Searching for how many planets are in space calls for time; if our own Galaxy - the Milky Way - is +- 100,000 Light Years in diameter. We also need better understanding.
According to a NASA's Jet Propulsion Laboratory report, June 9-2009 'more than 350 extra solar planets have been detected, but most are gas planets without a solid surface.'
Only this year, 2009 in March, the $500 Million mission set off from Earth to discover 'Space'. It is reported as having the largest camera ever to be launched into space, using extreme precision Kepler Optics, and to take about 3 - 4 years.
From space, it will slowly move away from the earth and orbit the sun by itself. It is from here, it is looking for more planets in one section of space. NASA's hopes are not without belief that there have to be more, to go this far.
Kepler's sophisticated high resolution cameras, acting like a camcorder; will look at a fixed position of the sky. It is designed to be sent into space by the Delta 11 (2) Rocket, to obit as the 'Kepler Space Ship' in the Earth's Trailing Orbit. Astronomers call this a Heliocentric Orbit, which means a sun centered orbit.
By September 22-2009 Kepler was 18 million km. (11 million miles) from Earth. That's 46 x the distance of the Moon from Earth, as it scans out Milky Way. The Science data from NASA's Ames Research Center is being analyzed to date.
The estimated size of the Universe is + - 93 Billion Light Years; so until we ourselves have conquered traveling at the fundamental constant of the Speed of Light at 300,000 km. per second, we have yet to honestly know how many planets are in space.
The Kepler Camera will no doubt do it's best with the speed of light this camera can operate in, in searching within it's given field of space. So we'll live in hope with NASA, despite all the controversy. That it is better to spend $500 Million in Peace than in War, and come up with something other than the selfish thought that we - as earthlings - are the only habitable planet in the Universe.
Johannes Kepler, the 17th Century Astronomer who discovered the Laws of Planetary Motion, would be over the moon to see he is remembered! Our greatest 20th Century Cosmologist, Dr. Carl Sagan at NASA, sadly returned to 'his stars' in 1996 - too soon - after taking many into space in his 'Ship of the Imagination', in the great TV documentary series, COSMOS, in the 1970's.
As the USA government helped fund SETI - the 'Search for Extraterrestrial Intelligence' in the beginning - NASA must still believe enough to search for other habitable planets in space. Plus, they would hardly have agreed to sending the Golden Disks of 'Greetings from the Children of Earth' in Voyager 1-2, if they didn't (when Dr. Carl Sagan was with NASA.)
Our techniques via satellite imagery, and telescopes, have found many classified as 'planets'. Despite how these are detected, up to19 Oct. 2009, 403 planets are in count in the Paris Observatory; 341 planetary systems, and 42 multiple planet systems. These statics are according to the Extra solar Planets Encyclopedia. http://exoplanet.eu/catalog-all.php?&munit=&runit=&punit=&mode=-7&more=
We cannot live like a fish in water - who die out of it - yet an environment could be a very different medium to our own livable standards, when measured on another planet. We seem to seek out planets as if psychologically they should appear 'habitable' only within reasonable conditions which apply to ourselves.