Astronomers are actively searching for Earth-like planets outside of our solar system - or as they say, exoplanets. Most of the planets they have found so far are enormous, at least the size of Jupiter. It's much more difficult to find planets as small as Earth. Now, scientists believe that 6 percent of red dwarf stars have Earth-sized planets located at the right distance from the star to be potentially habitable.
Our Milky Way Galaxy may be home to approximately two billion Earth-like planets. This is based on a new study and initial data from NASA's Kepler space telescope. Based on Kepler's findings so far, the studies are up to 2.7 percent of all sun like stars in the Milky Way host so-called Earth like worlds. As of this February, Kepler has confirmed 15 new planets and found an additional 1,235 planet candidates, including a small planet outside of our solar system. Kepler will collect data for a minimum of three and a half years and plans to undertake a more complete census at a later date.
What I have found in my research is that the closest Earth-like planet astronomers have reported may be only 13 light years away - or approximately 77 trillion miles. They have not identified it yet, but feel it should be there based on the teams' study of red dwarf stars. Most of us have heard of Gilese 581, a red dwarf star in the constellation Libra that lies about 20.5 light years from Earth. The European Southern Observatory (ESO) telescope in Chile has discovered Gilese 581d, a planet they speculate to have a rocky core, an icy layer, and a liquid ocean at the surface with an atmosphere. At this stage they can only speculate but it is possible. Gilese 581e is another planet looking much like Earth, except that it is very hot because it so close to its host star.
NASA and the scientists working on this project favor Kepler-22b which was discovered about 600 light years from us, in another solar system. They view this planet as having the best chances of life because of the striking similarities to Earth. Its surface is a comfortable 72F and the star it orbits can almost be a twin of our sun. Although it is 2.4 times bigger than Earth, scientists suspect it probably has water and land making it a great target for life. Now scientists have found other planets in in the Kepler-22 group which makes this a study of 3 or 4 planets that may all be Earth-like.
So how do scientists find these planets? That's a great question - there are four ways:
The first is called the "radial velocity method": This is when stars are pulled back and forth by the gravitational pull of the planet. This allows them to measure the shift in the light frequency.
Another method is "positional astronomy": This is when they take a measurement of the tiny shift in a star's location on the sky which is caused by the gravitational pull of a planet. They can determine mass and orbit as well.
The "transit method": Scientists have found that a planet blocks out a small portion of the star's light when it passes directly between a star and the observer. They will watch it to confirm the fluctuations in the star's light. This means a planet is orbiting that star.
Last is the "gravitational microlensing" method: This comes from Einstein's thoughts regarding his theory of relativity. I like this ~ gravity bends space. The planet's gravity will act like a lens for a short time to focus light from a star. This works well with more distant stars. It seems to warp space to cause a noticeable increase in brightness and a change in position of the star.
I never said it's easy to find planets outside of our solar system. Most of them are very far away, but recently astronomers have found a planet that orbits a star called Alpha Centauri B, which is our closest star about 4 light years away or 23.5 trillion miles. It is a rocky planet but may be too hot to sustain life. Any time we can measure the distance in space using miles (even if it is trillions) this would be termed as being in our neighborhood.
There's a plan to search in more depth for Earth-like planets: http://www.dailygalaxy.com/my_weblog/2013/04/kepler-mission-20-to-launch-in-2017-thousands-of-neigboring-earth-like-alien-planets-to-be-identifie.html
My references include: NASA online, Daily Planet, StarDate.org, and dailygalaxy.com.
