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| An artist's impression of TRAPPIST-1 and its seven planets |
Excerpt
SUMMARY: Astronomers have identified seven Earth-sized planets orbiting a star that's just a mere 230 trillion miles from our own planet, raising the tantalizing prospect of life in a solar system beyond our own. Science correspondent Miles O'Brien joins Hari Sreenivasan to discuss how they made the discovery and what it means.
HARI SREENIVASAN (NewsHour): Now to this week's edition of Leading Edge.
There is new excitement tonight about the search for possible life in a solar system beyond our own. Astronomers have identified seven Earth-sized planets orbiting a star just a mere 230 trillion miles or so from our own planet. That sounds like a mind-boggling distance. It is. But researchers say the idea of life on one of these exoplanets, as they're called, is tantalizing.
Astronomers, using ground and space telescopes operated by NASA and the European Southern Observatory, made the announcement.
Our own Miles O'Brien is here to guide us through the news.
First of all, if something is so far away — this is maybe a basic science question — how do we know what we know and what we saw?
MILES O'BRIEN (NewsHour): It's a good question.
You know, think about it for a minute. If it's trillions of miles away, how is it even possible? So, imagine — the technique is called transit photometry. Now, imagine you're about a mile away from a headlight and a mosquito goes across the headlight.
Believe it not, that headlight is slightly dimmed by the fact that mosquito goes across. Well, this is tantamount to what they do. The planet goes in front of the star, it dims ever so slightly, and with a lot of complicated and sensitive instrumentation, you can determine that, in fact, that's a planet.
They discovered three of them this way. They said, hmm, this is an interesting, ultra-cool brown dwarf to look at. Let's put some more hardware on it. They set more instrumentation on it. And, sure enough, there ended up to be seven Earth-like planets, just about the size and mass of Earth, orbiting this Jupiter-sized, ultra-cool brown dwarf.
HARI SREENIVASAN: Now, you say ultra-cool, that doesn't mean it's a cold sun. It's just not as big or as hot as ours, right?
MILES O'BRIEN: It's about like Jupiter is to us, OK, cooler and smaller.
HARI SREENIVASAN: And when we talk about this habitable zone, this Goldilocks, not too cold, not too hot, how do they know that there are planets in this group that exist within that range?
MILES O'BRIEN: They can measure the radiation off of TRAPPIST-1, this particular ultra-cool brown dwarf, and figure out the zone at which water would remain liquid. And that's the key.
Everywhere we look on this planet and we find liquid water, we find life. It doesn't matter where we go. So, in the hunt for potential alien life, the thought of finding places where there is liquid water is what really intrigues scientists.
So, these planets are a lot closer to TRAPPIST-1 than we are to our sun, but, remember, it's smaller and dimmer. And they have these very tight little orbits. And it's quite likely there might be water on some of them.
NASA Announcement Video (38:32)
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