PBS高端访谈:科学家发现宜居新行星 离地球4光年

 　　HARI SREENIVASAN: Time now for our weekly segment on science called the Leading Edge, and the discovery of another possible Earth-like planet that's grabbing worldwide attention today.

　　It is true, scientists have previously 1 said they believe there are other planets outside our solar system that resemble Earth in size and may have liquid water. But this latest finding is the closest planet yet found. Yes, it's four light years from Earth, just a mere 2 25 trillion miles away. But travel there may be possible by the end of the century, maybe not for me and you.
　　The planet is called Proxima b, circling a small star called Proxima Centauri. As shown in this animation 3, it's thought to be about 1.3 times the mass of Earth, probably rocky like the Earth, and possibly warm enough for liquid water.
　　Let's learn more now from our science correspondent and resident space expert, Miles O'Brien.
　　Miles, first of all, why are they so excited about this? We have heard about the planets and this kind of Goldilocks, not too hot, not too cold, places before?
　　MILES O'BRIEN: Location, location, location, Hari.
　　We're talking now of about more than 3,000 planets total, exoplanets in the catalogue, and growing by the minute, but this is the closest one that's been discovered. And that is what has scientists quite interested.
　　Four light years is, in astronomical 4 terms, a trip to the convenience store. And so the idea that there might be something somewhat within the realm of attainable 5 if we come up with some really cool rocket propulsion ideas gets people thinking.
　　HARI SREENIVASAN: How do we know it is what it is? We can't see it from our eyes. There's telescopes that see things, but they didn't really get a picture of this planet.
　　MILES O'BRIEN: It's indirect.
　　Imagine driving down a darkened highway and a car coming at with its high beams on. You don't know anything about that car, do you? But there are some ways to kind of figure this out using some interesting technology.
　　In this case, what they used was the slight wobble that occurs as these two bodies interact with each other. As the planet orbits around, the star itself moves ever so slightly. That's enough to infer that its presence is there.
　　There are a few other ways to do it. You can actually detect the slight diminishment of light as a planet passes in front of a star and infer that its presence is there that way. That's how the Kepler space telescope has done its work so well over the years for NASA.
　　科学家发现宜居新行星 离地球4光年
　　HARI SREENIVASAN: So, tell us what scientists think they know about this planet in relation to the Earth.
　　MILES O'BRIEN: Well, I don't think we want to live there, Hari.
　　It's 11 days around its star, so an 11-day year. It is tidily locked, which means there is a light side always and a dark side always. So I suppose the real estate on the light side might be better. I don't know. If you're a night owl 6, maybe you want to go to the other side.
　　It's very close to its star, but the star itself is a brown dwarf 7. It's a pretty wimpy 8 star. And so it can be closer and be in what scientists call the Goldilocks zone, the just-right zone where the temperatures are just right for water to exist in liquid form.
　　And here's the thing to remember. Wherever we look on this planet, no matter where we go, deep down in the ocean, in acid springs in Yellowstone, if there is liquid water, we find life.
　　HARI SREENIVASAN: And so there could possibly be — even under this star's light, there could be something maybe subterranean 9, life underground, or whatever constitutes ground on that planet?
　　MILES O'BRIEN: It will take a while, maybe a decade, to kind of figure this all out, because, again, we haven't seen it directly.
　　And — but this is something that has scientists very intrigued 10. And as technology improves — and NASA will be launching another spacecraft coming up in a year or so called TESS that will be a little more powerful and will be looking a little bit closer to us than its predecessor 11, Kepler.
　　Possibly, it will solve some of those questions for us and determine if, in fact, there might be life that close to us.
　　HARI SREENIVASAN: And so there are some projects kind of at least planned on getting very, very small sort of sensors 12 or objects out farther and farther into space. How could we ever, in our lifetimes, maybe not in our lifetime, our children's lifetimes, reach this to get a look at it?
　　MILES O'BRIEN: Well, we have to think about some new ways of doing propulsion in space.
　　Some sort of nuclear option is what we're talking about here. Once you get into space, if you can have steady propulsion that never stops, fueled by some sort of nuclear reaction, you continue to accelerate, because there's no friction 13 in space, of course.
　　And so ultimately you can develop some real speed. And, potentially, some ideas on the drawing board could make that trip of four light years something on the order of a century or maybe a little less.
　　Right now, if you wanted to, say, launch the space shuttle, not that it could go there, but if you wanted to, just for point of reference, it would be more than 100,000 years to get there. Voyager, for example, just leaving our solar system, if you aimed it at this newly discovered planet, voyager would take about 70,000 years to get there.
　　So, that gives you an idea, where it's not just billions and billions. We're talking trillions and trillions here.
　　HARI SREENIVASAN: And to get a photo back from there would take several years too.
　　MILES O'BRIEN: Well, you know, that's just it.
　　The speed of light, four-and-a-half light years away, so it's four-and-a-half years to get any transmission back and forth 14. So it would be really hard to engage in any sort of jokes with the people who might live on this planet.
　　You know, comedy is timing 15, of course.
　　HARI SREENIVASAN: Right.
　　Miles O'Brien joining us from Boston, thanks so much.
　　MILES O'BRIEN: You're welcome.