Exploration Talks

 The closest star to Earth is a triple-star system called Alpha Centauri.   The two main stars are Alpha Centauri A and Alpha Centauri B, which form a binary pair. They are about 4.35 light-years from Earth, according to NASA (opens in new tab). The third star is called Proxima Centauri or Alpha Centauri C, and it is about 4.25 light-years from Earth, making it the closest star other than the sun. According to NASA, Alpha Centauri A and B are on average about 23 astronomical units (AU) from each other — a little more than the distance between the sun and Uranus. (An astronomical unit is the average distance between Earth and the sun, which equals 92,955,807 miles or 149,597,870 kilometers.) The closest the two stars ever come to each other is 11 astronomical units, according to NASA (opens in new tab)   To the naked eye, the Alpha Centauri A and B shine as one, making them the third brightest "star" in our night sky. The two separate stars can be seen through a small...