According to the Extrasolar Planets Encyclopedia, a database of new alien worlds compiled by astrobiologist Jean Schneider of the Paris-Meudon Observatory, the total number of alien worlds that have been discovered since 1992, now stands at over 700.
In 1992, astronomers discovered two alien worlds orbiting a neutron star about 1000 light-years from Earth. The first discovery of a planet orbiting a main sequence star, that is, a star in the prime of its life cycle like our Sun, was in 1995.
The rapid increase in new extrasolar planet discovery in the last few years has opened a new and exciting chapter in our knowledge of the Universe and has helped to renew hope among SETI enthusiasts that we may encounter alien life in the next few decades.
The total number of extrasolar alien planets, according to Space.com, reached 500 in November 2010, and 600 just two months ago when scientists announced an astounding harvest of new finds, 50 planets at once, including a single planet with conditions which seem right for alien life.
Some SETI enthusiasts are so impressed with the rate at which new planets with conditions suitable for life are being found that soon after astronomers announced discovery of 16 new "super-Earths" (planets with rocky surfaces like the Earth on which life can grow) among the set of 50 new exoplanets discovered, an astrophysicist at the SETI institute Gerald Harp, asserted that with new information available to astronomers on distribution of Earth-like planets around stars, they may only have to search about 100,000 stars before finding signs of alien life.
One of the most promising "super-Earths" discovered was HD 85512b located in its star's "habitable zone" where temperatures are just right for liquid water to be formed. Discovery of such planets as HD 85512b spurred renewed interest in search for extraterrestrial life and SETI's radio telescopes in Mountain View, California, that had been shut down were revived, now focusing search on the new super-Earths. Unfortunately, the prime candidate HD 85512b, was too far south for SETI telescopes to focus on. But Jill Tarter, director of the Center for SETI Research, said:
"When the array [of telescopes] is again operational we will go back to our exploration of exoplanets...We will, however, add those exoplanets reported by [ESO] that are visible to our list of targets. The more planets the better!"
Gerald Harp expressed optimism that SETI may find first evidence of alien life in the next 15 years:
"…a large proportion of stars are now believed to host Earth-like planets. We now know that perhaps 1 percent of stars have planets where biological life may arise. We also know where some of those planets are...Fortunately for me, I expect to still be actively pursuing research in 15 years, so I will be around when it happens!"
Apart from excitement at perfecting skills for locating planets that may support life, astronomers are also amazed at the variety they have encountered. A very intriguing recent find, according to Space.com, was an alien world orbiting two suns. That is, on this unique planet, two suns rise and set over the horizon and not just one as in our planet Earth.