For thousands of years the human race has looked to the night sky and wondered if there were other civilizations in the universe. All of the stars we see, which is only a limited number compared to all of the stars in the universe, are suns just like our sun. Actually some of the stars are much larger than our sun, others are smaller. But could they have planets orbiting them just like the planets in our solar system orbit our sun?
Consider these mind-blowing estimates: the Milky Way galaxy, of which our solar system is a member, is estimated to contain 200 to 400 billion stars. And it is estimated that there may be 100 to 200 billion galaxies in the universe. The odds are pretty good that other planets are out there. And there could be life on some of those planets.
A few years ago the Kepler Space Telescope was put into space to look for planets orbiting distant stars. This telescope is looking at 150,000 stars in a part of the sky containing the constellations Cygnus and Lyra. The mission is designed to measure a dip in brightness in these stars, a result of a planet orbiting the star and passing between the star and the telescope.
This is a drawing of the Keppler Space Telescope. Courtesy of NASA.
Just because there is a dimming of the star when the planet makes a "transit" is no guarantee of an actual planet. Kepler needs three such observations of dimming, plus confirmation of these observations by the Spitzer Space Telescope and ground-based telescopes.
So far Kepler has discovered 28 confirmed planets and 1235 candidate planets. The latest news is huge. Kepler-22b (not a very cool name) is in the "habitable zone" of it's parent star, about 600 light years from Earth. This is the zone where it is not too hot or too cold but just right for water to be present. (Earth is the habitable zone planet in our solar system, fortunately for us!)
Kepler-22b is larger than Earth and orbits its star every 290 days. The host star is the same type as our Sun, a G-type star, but is slightly smaller and cooler.
The photo at the top of this blog is an artist's rendering of what the planet may look like. Astronomers don't know if it even has a surface. Perhaps it is all gas like Jupiter, Saturn, Uranus, and Neptune in our solar system. Or perhaps it has a solid surface like Mercury, Venus, Earth and Mars.
To read more about the exciting Kepler mission and their discoveries of planets beyond our solar system, go to their home page HERE.
The orbit of Kepler-22b around its central star compared to our solar system and the orbits of the first four planets closest to the Sun. Note that Kepler-22b orbits its star at approximately the same distance as Earth orbits the Sun. Courtesy of NASA.