It was just as recent as 1995 that scientists first learned there exists other planets outside our solar system. Before that time, scientists speculated that there might be other planets out there but had no observational proof. Since that first planet was discovered though, astronomers have literally been finding hundreds of new “exo-planets” every year using a new technique in light measurement called Radial Velocity.
The stars in our sky are so bright we would never be able to detect the light from a planet outside our solar system because it’s glow would be just too dim and overwhelmed by the star’s light. So what astronomers learned to do was judge the light emanating from a star and look for changes in the beam. If there was a “wobble” in the star’s light, then it showed us the gravity of a planet enacting a force on the beam of light produced from that star. This technique also allowed scientists to judge the mass of the planet and the approximate distance from the star.
After discovering hundreds of planets in the last 15 years (most Jupiter-sized gas giants and uninhabitable) it was just today, according to a NASA media brief that scientists have found a planet that meets the conditions of the so-called “Goldilocks zone” or conditions that are just right for life. Gliese 581g is the name given to this planet which is slightly larger than Earth, but is the appropriate distance from its’ sun to make life a possibility. This breakthrough suggests that the Milky Way galaxy could be teaming with potentially habitable planets.
In order to be habitable, according to astronomers, an exoplanet must have liquid water and an atmosphere, among other considerations. Habitable doesn’t mean that life exists on the planet, only that the “possibility of life” exists. The exoplanet was discovered orbiting around the star Gliese 581. The star is about 20 light-years away from Earth, within the constellation Libra. The planet is considered a “Class M” celestial body originally coined by Star Trek creator Gene Roddenberry, who used it to describe planets that had Earth-like temperatures and atmospheres in the fictional TV series. Keep in mind that yesterday’s science fiction is todays science fact.