1,091 new transiting planet candidates have emerged from analysis of Kepler spacecraft data spanning May 2009 to September 2010, bringing the total count to 2,321 Kepler planet candidates orbiting 1,790 host stars. A clear trend toward smaller planets at longer orbital periods is evident with each new catalog release. This suggests that Earth-size planets in the habitable zone are forthcoming if, indeed, such planets are abundant.
The largest increases in planet candidates in the current release are for the smallest ones. The cumulative catalog now contains over 200 Earth-size planet candidates and more than 900 that are smaller than twice Earth-size (super-Earths), a 197% increase (compared to a 52% increase in number of candidates larger than 2 Earth radii).
There is 123% increase in planet candidates with orbital periods (time taken to orbit the star) greater than of 50-days versus 85% for candidate periods less than 50-days.
Of the 46 planet candidates found in the habitable zone (where liquid water could exist), 10 are near-Earth-size. The gains in smaller size and longer period candidates are larger than expected and indicate significant improvements the Kepler data analysis software.
The fraction of host stars with multiple candidates has grown from 17% to 20%.
The previously found dearth of short-orbital-period giant planets in multiple systems is still evident in the new planet candidate catalog. Needless to say, the unfolding story of Kepler planet candidates has major implications for theories of planetary system formation.
The data for identifying Kepler planet candidates is in the form of exquisitely precise measurement of star brightness which decreases by a minuscule amount when a planet moves in front of (transits) the star. So precise is the data that even small planets that block even less than 1/100 of 1% of the star's brightness can be detected. In the process of identifying the new planet candidates, nearly five thousand periodic transit-like signals are vetted against known phenomena that could masquerade as transits (false positives). The most common false positives are associated with eclipsing binary stars (two stars orbiting each other and regularly blocking each others light).
The 10 near-Earth-size candidates sound promising, although we'd need to confirm both them and try to get their masses before any real hopeful speculation.
After that, though, it likely gets much harder. You'd have to separate the light reflecting off the planet from the light of the host star, and do a spectroscopy on it to hopefully find out the composition of the planet's atmosphere.
“It is possible to commit no mistakes and still lose. That is not a weakness. That is life.” -Jean-Luc Picard
"Men are afraid that women will laugh at them. Women are afraid that men will kill them." -Margaret Atwood
Unless our own solar system is hugely atypical (not just in the existence of Earth, but in the existence of Mars, Venus, and Mercury), then there should be a lot of Earth-and-smaller planets out there, possibly outnumbering all the 'super-Earths,' though not necessarily the gas giants.
I have often wondered exactly what Kepler would be able to see if you pointed it at an exact copy of our own solar system, at varying distances (ten light years, fifty, a hundred, and so on).
Simon_Jester wrote:Unless our own solar system is hugely atypical (not just in the existence of Earth, but in the existence of Mars, Venus, and Mercury), then there should be a lot of Earth-and-smaller planets out there, possibly outnumbering all the 'super-Earths,' though not necessarily the gas giants.
I have often wondered exactly what Kepler would be able to see if you pointed it at an exact copy of our own solar system, at varying distances (ten light years, fifty, a hundred, and so on).
This is why my Planetary Science lecture keep changing. When I startted it was "small planets form close in, large planets form further out in xyz manner. We assume this base on our (ordinary, typical etc) solar system."
Now, it's "We've no idea quite what happens and why it apparently didn't happen in our solar system. Discuss. Seriously, if you have any ideas we'd love to hear them; the models keep changing so you'll probably be right in a few weeks."
Baltar: "I don't want to miss a moment of the last Battlestar's destruction!"
Centurion: "Sir, I really think you should look at the other Battlestar."
Baltar: "What are you babbling about other...it's impossible!"
Centurion: "No. It is a Battlestar."
Corrax Entry 7:17: So you walk eternally through the shadow realms, standing against evil where all others falter. May your thirst for retribution never quench, may the blood on your sword never dry, and may we never need you again.
Simon_Jester wrote:Unless our own solar system is hugely atypical (not just in the existence of Earth, but in the existence of Mars, Venus, and Mercury), then there should be a lot of Earth-and-smaller planets out there, possibly outnumbering all the 'super-Earths,' though not necessarily the gas giants.
I have often wondered exactly what Kepler would be able to see if you pointed it at an exact copy of our own solar system, at varying distances (ten light years, fifty, a hundred, and so on).
Hard to say. You'd need to get lucky enough to see the planets transiting across the star, which means that you have to catch the solar system "on edge".
Kepler would likely identify our planets as "planet candidates" immediately, but it would take time to confirm it. Kepler usually uses three observed transits to confirm a candidate, which means it would take 3 years to identify Earth unless other telescopes are doing the same thing IIRC. That's also why Kepler finds so many planets close to stars - it's easier to confirm the transits.
“It is possible to commit no mistakes and still lose. That is not a weakness. That is life.” -Jean-Luc Picard
"Men are afraid that women will laugh at them. Women are afraid that men will kill them." -Margaret Atwood
Star systems with planets that transit across the star from our point of view should be a representative sample (more or less) of all solar systems... but yes, the confirmation of planet candidates is an obvious issue.
I would like to think, though, that someone did a simulation of what Kepler would see if pointed at Sol system (edge on) at varying distances. This would give us important information- when you take observations, knowing what your instrument can't see may be more important than knowing what it does see.
