Arcturus, the brightest star in the constellation Botes and one of the brightest stars in the night sky. Arcturus is a giant orange-colored star with a diameter about 25 times that of the sun. The surface temperature of Arcturus is only 7,000 F. (3,870 C.), some 3,000 F. (1,670 C.) less than the sun's surface temperature. Because of its size, however, Arcturus gives off more than 100 times as much light and heat as the sun. Arcturus is approximately 36 light-years from the earth. It has an apparent magnitude of -0.1 and an absolute magnitude of -0.3.
Galaxies got their start nearly 14 billion years ago, with one unimaginably hot, dense and tiny pinpoint. How did we arrive at the universe's sprawling state of galactic affairs today?
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?