousand times faster than the Sun. This large mass loss is not sufficient, however, to reduce Deneb’s mass down to safe levels before its too late. Within a few million years, Deneb will end its life in a supernova explosion.     

Deneb appears directly overhead at 9:30 PM in early September and at 8:30 PM by the end of the month. Look for Deneb as the faintest and most northeast member of the Summer Triangle.