In the 1950s, many astronomers began endorsing the theory that our solar system was the result of an extremely close encounter between our sun and another star that accidently wandered into our neighborhood. While the two stars did not physically collide they were thought to have come close enough that a cloud of debris was torn away from the sun which later condensed to form our planetary system. Although our scientists were well aware that our universe contains large numbers of other galaxies each containing incredible numbers of stars, as late as 1995 mankind’s egocentric nature still convinced many of us that our sun might be, if not the only one, at least one of the very few stars which have planets circling it. In that year, astronomers Michel Mayor and Didier Queloz at the University of Geneva in Switzerland spotted a star in their telescope that appeared to have an absolutely miniscule wobble in its motion through space. While they could not see it, the scientists measuring instruments indicated that this small wobble was caused by a planet that was gravitationally tugging on the star as it circled it. Mankind suddenly realized that ours is not the only planetary system in the universe – there was now at least one other one out there. This discovery of the first “exoplanet” orbiting another star triggered a huge wave of excitement among the world’s astronomers.
Astronomers started looking for more exoplanets, and more exoplanets they quickly found! By the year 2000 astronomers had discovered 40 other such worlds, and by 2010, this number had grown to almost 500, with some stars having families of planets similar to our own solar system. At first, the only planets that could be found were giant gas planets (like our own Jupiter or larger) simply because they produced larger tugging effects on their home stars that were more detectable. As these new “planet hunters” (as they were now whimsically labeled by the news media) improved their detection techniques they rapidly began finding smaller and smaller exoplanets that produced even smaller but still detectable tugging effects. In the last few years the planet hunters have started finding “super-earths” that, in some cases, are only about two or three times larger than earth, with some possibly orbiting in their home star’s “habitable zones” where water and life friendly surface conditions may exist (Figure 1).
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| Fig 1. |
Until the spring of 2009, the biggest obstacle to finding small earth-like planets circling other stars was that all of our telescopes were earth-bound which forced us to deal with a dirty and turbulent atmosphere that made it difficult to see the really small stellar wobbles produced by the smaller exoplanets. On March 6 of 2009, this all changed when NASA launched (Figure 2) the first space telescope that would be totally dedicated to detecting exoplanets. This Kepler mission (named after a famous 17th century mathematician and astronomer) started using a new method for detecting exoplanets that was even more sensitive than searching for wobbling stars. Astronomers now began looking for extremely small reductions in the total light coming from a star that occurs when an exoplanet moves in front of it and blocks some of its light making it appear slightly dimmer. This effect is similar (but much smaller) to what happens when the moon moves in front of and “eclipses” our sun. Because astronomers now did not have to deal with the interference of the atmosphere they could actually see reductions in a star’s light as small as 1/100 of 1 percent that would indicate the presence of exoplanets as small or smaller than our earth.
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| Fig 2. |
The Kepler telescope, in just two short years, has now made the “explosion” of exoplanet discoveries made earlier by ground-based telescopes look like the wimpy “pop” of a small firecracker! As of February, 2011, Kepler (Figure 3) has discovered a total of 1,235 possible new exoplanets. However, since NASA currently has Kepler only looking at one very small sector of the sky that is only about 1/400 of the total sky area that is visible from earth, it is quite likely that the 1,235 exoplanets so far detected by Kepler might be a gross under-estimate of the total numbers that might be detectable if Kepler were able to look at the total area of the sky! Thus, exoplanets may be as common as “grains of sand in, if not all, at least many of the earth’s beaches”! Of course, If our own solar system is typical, only one out of 9 of these planets may be life friendly, at least for our familiar carbon-based form of life.
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| Fig 3. |
However, at the end of the 20th century, the astrobiologists had also started making other even more startling discoveries that now suggests that the form of life (based on the carbon atom and water) that exists on earth may not be the only form of life that can occur in the universe. Our scientists have now discovered that life was actually able to first originate on our planet almost four billion years ago when our environment was so hot and hostile that no known forms of living critters were believed to be possible. The discovery of these “extremophiles” (which scientists call “lovers of extreme environments”), whose descendents are still alive today and thriving all over our world, now suggests that life may be far more flexible and resilient than previously thought possible and might easily evolve on other planets that have environments that are totally different from those found on earth. Other exotic forms of life that are based on completely different chemistries from ours may be able to evolve on other worlds in the universe and may actually outnumber our own carbon-based form of life.
Thus, with the beginning of the new 21st century our scientists, while not yet finding any definitive evidence for the existence of extraterrestrial life (life on other worlds), may be close to discovering that such alien life is far more common out there than we would have dared imagine just a few short years ago. The incredible new discoveries of our “planet hunting” astrobiologists will definitely make the remainder of the 21st century a very exciting time for our scientists as well as a “profound eye-opener” for all the rest of us.
Authored by Jerry Cranford - NUP Author
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Figure 1 – Shows an artist’s drawing of a small exoplanet that some astronomers now believe could be inhabited by carbon- based life similar to ours. This planet is one of 6 exoplanets that orbits a small red dwarf star (called Gliese 581) that is only 20 light years from us or 117,313,920,000,000 miles away. (Image credit: ESO)
Figure 2 – Shows the liftoff of the NASA Delta rocket carrying the Kepler planet hunting space telescope into high earth orbit. (Image credit: NASA/JPL)
Figure 3 – Shows an artist’s drawing of the Kepler telescope hard at work in space looking for evidence of exoplanets. (Image credit: NASA/JPL)
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