Kepler mission – stellar smear and a grain of salt
After yesterday’s release of Kepler’s first light images and being marvelled by the telescope’s full field of view I was here wondering how would look one of the several raw images composing that breathtaking view into a sea of stars.
And, now that we’re into the real stuff and aware that we won’t hear of an Earth-like planet until the team has full confirmation, for when, hipotetically, could we expect one of those candidates to make its first appearance? How soon can it be?
Natalie Batalha answers:
What does a raw image look like? Our camera does not have a shutter, so it is always exposed to light — even when the electronics are reading out the CCD’s. In that short time, star light smears down the CCD columns. It’s very noticeable for the brightest stars. We corrected that out before displaying the first-light image. That’s one example. There are other calibration steps as well, but the smear is the most noticeable.
We hope to begin analyzing the first 6 weeks of data towards the end of the summer. Right away we will see the three known transiting planets in our field. We’ll see them because they are giant planets in short-period orbits (e.g. easy to spot). We will likely detect other transiting objects by the end of the year as well. However, there are other astrophysical signals which can confound us. But we are prepared for this! We have a team of astronomers that will work had to separate the true planets from the other signals. This data “vetting” will take more time as it involves taking follow-up observations from telescopes on Earth. And remember: our ground-based telescopes can only point to the Cygnus region of the sky from about April through October. They’ll have to stop taking observations during winter, though I’m sure they’ll have plenty of work analyzing data to keep them busy! With all this I haven’t really answered your question, have I? You asked specifically about an Earth-like planet. If you mean a habitable Earth-like planet orbiting a Sun-like star, then you’ll truly have to wait the full four years for such a result. However, it is possible that we might find a habitable, Earth-like planet orbiting a much cooler star. In this case, the orbital period is much shorter so we won’t have to wait so long to see multiple transits. Even so, the same vetting and confirmation procedures apply. I suspect it’ll be a couple years before we’ll be able to announce these “earths” orbiting cool “suns”. That’s only slightly better than a guess, so take it with a grain of salt.