Scrutinizing The Habitable Zone

This week the NASA Kepler telescope team announced the discovery of another 715 “exoplanets” outside our solar system — all of which are in their own multi-planet solar systems. The announcement represents another giant leap forward in our understanding of other solar systems, and how commonplace multi-planet systems are.

The Kepler space telescope was focused on finding instances of “transits,” when light from a faraway sun drops slightly in brightness because a planet has crossed in front of the sun. The size of the variation in light allows scientists to calculate the size of the planet moving across the face of the sun. Most of the newly discovered planets — about 95 percent — are smaller than Neptune, which is four times the size of Earth. The size of the planets is of interest to scientists because it is believed that life is more likely on smaller planets than on Jupiter- and Saturn-like gas giants, with their enormous storms and atmospheres that feature crushing pressures.

Four of the newfound planets are less than 2.5 times the radius of Earth and orbit their suns in the so-called “habitable zone,” where water could be free flowing without being boiled away or frozen forever. The term “habitable zone” may be a misnomer, because we just don’t know yet whether life of some kind exists on, say, Jupiter’s moon Europa — and we won’t know for sure without actually exploring there. We do know, however, that life exists in the “habitable zone” in our solar system, and therefore it makes sense to try to determine whether life might exist in a planet in a similar position in its solar system. All of this effort, of course, is ultimately geared toward trying to make a truly game-changing discovery of some other intelligent life form in the universe.

If you grow weary of the tribal mire of domestic and global human affairs, where progress is rare and and halting and the same disputes and controversies will seemingly never end, you would do well to consider the extraordinary advances in science and technology that we have witnessed in the last few decades. The discoveries of the Kepler telescope team say a lot — all of it good — about what humans are capable of achieving.

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Alpha Centauri’s Earth-Sized Planet

Science continues to achieve amazing advances in our ability to detect, measure, and analyze planets orbiting stars far outside our solar system.

So far, scientists have discovered and confirmed the existence of more than 800 planets.  Most of the planets, however, are huge gas giants, like Jupiter or Saturn in our solar system.  The latest advance in detection capabilities came this week, when scientists announced that they have detected the lightest planet to orbit a Sun-like star — and the star just happens to be Alpha Centauri, a weird, triple-star system that is the Sun’s nearest galactic neighbor.

Alpha Centauri, for those who fell asleep during astronomy class, is a mere 4.3 light years away.  Of course, one light year is 6 trillion (6,000,000,000,000) miles away, but who’s counting?  The planet scientists have detected is about the mass of our good Earth.

Before you start worrying that little green men might appear on your doorstep tonight, take a deep breath:  the Earth-sized planet is closer to Alpha Centauri B than Mercury is to the Sun, so it’s probably not conducive to life.  Still, the discovery is remarkable.  In the not too distant future, scientists will use this detection technology to find a planet about the size and mass of Earth, orbiting a star a lot like Sol, at a distance that would suggest that it is likely to be temperate.  What will that mean?  My guess is that we will train every radio telescope and sensory device we have in the direction of that planet, listen as hard as we can, and hope.