From here on Earth, the big dog among the stars is Sirius, the brightest star in the night sky. It’s the leading light of Canis Major, the big dog, so it’s also known as the Dog Star. And it really is a bright star — a couple of dozen times brighter than the Sun. Yet it looks so bright mainly because it’s close — less than nine light-years away. In fact, if you lined up all the stars in the classical outline of Canis Major at the same distance, Sirius would look like a candle in a field of searchlights. The constellation is home to some truly impressive stars. And perhaps the most impressive of all is Aludra, at the tip of the dog’s tail. The details are a bit blurry, because there’s a wide range in measurements of the star’s distance. Even so, we know that Aludra is a blue supergiant. It’s tens of thousands of times brighter than than Sun. Its also is dozens of times wider than the Sun, and 15 to 20 times heavier. We also know that Aludra is quite young, but it’s already nearing the e
