Tuesday, March 12, 2013

"a patch of sky"

From the interview Kritsa Tippett has with Natalie Batalha:
Ms. Batalha: So what we're doing is we're measuring the brightnesses of stars. We're not actually taking pictures of stars and planets. We're measuring their brightnesses. And in this one patch of sky that we're looking at, like you said, there are millions of stars, literally 4.5 million stars near the Milky Way, the plain of the Milky Way, a patch of sky that's about the size of my open hand, you know, stretched out in front of me. 
And we've chosen about 150,000 that we're monitoring. So we collect the light through a space telescope and that light is sent down to a detector, which is just an array of CCDs. It's exactly what you have in your digital camera when you take a picture. And those detectors are measuring the amount of light that falls on them from these 150,000 stars. So we take a measurement of all these stars simultaneously once every 30 minutes, and we've been doing that for three and half years [laugh]. 
And the point is, you take these measurements and you want to do it without blinking because eventually some of those stars are going to have planetary systems that are orbiting and aligned in such a way that the planet will pass directly between our telescope and the star. And when it does that, that planet is going to cast its shadow out into space and that shadow is going to sweep across our telescope and our detectors are going to perceive that as a dimming of light. So that's how we're inferring the existence of the planets. Those signals are tiny and they last, you know, a couple of hours and they repeat once every year. So you really do need patience. You need to stare at these things consistently without blinking waiting for these signals to occur.

So that is "a patch of sky that's about the size of my open hand"
Yes, your hand, stretch it out and see how big it is.

Listen to the whole interview here:  http://www.onbeing.org/program/on-exoplanets-and-love/5029