Canis Major, a constellation of the winter sky. Sirius, the brightest star in the sky, is in this constellation. Canis Major rises in the east after Orion, the hunter. It is slightly below Orion, and appears near the southern horizon in the United States. A line through the three bright stars of Orion's belt leads to Sirius. In classical mythology, Canis Major (great dog) was one of the hunting dogs of Orion, and the constellation is supposed to look like a dog.
It's tough to wrap your mind around a time when the Earth wasn't here. So how do Earth and the rest of the planets out there get their start in the universe?
A billion years ago, the moon stopped being geologically active. But that's not to say that the moon is doing nothing for us. Let's find out why we owe our moon some thank-yous.