Exoplanets: "This illustration depicts stars with more than one planet. The planets eclipse or
transit their host star from the vantage point of the observer, an angle called edge-on," National Geographic says.
Launched in 2009, NASA's $591 million Kepler Space Telescope has now discovered most of the planets orbiting nearby stars. "We've hit the motherlode; we've got a veritable exoplanet bonanza," says Kepler co-leader Jack Lissauer of NASA's Ames Research Center in Moffett Field, California.
The newly announced exoplanets reinforce the view that most solar systems around sunlike stars have smaller-size planets. Most of those planets range in width from Earth-size (on the smaller side) to Neptune-size (on the larger). That's quite a change from the Jupiter-size planets that were often spotted orbiting nearby stars during the early planet searches that started in 1995."Nature likes to make small planets," says the Massachusetts Institute of Technology's Sara Seager, who was not part of the discovery team but commented on the findings at a Wednesday NASA briefing.
Four of the newly discovered planets orbit around their stars in "habitable zones"—regions where temperatures are just right for oceans, which bring with them the possibility of life. But the four planets are all a little more than twice the width of Earth, which may make their atmospheres unfriendly to life as we know it. (See: "Earth-Size Planets Come in Two Flavors.")
The newly discovered 715 planets orbit in solar systems around 305 stars, mostly ones the size of the sun or smaller. Many of the planets orbit in what is beginning to be seen as a more typical solar system, in which the largest planet is Neptune-size and a bevy of smaller Earth-size planets orbit close-in to their star and close to one another. "These new Kepler results are very helpful in filling out the statistics of solar systems," says Princeton's Adam Burrows, who was not part of the discovery team. "The goal is to see how typical is our own solar system, and ones unlike it."
Our solar system might be typical in some ways and atypical in others, I suspect, just as there are variations among humans and within nature on our planet we call home. This raises the question on why there should not be symmetry or statistical variations in our universe, known or unknown. If there are planets that can support life, human or otherwise, it would confirm decades of science fiction and popular TV shows and films. This would not only be exciting, but would also have the added benefit of placing humans in their proper place.
You can read more of this article at [NatGeo]