From PBS: Time Runs Out for Telescope, Examining Kepler's Contribution to Space Research
JUDY WOODRUFF: The U.S. space agency confirmed yesterday that its renowned Kepler telescope is beyond repair, a big blow in its search for planets.
The Kepler was launched into an orbit around the sun in 2009, its purpose, observe stars thousands of light years from Earth that may harbor Earth-like planets. By looking at what happens to the light emanated by the stars, it's discovered more than 3,500 possible planets, more than 100 of which have been independently confirmed.
But it has not yet found one planet that has the right conditions for sustaining life as here on Earth. NASA says the spacecraft's wheels, which are critical for keeping it pointed correctly, do not work anymore. Astronomers are now assessing its legacy.
Michael Lemonick is the author of a book about Kepler called “Mirror Earth." He has long written about space and science for TIME magazine.
Michael Lemonick, welcome to the NewsHour.
Tell us a little bit more about what the original mission for the Kepler was.
MICHAEL LEMONICK, author: The original mission was to take a census, really, of a group of stars, an average group of stars, to find out what percentage of them have planets of any kind, and what sizes those planets come in and how far they are from their stars, how the temperature on the surface of those planets would be, if you were there.
JUDY WOODRUFF: And why is that important? And how much of that mission did it get done?
MICHAEL LEMONICK: It got -- well, first of all, it got a huge amount done.
It's important because when -- the reason we look for planets around other stars at all is because we're interested in whether there is life elsewhere in the universe. And the best bet for life, we would think, would be on a planet just like Earth, that is, about the same size as Earth, orbiting a star like sun, with the right temperature for water to exist in liquid form, which is a requirement for life, we think.
And since we know there's a planet like that already in the universe, and life is here, we want to look for a planet like that elsewhere as the best bet for finding life.
JUDY WOODRUFF: And so what happened to the telescope? We mentioned the wheels not working. What -- was this something they expected would go wrong?
MICHAEL LEMONICK: Well, so, these wheels help the telescope point very precisely at the stars it's looking at.
You have to hold the telescope very steady in order to detect the very faint fluctuations in light that happen when a planet goes in front of a star, so it dims just a tiny bit. And the wheels help keep it pointed incredibly precisely. And they have had four of these reaction wheels that the satellite went up with.
One of them failed last year. Another one failed last spring. And with only two wheels still working, you can't point with the accuracy that you need. And so the telescope is still in perfect working order. It just can't aim in the direction that it's supposed to.
JUDY WOODRUFF: Michael Lemonick, it must be incredibly frustrating for the NASA scientists who put so much effort into this. How are they taking it?
MICHAEL LEMONICK: Well, they're actually taking it pretty well. When Kepler was first approved in 2000, it was approved for a four-year mission. That's what the scientists asked for. And NASA said, yes, you can have four years.
And they have completed the four years. In 2012, the scientists said, wow, we could do better science if we had another several years, and they got another three-and-a-half. But the first primary phase of the mission has been completed. And only the first two years worth of data from those four years have been analyzed yet. And those numbers you quoted in the introduction, all those planets it's found already, that's just from the first two years of data.
So they have got two more years' worth to probe through, many more discoveries to make. All they're -- all that is lacking is the ability to then go even deeper and look even further. So they're disappointed, of course. They would have liked to do more with this amazing satellite, but they're incredibly satisfied with what they found already.
JUDY WOODRUFF: But in terms of adding to our understanding of space, you're saying this is significant?
MICHAEL LEMONICK: This is very significant.
What they have done in the survey is discovered what they are convinced are more than 3,000 planets. They haven't all been confirmed yet, but most of them will be. And what they see is that if you look out around average stars, you will see some planets, like Jupiter, big, gassy, giant planets that would be very inhospitable to life, more, smaller planets like Neptune, still not very hospitable.
But as you get smaller and smaller and closer to Earth in size, there are more and more planets. And if they extrapolate from what they have seen, one estimate, one lowball estimate is that in the Milky Way, there would be 17 billion planets with just the right conditions for life, and that's a low estimate. There are probably more than that.
So, we didn't know any of this before Kepler. Now we know that Earth-like planets are almost certainly very common in the Milky Way. Fifteen years ago, we didn't even know there were planets at all around other stars. Now we know that Earths are very common in the Milky Way.
JUDY WOODRUFF: And what do they believe it's going to take to find out where those other Earths are?
MICHAEL LEMONICK: Well, so Kepler's primary mission is often misunderstood.
It wasn't specifically to find those planets in particular. It was to get an idea of how common they are. That's the basic mission. So, if it found that Earth-like planets are very rare, that tells astronomers, OK, maybe it's not worth going out now and trying to find specific ones. What it's found instead is that Earth-like planets are probably very common.
There are probably plenty of them reasonably close to us, and now we can start targeting, with new telescopes, targeting stars closer to Earth than the Kepler stars, which are quite far away, looking for those planets, and, ultimately, with more powerful telescopes, looking at their atmospheres and their surfaces to try and determine whether there's really life there, because it's one thing to say, yes, this is a good place where life could exist.
We want to be able to say, yes, life does exist on these planets. And that is now not a crazy thing to try and do, thanks to Kepler. We now know it's not a quixotic endeavor.
JUDY WOODRUFF: Well, that is pretty exciting.
Michael Lemonick, thank you very much.
MICHAEL LEMONICK: I think so.
Thank you.
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