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NASA Finds Family of Habitable Planets
coondoggie writes "NASA's star-gazing space telescope continues to find amazing proof that there are tons of habitable planets in space and we have only scratched the surface of what's out there. The space agency said today its Kepler space telescope spotted what it called its first Earth-size planet candidates and its first candidates in what it considers to be the habitable zone, a region where liquid water could exist on a planet's surface. Kepler also found six confirmed planets orbiting a sun-like star, Kepler-11. This is the largest group of transiting planets orbiting a single star yet discovered outside our solar system."
Surveys such as this tend to find lots of large planets close to their stars. It is worth pointing out that this is at least partly because such planets are easier to detect, and does not necessarily mean they are a high proportion of planets in the galaxy.
Kepler detects changes in stellar brightness due to transiting planets. The closer a planet is to its star, the less precise the alignment has to be for us to observe a transit. Also, the closer it is, the faster it orbits, and the more likely we observe a transit in the limited time we're observing that star. This second factor will become less restrictive as the Kepler mission runs for a longer time. (I presume they need at least two, possibly more, transits before they claim a detection.) Large planets will also give a larger, easier to detect change in brightness.
The other major way of detecting planets is spectroscopically: the planet wobbles the star slightly, and we observe the Doppler shift. This favours massive planets (they wobble the star more) and close planets (they wobble the star faster.)
There have I think also been a few cases where clever interferometry has allowed direct imaging of extrasolar planets. I don't know what the selection effects on this are - further away means easier to separate from the star (good) but less bright (bad.)
Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
It's not NASA's fault, the actual press release says nothing of the sort.
The NASA press release described a system of at least 6 larger -than-earth planets, all much closer to their sun than Earth is. Late in the release, they mention that "Kepler will continue conducting science operations until at least November 2012, searching for planets as small as Earth, including those that orbit stars in the habitable zone, where liquid water could exist on the surface of the planet. Since transits of planets in the habitable zone of solar-like stars occur about once a year and require three transits for verification, it is predicted to take at least three years to locate and verify an Earth-size planet. "
Then Michael Cooney appears to have invented from whole cloth the title, "NASA Kepler finds family of habitable, Earth-size planets". I do have to admit that the Slashdot title is pretty close to the Cooney source, but the article is... not even close to what it claims to be its source material.
I suppose the Earth being potentially borderline habitable may have something to do with the apparent lack of evidence of extraterrestrials. A planet that is too friendly to life may not have had the 6+ mass extinctions and rapidly changing environment that helps drive evolution. One that's borderline habitable like ours (assuming the assertion in your link is true) keeping life for as long as it has might be a tremendous fluke.
It's not that hard to understand.
If you can observe a planet with a few different methods, you can reliably calculate it's mass and radius from the size it appears, it's orbital period and inclination, the effect it exerts on the star, and other data points.
Once you have the mass and radius, you can calculate the density, which allows you to speculate on whether it is rocky or gaseous. This in turn opens up other informed analyses of the conditions that might be present given it's distance to the star and other factors.
It's atmospheric composition can also be determined with spectroscopy.
If you really think astronomers are just guessing, you couldn't be more wrong. It's true that there is a lot that we don't know about these planets, but what we do is built on a solid mathematical foundation.
It's not for a lack of trying... Generally, "habitable" and "promoting complex life" are probably two different things (for one, comfortably habitable (by the criteria from my link) planets might be, from certain point on, way too active for stable complex ecosystems). And "promoting intelligence" - another thing. "Leading to technological civilization" - yet another. That might be enough of an explanation. We're here for a blink of an eye, so far.
One that hath name thou can not otter