Astronomy Journal Entry
Earth-like Exoplanets Found (May 4, 2009)
Artist's impression of an Earth-like planet orbiting a red dwarf star called Gliese 581. European Southern Observatory.
Astronomers discovered two exoplanets with Earth-like characteristics orbiting the red dwarf star Gliese 581, found within the constellation Libra. One is a rocky planet a bit bigger than Earth. The other is a gas giant within its star's habitable zone, where temperatures suitable for liquid water to form.
The smaller of the two planets is called Gliese 581 e. It's about twice as massive as Earth, making it the tiniest and closest to Earth-size of the 350 or so exoplanets found so far. It probably has a rocky surface but orbits too close to its star and is too hot for water to exist. The planet completes its orbit in about three Earth-days. The larger exoplanet, Gliese 581 d, has seven times the mass of Earth. Although it's too big to be a rocky planet, it's the right distance from its star for water to form.
The discovery raises the hope of finding other exoplanets that are both the right size and the right distance from their stars to have water and support life.
Gliese 581 is only 20 light years from Earth, making it one of the 100 closest stars to our home planet. A light year is the distance light travels in one year or about six trillion miles (ten trillion km).
