13 THINGS Look Up! Facts About Stargazing

Just how many stars can we see with the naked eye? The Yale Bright Star Catalog provides the answer: 9,095.

- Joe Rao

Except we can’t see all of them at once because at least half would fall below the horizon. Daylight and haze also limit us. So in fact, the number of stars we can see at night at any given time is around 2,000.

2 The largest star visible with the naked eye is Mu Cephei, a strikingly red star in the constellation Cepheus (the King). If our sun was the size of a softball, Mu, in comparison, would be 437 feet across. The brightest star in the sky is Sirius, or the Dog Star, in the constellation Canis Major. Orbiting it is a white dwarf star known as Pup. Though about the size of Earth, Pupis far denser. On our planet, a teaspoon of its material would weigh 5 tons.

3 The farthest celestial object visible without a telescope is the Andromeda galaxy, 24 quintillion kms away. On a clear night, it appears as a faint elongated patch. When its light began travelling earthward, mastodons and saber-toothed tigers roamed North America. An estimated 1 trillion stars make up Andromeda, more than twice the number in our own Milky Way galaxy.

4 Contrary to popular belief, Galileo did not invent the telescope. The genius behind it was spectacle-maker Hans Lippershey, who applied for the patent in 1608. Telescopes were initially pointed not at the sky, but at the seas—to spy on ships. Galileo first turned a telescope toward the heavens in 1609.