Remember that Kepler looks at stars using the "transit" method. Basically it stares at the little point of light for a looooong time, never blinking and waits to see if the light drops just a teeny bit due to something passing in front of it. How long? Well since it has to calculate the orbital period, it must watch at bare minimum for at least 1 year to see 2 passes (assuming its looking for a planet in an earthlike orbit around a sun-like star). Then, in order to make sure that it isn't some OTHER planet passing in front of the star, or an object in our solar system, or "sun spots" on the star, or maybe space butterflies getting in the way, the scientists must wait for a THIRD confirming pass (at the predicted time of course with the same drop in intensity) to be sure the observation is "real".
I think these guys have found the first "earth-sized" object that has made three confirmed passes. Note that the period is a bit less than a year so they've had enough time to get three observations in the three years. Soon, they'll be announcing confirming "third passes" on more and more planets that have periods in roughly the one-year window that indicates it's in the habitable zone around a sun-like star.
There are two things to note here: First, Kepler can only see planets that pass between it and the target star, that is the planet's orbit must be almost exactly edge on for us to see it. How close to edge on must it be? Well for example; the earth's orbit is a circle (very) roughly 100 million miles from the sun and the sun is roughly 1 million miles across. So, if the orbit was tilted more than 1/100 or 1%, from some distant observer, they wouldn't see it cross in front. (The size of the earth is inconsequential in this calculation because it is so small in relation to the sun). Similarly, for the kind of planets Kepler is looking at circling around sun-like stars, we are only seeing BY PURE CHANCE 1% of them. So if we see 100 planets circling these stars in their habitable zone; that means there are really 10,000 of them! So for a sample size of 150,000 stars, that means that one out of every 15 sunlike stars has planet in it's habitable zone! Amazing, especially when you consider our galaxy to have perhaps 10 BILLION sunlike stars!
Secondly, Kepler was launched before astronomers "discovered" that the best place to find "habitable" planets wasn't around sunlike stars but around smaller cooler stars. For various reasons, the habitable zone (where water can be a liquid) is proportionately larger in these "mini" solar systems (everything is smaller, like the orbits). They realized that even if a planet was tidally "locked" so that one face was always facing the sun, the atmosphere would redistribute the heat enough so the planet would be "habitable" (must sure be windy though). Another advantage is that these smaller stars live much longer than our sun giving life longer to come to well... life! Finally these smaller stars are much more numerous than sunlike stars. Anyway, I think Kepler was focusing mainly on sunlike stars and not these smaller, more numerous and perhaps easier to detect (because the orbits are smaller you don't have to wait as long for three passes) targets. Maybe Kepler II will go after them!
Just so that you know, Kepler is likely (has already?) been giving tons of other interesting data. I understand that its sensors are sensitive (and stable enough!) so as to detect possible sunspots in these stars. Also by paying close attention to the timing of the transits, they can determine whether other planets are gravitationally "tugging" at the transiting planet and perturbing its orbit (that's how Neptune was discovered). Finally, the resolution of the 'light curve" of the transit may be sharp enough to reveal any large moons in orbit around the transiting planet. So even if the planet in the habitable zone is too large to support life as we know it, it may have a right sized moon! (think "Pandora").
maksim chmerkovskiy aurora borealis s.978 larry ellison go ask alice go ask alice nflx
