It turns out that the nearest exoplanet is right next door. Of course, the neighborhood is kind of on the large side. In this case, next door is 4.2 light years ago, orbiting Proxima Centauri, the closest star, not counting the sun. Proxima Centauri is a very small star, class M, and puts out very little light compared to what we’re used to. This planet (Proxima b) is orbiting in the habitable zone, the so-called goldilocks zone, where liquid water would be possible.
This makes it theoretically possible that life could evolve there. But this is unlikely since the amount of X-ray or Gamma-ray radiation from the star is about 100 of the amount we get, which would break down DNA very quickly. Any life would have to store genetic information in a very robust chemical. Because class M stars are so small, the habitable zone is also very small. Proxima b’s year is about 11.2 of our days long; it’s orbit would be well inside Mercury’s orbit.
Popular Mechanics has a good article on the planet.
A star inside another star. Also, planet hunting.
It looks like every star in the Milky Way has at least one planet. By looking at the exoplanets we’ve found so far, and taking into account factors like distance from the star, temperature, density, etc., it looks like there may be as many as 100,000,000 planets that may support complex life. We’re not talking about alien civilizations here. Just something more than a microbe. That’s only for our galaxy. Given the hundreds of billions of galaxies out there, we’re very likely not alone.
NASA’s Kepler satellite has found an Earth size planet in its star’s Goldilocks Zone. This is the first habitable zone Earth size planet found so far; all the previous ones were much larger than Earth. Kepler-186f orbits a star about 500 light years away in the constellation Cygnus. The star (Kepler-186) is an M class red dwarf. The planet is on the outside of the habitable zone, so it’s probably fairly cold, but that really depends on the atmosphere. So far all we really know about the planet is that it’s just a little larger than Earth, and is probably rocky (not a gas giant). Due to its orbit close to the star, it probably has a long day, as long as our week or month.
Kepler-186f orbital characteristics
Update 21 April 2014
This link on How close are we to finding extraterrestrial life? has some good notes on the types of planets Kepler has found and how new telescopes will help the search.
Not impossibly distant from us, but from the host star. HD 106906 b is in the constellation Crux. The planet orbits at a distance of 650 AU, or 97 billion kilometers (more than 20 times the distance from the Sun to Neptune, and is 11 times more massive than Jupiter. The system is thought to be only 13 million years old, very young. Our current theory of how solar systems form will have to change because of this discovery. A planet should not be able to form that far away from the star. If it is a binary star instead of a planet, then it isn’t massive enough. Our understanding of binary stars is that the stars should have relatively close masses, about 10:1. This is over 100:1.
There is a petition to name the planet Gallifrey, after the home world of Doctor Who, but the IAU doesn’t accept popular names for exoplanets.