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An Earth-sized exoplanet has been found in the habitable zone of another star. The discovery, using data gathered by NASA's productive Kepler space telescope, is the first of its kind. The planet, Kepler-186f, orbits a star of the common red dwarf type. Stars of this class have a mass of about 1/2 that of our sun, and are the most common type of star in our galaxy. The planet itself has an orbital period of 130 days, and "receives one-third the energy from its star that Earth gets from the sun, placing it nearer the outer edge of the habitable zone. On the surface of Kepler-186f, the brightness of its star at high noon is only as bright as our sun appears to us about an hour before sunset."
The paper that discusses the discovery is freely accessible, along with dedicated webpages hosting the press kit, and a webpage on the Planetary Habitability Laboratory site.
Maybe it's a little far away for a visit, but this should be an interesting target for exoplanet imaging in the future!
(Score: 2) by Foobar Bazbot on Friday April 18 2014, @07:30PM
If it were shown that Alpha Centauri (or any other star <10ly distant) had a habitable-zone planet, I don't think there'd be a problem funding a FOCAL mission (pdf [snolab.ca], or use your favorite search engine) to examine it.
(Score: 2) by mcgrew on Saturday April 19 2014, @01:29PM
Interesting, thank you for the link. But FOCAL is studying 500 to 1000 AU, 1000 AU is only 0.015 light years. Alpha is 250 times as far away.
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(Score: 3, Informative) by Foobar Bazbot on Sunday April 20 2014, @06:19PM
No, FOCAL isn't studying 500-1000 AUs, it's putting a telescope at 500-1000 AU -- or rather half a telescope, as the other half is the sun, acting as a gravitational objective lens. This telescope can then examine distant targets with incredible resolution -- I've seen calculations putting the diffraction limit on the order of 10m at nearby stars, so even if you can't approach the diffraction limit and get only 1km resolution in practice, it's still amazing. And it works for all bands (radio, IR, visible, even gamma rays!), just a matter of putting appropriate sensors in the image array.
The downside is that, because your telescope is 500-1000 AU long, you can't steer it very far at all; you pick one target, lob a FOCAL mission on an escape trajectory* in the opposite direction; for each additional target, you launch a separate FOCAL mission. Each probe has a limited delta-v budget for aiming, enough for a carefully-planned sweep over Alpha Centauri A, Alpha Centauri B, and any planets with pre-known orbits, but likely not enough to do an extensive survey for previously unknown planets. Of course a given angular deflection needs more delta-v as you go farther, so you want the trajectory pre-planned as much as possible.
*There is, of course, the idea of orbiting an image array at 1000 AU, aligned to sweep across several targets of interest, but this is either much harder or much slower than an escape trajectory, and still only gets you one great circle track, presuming it remains operational that long. The idea becomes more interesting as one goes to 15000 AU or so, where it becomes possible to choose between the sun and several planets as gravitational lenses; by taking advantage of those planets' orbital motions, a single orbit (or the tiny fraction of one within reasonable time) gets a much wider band of targets. In addition to the obvious difficulty of orbiting a vehicle at 15000 AU, and of building it to last long enough to be useful in such a slow orbit, the greater distance results in greater magnification, and thus requires a proportionally larger image array. In general, escape-trajectory, solar-objective missions (with possible extended missions using planetary objectives, if they remain operational to that range) for now, and building on that to orbital, solar- and planetary-objective missions later, seems like the way to go.