To date, the efforts of astronomers and other scientists (including some citizen scientists) have confirmed the existence of 843 exoplanets in 665 different star systems, including the one right next door to our own. As of January this year, the Kepler mission alone had recorded another 2,321 other unconfirmed exoplanets, with the French Space Agency COROT mission adding another 23 confirmed planets and at least 600 unconfirmed planets to that (as of November 2011).
More planets are being discovered and confirmed all the time, and observations using 'gravitational microlensing' have turned up some incredible results — that each star in the Milky Way Galaxy may have at least one planet.
With all these discoveries, as well as scientists exploring new ideas about where life could exist, the idea of life existing elsewhere is gaining more acceptance in the scientific community.
"I think scientists are very happy having a rational conversation about the likelihood of life out there," said British astronomer Bob Nichol, according to News Daily. "An explosion in the number of planets makes it so much more likely."
New technologies will soon be joining the search for planets and the search for life on those planets.
The Square Kilometer Array (SKA) is an Earth-based radio telescope array scheduled to be operational by 2024. An international consortium, of which Canada is a member, is designing and building SKA. It will be located in both Australia and South Africa, and will have a total collection area of — as the name suggests — one square kilometer, over 100 times the size of any current radio telescope. Astrobiologists plan on using the telescope array to search for the spectrum of amino acids, the basic building blocks of life.
The European Extremely Large Telescope (E-ELT), a 40-metre-class telescope planned for the ESO La Silla Observatory in Chile, will be the world's largest optical telescope when completed. One of the specific missions of the E-ETL will be to find more exoplanets by observing the wobble of stars due to planets orbiting them, but it will also hopefully be able to directly observe larger planets and determine their composition.
All of the current finds and these future efforts certainly brings up the question of whether or not there is intelligent life out there. SKA will be sensitive enough to detect faint extraterrestrial radio signals, should those signal exist. E-ETL may directly observe planets that have the ability to sustain life.
Simply the number of planets we're finding definitely brings some interesting values to the Drake equation.
First introduced in 1961, by astronomer Frank Drake, the equation gives an estimate of the number of civilizations out there that we might be able to communicate with. The equation looks like this:
N = R* x fp x ne x fl x fi x fc x L
Where N is the number of civilizations we could possibly communicate with, R* is the annual rate of star formation in our galaxy, fp is the fraction of star systems with planets, ne the average number of planets that can potentially support life per star that has planets, fl the fraction of those planets that can support life actually developing it, fi the fraction of those planets that develop life going on to develop intelligent life, fc the fraction of those planets that develop intelligent life building technology that can send signals out into space, and L is the length of time that civilizations will release detectable signals into space.
These numbers were all hypothetical when it was first proposed. You could plug whatever numbers you want into it, optimistic or pessimistic, just to see what the result would be.
The Drake equation is still completely hypothetical today, because we'd have difficulty assigning a value to the last three terms. We're not doing too badly for the first three, though. We've had a good idea of the value of the first term since 2006, and these days, we have some very solid numbers coming in for how many star systems have planets, and we're getting some much better ideas about how many of those planets could support life.
As for the middle term, there's no way to be absolutely sure about this one until we actually start detecting evidence of life out there. However, one thing we've learned by exploring our own world is that, if life can exist somewhere, it usually does exist there, even if we don't think it's possible.