Appearances can be deceiving — especially among the stars. For an example, look at the stars that mark the points of the Summer Triangle, which is in the east and northeast at nightfall. The brightest point is Vega, one of the brightest stars in the entire night sky. Yet Vega looks so bright in large part because it’s close by — only about 25 light-years away. The true luminary of the Summer Triangle is Deneb, which stands to the lower left of Vega during the evening hours. It’s probably a thousand times brighter than Vega, and tens of thousands of times brighter than the Sun. Astronomers are a bit uncertain of its true brightness because estimates of its distance vary by hundreds of light-years. Deneb is a supergiant. Its diameter is probably a couple of hundred times that of the Sun. If it took the Sun’s place in our solar system, the star would swallow all three of the innermost planets — including Earth. Deneb is also a couple of dozen times as massive as the Sun. That means it bur
