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Other Worlds, Other Stars

We used to be able to count the number of known planets on the fingers of both hands. Then astronomers developed ways to find worlds around other stars. We are discovering new ones all the time. Our solar system isn’t alone in the galaxy anymore.

We haven’t found a planetary system that exactly matches our Sun’s collection of planets, moons, asteroids, and comets. The first extrasolar worlds we discovered are the size of Jupiter. The search continues for even smaller, more Earthlike planets orbiting other stars.

47 Ursae Majoris: 47 Ursae Majoris is a star similar to our Sun. Like the Sun, it has two giant planets. Both are closer to their sun than Jupiter and Saturn are to our Sun, but are probably too cold to support life.

51 Pegasi b: Discovered in 1995, this was the first planet found around a star like our Sun. This planet is large, like Jupiter, but its distance from its sun is less than Mercury’s distance from our Sun.

55 Cancri A: None of the four planets of 55 Cancri A orbit in the star’s habitable zone, where liquid water can exist on the surface of a planet.

Gamma Cephei A: One large planet has been found orbiting the star Gamma Cephei A. Gamma Cephei is a two-star system, and so two suns would appear in the planet’s sky.

Gliese 876: Dim and red, Gliese 876 is one of the closest stars to our sun known to have planets. The inner planet is probably only a little larger than Earth, but it orbits very close to its sun and may be too hot to support life.

PSR 1257+12: The very first planets discovered around another star orbit a pulsar, PSR 1257+12. A pulsar is the core of an exploded star. We do not know if the planets survived the explosion or formed afterwards.

Upsilon Andromedae A: Three planets have been found around the Sun-like star Upsilon Andromedae A. The middle planet is in the star’s habitable zone.