A quick peek before the announcement today:1,000 possible new planets found90 per cent of discoveries by Kepler telescope expected to be verified as planetshttp://www.cbc.ca/technology/story/2011/02/02/science-space-kepler-planets.html
....(2) Kepler currently has had a sufficient observing interval to observe exoplanets with revolving periods up to four months. The habitable zone extends to something like revolving periods of eighteen months. So currently Kepler has observed for say one-fourth of the time required to observe all potentially habitable exoplanets....
Quote from: Nittany Lion on 02/02/2011 09:48 pm....(2) Kepler currently has had a sufficient observing interval to observe exoplanets with revolving periods up to four months. The habitable zone extends to something like revolving periods of eighteen months. So currently Kepler has observed for say one-fourth of the time required to observe all potentially habitable exoplanets....Three transits are required for sure detection of an exoplanet, so for detecting Earth from far away using Kepler's techniques would require between 24 and 36 months (plus the good fortune of your detector being in plane with the star system's Ecliptic).Stars smaller (or much smaller) than the Sun have a habitable zone closer (or much closer) in. Those are the sort of stars around which Kepler has found planets in the habitable zone since Kepler has only been operating for about 22 months. I.e. Red dwarfs.
"plus the good fortune of your detector being in plane with the star system's Ecliptic"Thus my point (3) which is the dominating effect in the calculation.
The probability of a random planetary orbit being along the line-of-sight to a star is the diameter of the star divided by the diameter of the orbit.[16] For an Earth-like planet at 1 AU transiting a Sol-like star the probability is 0.465%, or about 1 in 215. At 0.72 AU (the orbital distance of Venus) the probability is slightly larger, at 0.65%; such planets could be Earth-like if the host star is a late G-type star such as Tau Ceti. In addition, because planets in a given system tend to orbit in similar planes, the possibility of multiple detections around a single star is actually rather high. For instance, if an alien Kepler-like mission observed Earth transiting the Sun, there is a 12% chance of also seeing Venus transit.
Quote from: Nittany Lion on 02/02/2011 11:10 pm"plus the good fortune of your detector being in plane with the star system's Ecliptic"Thus my point (3) which is the dominating effect in the calculation.QuoteThe probability of a random planetary orbit being along the line-of-sight to a star is the diameter of the star divided by the diameter of the orbit.[16] For an Earth-like planet at 1 AU transiting a Sol-like star the probability is 0.465%, or about 1 in 215. At 0.72 AU (the orbital distance of Venus) the probability is slightly larger, at 0.65%; such planets could be Earth-like if the host star is a late G-type star such as Tau Ceti. In addition, because planets in a given system tend to orbit in similar planes, the possibility of multiple detections around a single star is actually rather high. For instance, if an alien Kepler-like mission observed Earth transiting the Sun, there is a 12% chance of also seeing Venus transit.
Quote from: kkattula on 02/03/2011 12:58 amQuote from: Nittany Lion on 02/02/2011 11:10 pm"plus the good fortune of your detector being in plane with the star system's Ecliptic"Thus my point (3) which is the dominating effect in the calculation.QuoteThe probability of a random planetary orbit being along the line-of-sight to a star is the diameter of the star divided by the diameter of the orbit.[16] For an Earth-like planet at 1 AU transiting a Sol-like star the probability is 0.465%, or about 1 in 215. At 0.72 AU (the orbital distance of Venus) the probability is slightly larger, at 0.65%; such planets could be Earth-like if the host star is a late G-type star such as Tau Ceti. In addition, because planets in a given system tend to orbit in similar planes, the possibility of multiple detections around a single star is actually rather high. For instance, if an alien Kepler-like mission observed Earth transiting the Sun, there is a 12% chance of also seeing Venus transit.Could you provide the source of that quote and the cited [16] reference?Although the quote indicates it is answering my planar question, the process seems to be describing the probability of observing a transit of an exoplanet whose orbit is already in the required orientation, i.e., the ratio of the star’s diameter to the orbit’s diameter. It strikes me that this is a two dimensional answer to a three dimensional problem.And the probability seems high.I’m not saying it’s wrong. I’d just like to pursue it further.
Added references to my previous post.The thing is, a star is not a point source. It's big. Really big.This diagram shows something like a super-Jupiter at .15 AU from a Sol like star. Any observer anywhere in the arc a, as it rotates 360 deg around the star, will observe a transit.Even if the planet is tiny, the arc doesn't change much. The intersection point is effectively at the planet's orbital radius
Keep in mind also, that Kepler is looking in a direction in which it expected to find many stars with possible planets - it's looking down the spiral arm of the Milky Way. So just saying that it's taking 1/400 of the sky, and so multiplying discoveries by 400, is definitely a high upper bound. If it was looking perpendicular to the galactic plane, it wouldn't be seeing nearly as many stars.