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My Very Educated Mother Just Showed Us New Planets — 1,200 of Them

February 3, 2011 at 5:35 PM EDT
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Perhaps you learned a mnemonic device such as the one above to help remember the planets -- Mercury, Venus, Earth, etc. -- and their order away from the sun. Turns out, we're going to need a longer mnemonic after the discovery of some 1,200 planets outside our solar system. Miles O'Brien discusses the findings with Jim Lehrer.

JIM LEHRER: Now, news about new planets.

NASA scientists announced the number of known planets beyond our solar system may have just tripled. The discovery came through the Kepler telescope, which identified more than 1,200 likely new planets. They included a family of six planets orbiting a sun-like star, the most populated planet system yet found outside our own.

Fortunately, NewsHour science correspondent Miles O’Brien is here, and he will now tell us all about it.

Miles, welcome.

MILES O’BRIEN: Jim, good to be with you.

JIM LEHRER: The — a scientist said today — and I quote him — “An extraordinary — this is an extraordinary planet windfall, a moment that will be written in textbooks.”

Miles, what should be written in textbooks about this discovery?

MILES O’BRIEN: Well, it turns science fiction into science fact, Jim.

You know, it was only about 20 years ago the total number of known exoplanets was zero. And now we’re approaching 1,800 planets outside our solar systems of various sizes and shapes and consistencies, if you will, some of them big gassy giants, some of them smaller and rocky, that are out there orbiting other stars, or their suns.

And that is such a significant moment, because, when you consider Kepler was looking at a little piece of our sky, one-four-hundredth of the nighttime sky, and in the course of a four-month period finds 1,200 planets, 54 of them in a zone where water could occur — they call that the habitable zone — and five of the planets inside that habitable zone about the size of Earth.

So, if you start to extrapolate that out to the entire nighttime sky, it seems highly unlikely that we are alone.

JIM LEHRER: OK. You mean that literally?

MILES O’BRIEN: Yes, I think so. I think we’re talking about hundreds of thousands of planets out there.

And, you know, there are many astronomers who would say, if you just start doing the math on all this, there are probably many millions of planets out there. And many of them would be habitable. Many of them could be Earth-like. The question is how will we find out?

JIM LEHRER: And when will we find out?

MILES O’BRIEN: Well, it’s going to take another few years down the road, but it’s getting close. Kepler’s goal is to sort of do a head count, if you will, find out how many are out there in this little piece of the sky, make people feel that this is a mission worth doing, and then follow-on missions will actually be able to detect these planets more directly.

You know, the way Kepler works, it’s kind of like trying to look for a mosquito that is passing in front of a lit headlight at night. That’s what a planet hunt is like. And so Kepler is able to detect the dimming of that light caused by the mosquito going in front of the headlight, if you will.

Now, the next step is to come up with telescopes that can actually see, despite the brightness of the star, directly see those planets. Once you can do that, you can start determining, well, maybe there’s water on there, are there organic compounds, you know, the telltale signs of life. That will happen in follow-all missions that we hope will launch before too long.

JIM LEHRER: Is there a simple lay definition of what a planet actually is? What do you have to be to be a planet?

MILES O’BRIEN: Well, yes, I mean, we could — we could get into the whole Pluto debate here, if you wanted to.

JIM LEHRER: Sure. Sure.


MILES O’BRIEN: What does it take to be a planet? Yes, it’s not a simple thing, and it’s subject to a fair amount of debate.

But, basically, we’re talking about a core, a central core. We like to think of something that has a nice regular circularized orbit, if possible, something that’s around a star and is orbiting in the way we think of in our solar system.

But, you know, as we found out with Pluto, it got taken off the planetary list and is now considered something more akin to an overgrown asteroid.

So, there is a gray area, to say the least. And, as we look more closely into this finding, with the 1,200 planets, some of them will turn out to be false alarms, and some of them may turn out to not be planets that we’re so interested in. But there’s got to be a few in there that are in a so-called Goldilocks zone, the “not too hot, not too cold” zone, where water can be present, which might have a rocky surface, which might lead us to believe there’s life.

JIM LEHRER: And, so, in terms of size, compare? What are like these 50, the 51 — what is it, 52, that they say…

MILES O’BRIEN: Well, yes, there are — there are 54 of them…

JIM LEHRER: Fifty-four.

MILES O’BRIEN: … 54 of them that are just about the size of Earth.

JIM LEHRER: About the size — OK.

MILES O’BRIEN: And, you know, give or take Earth, OK? And — and — excuse me — let me get that right. Fifty-four of them are in the habitable zone. There were 68 that were total that were about Earth-size…


MILES O’BRIEN: … 54 in the habitable zone.

Of those, five are the size of Earth. Now, that still doesn’t tell us. They could still be gas-sized Earths, in which case there wouldn’t necessarily be life as we know it. We need to do further investigation to understand the density of those planets. Are they solid planets, or are they just gas balls? If they’re gas balls, it’s less likely there will be life as we know it.

JIM LEHRER: So, what is the next immediate step? Are there, in fact, immediate steps that Kepler — using Kepler or anything else, NASA is going to see, to find out, to answer some of these still-unanswered questions?

MILES O’BRIEN: Well, Kepler will keep looking and keep doing this — this census. But this announcement really gives a lot of momentum and a lot of push for the follow-on mission, the Terrestrial Planet Finder, which NASA would like to fly, another mission called Darwin of similar nature.

And those missions will — will come up with ways of looking at these planets in a direct way, actually observing them directly. It’s very difficult when that you have bright star nearby. And the planets that we’re finding are pretty close to the star, relatively speaking, particularly from the distance we’re looking.

So, it’s difficult to root that out. There are ways to do it. It’s not an inexpensive thing, but scientifically, can you think of a more fundamental and more exciting question to have an answer to: Are we alone?


And that’s really what it’s about, right, Miles?


JIM LEHRER: I mean, if we — we are going to find out one way or another if we were alone, and that’s all we’re going to find out, though, probably?

MILES O’BRIEN: Well, yes, because it’s the — the tricky part is, let’s say — for example, you talked about that cluster of planets that Kepler discovered.


MILES O’BRIEN: Well, those planets are 2,000 light years away. So, if we were to try — let’s say, for example, we were to discover that there was some sort of intelligent life there.

It’s kind of hard to have a meaningful dialogue if a two-way discussion takes a 4,000-year round-trip. The punchline and the humor don’t go so well over 4,000 years, I would say, yes.


Also, defense systems do not have to immediately get geared up for any kind of an attack.



MILES O’BRIEN: No, there’s no — there’s no Orson Welles component to this one that I know of.

JIM LEHRER: OK. Not yet, at least. OK.


JIM LEHRER: Miles, thank you very much.

MILES O’BRIEN: Pleasure, Jim.