Gliese 581g, an earth-like planet found orbiting a red dwarf star only 20 light-years away back in 2010, has been widely considered to be, of the 600 or so extrasolar planets discovered so far, one of the most likely to harbor life, since it is only two-and-a-half times the size of earth and right in the middle of its' star's so-called 'habitable zone'. However, since shortly after its discovery, there have been questions as to whether or not it truly exists. Being too far away to image directly, the only way it's existence can be inferred is through its' effects on its' parent sun, and such effects are at the very limit of scientific observability. Other scientific teams, most notable a Swiss team only several months after the initial discovery of Gliese 581g, have been unable to find conclusive evidence of its existence, and the battle has gone back and forth in the four years since then.
Now, fresh evidence has cast further doubt on the existence of Gliese 581g. In an article published in the June issue of Science, Stephane Urdy, an astronomer with the University of Geneva, states that the data that was interpreted as suggesting the existence of Gliese 581g may have been due to sunspots and solar flares that influenced the changing magnetic activity of its' parent star, Gliese 581, rather than the existence of an actual planet. While disappointing, this again serves to point out how difficult it is to detect extrasolar planets, and the need to avoid jumping to conclusions in our desire to discover new worlds that could have life on them, possible even intelligent life. Hopefully, in the next ten or twenty years, with the launching of new and bigger space telescopes, such as the Webb, and the building of even larger ground-based telescopes, such as the 30-meter telescope being built in Europe, we may soon be in a position where we will be able to observe these worlds directly, and no longer will need to guess at their existence. Until then, perhaps caution should be the watchword.