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JUDY WOODRUFF: And now for something
out of this world.
NASA scientists think they have discovered the most Earth-like planet yet circling a star that’s about 500 light
years away from us. For now, you can just call it Kepler-186f.
Hari Sreenivasan is in our New York studio, and he has a fuller look at why it’s exciting astronomers.
HARI SREENIVASAN: It was discovered by the Kepler space telescope. And as shown in this animation, it’s said
to be in a so-called Goldilocks zone, where it’s not too far from its sun, Kepler-186, and its temperatures could be
just the right environment to allow liquid water to flow on its surface.
Tom Barclay is part of the NASA team and with the Bay Area Environmental Research Institute. He joins us from Mountain
So, if — Judy said this is 500 light years away. Why is this discovery so consequential?
TOM BARCLAY, NASA Ames Research Center: So, while we won’t be going there any time soon, this really demonstrates
that there are planets the same size as our own within the habitable zone of other stars.
The habitable zone is a region where we think, with the right atmospheric conditions, liquid water could exist on the surface.
Now, we don’t know whether this planet does have an atmosphere, but if it did, we could — and it had similar characteristics
to our own, had greenhouse gases that heated the planet, it could host liquid water.
HARI SREENIVASAN: So, there’s been a lot of attention today to the size of the planet being so Earth-like.
Why does that matter?
TOM BARCLAY: So, the one planet where we know there’s life is our own. And that’s an Earth-size planet.
In our own solar system, there are two Earth-size planet. There’s Earth and Venus. Both those are rocky. So we deduce
by proxy that this planet may well be rocky.
There were a number of other planets discovered, the smallest of which in the habitable zone is about 40 percent bigger
than Earth. These are called super Earth-size bodies. And they may be rocky. They may have a significant amount of liquid
water around their surface.
But they don’t remind us of home. They’re much more massive. They may be six to eight times as massive as our
own planet. The gravity is going to be much higher. They may be much hotter inside, so they don’t have layers like our
own planet, with a core, a mantle and a crust.
This planet, while we don’t know for sure what it looks like, probably could well be rocky, could well have similar
characteristics to our planet.
HARI SREENIVASAN: So, let’s do a thought experiment for our audience, if you will.
Let’s say we devise sort of vehicle that bends space and time travel 500 light years, and you and I are standing
on the surface of this particular planet. What does life look like, what does it feel like while we’re standing there?
TOM BARCLAY: So, this planet orbits a star that is cooler than our own.
It’s slightly oranger, so if you looked in the sky, it wouldn’t appear like the white sun we see. It would
slightly more orange. This star also reveals less starlight than we receive from the sun. So, it will be a bit dimmer on the
surface. Perhaps at midday on the surface of this planet, you would receive a similar sort of illumination to that what we
receive maybe an hour before sunset.
There wouldn’t be the rich blues you see from our orange. It would be a much duller color. And that’s because
there’s not as much blue light coming from its star because it more orangey, more red. There’s less blue light,
less blue light to scatter, so the ocean’s duller.
The clouds and the ice on this planet would be a similar color to their star, rather than the white clouds and ice we see.
So they may all be an orangey color as well.
HARI SREENIVASAN: Let’s say, just on the basic physics that we understand about Earth, if this is slightly
larger, does that change the gravity and, for example, how we feel we weigh?
TOM BARCLAY: Yes, so this one is very comparable to Earth.
If it was exactly 10 percent larger than Earth, you would feel a little — and it was made of the same thing as Earth
— you would feel slightly more gravity, maybe 40 percent more. It wouldn’t be vastly different.
You know, people go at 40 percent more g force fairly regularly without feeling significantly different. So, you wouldn’t
— it wouldn’t be that unusual for us.
HARI SREENIVASAN: And we’re spinning around that star how fast? Not 365 days for a whole year?
TOM BARCLAY: No, their year would be much shorter.
Because the star is cooler, the region where liquid water could exist, the habitable zone, is located much closer in.
So, while we go around our star once every 365 days, they go around their star once every 130 days. So, the star —
so the year — you would have many more birthdays.
HARI SREENIVASAN: That’s not so bad news.
OK, so let’s talk about next steps. This was from data that you had from the Kepler telescope. What’s the next
telescope and what is it going to look for?
TOM BARCLAY: So, as mentioned, you mentioned at the start, this start is about 500 light years away. This is not
an especially bright star. We couldn’t see it with our own eyes.
The next step is to try and find planets orbiting much brighter stars, much closer-by stars. So, NASA is launching a mission
called the Transiting Exoplanet Survey Satellite, or TESS, in a couple of years, specifically to find planets similar to this
one, but orbiting our nearest neighbors in our cosmic backyard.
Once we have found those, spacecraft like the James Webb Space Telescope will try and study their atmospheres to tell whether
there is a similar atmosphere to our own. Is there oxygen? Is there carbon dioxide? Is there water vapor and nitrogen, the
right things to — that are conducive to life?
HARI SREENIVASAN: All right, Tom Barclay, thanks so much for joining us.
TOM BARCLAY: Thank you.
The post Kepler telescope spots
a planet that seems a lot like home appeared first on PBS NewsHour.