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PRI's Environmental News Magazine


Air Date: Week of February 24, 2012

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An artist’s conception of GJ12-14b, a super-Earth orbiting a red dwarf star 40 light-years from Earth. (Photo: David A. Aguilar (CfA))

Planet GJ-1214b has a lot of water. But instead of oceans and lakes, its water is more likely in the form of steam and “hot ice.” Host Bruce Gellerman talks to Zachory Berta, a graduate student in astronomy at Harvard University. Along with a team of astronomers at the Harvard-Smithsonian Center for Astrophysics, Berta discovered and described this totally new type of planet.


GELLERMAN: And now for a trip to a very weird planet. If you blast off from Earth, head for the constellation the Serpent Bearer, and travel 40 years at the speed of light - you’ll hit the planet GJ12-14b. It's known as a super-Earth because of its size – nearly 3 times Earth’s diameter.

It weighs 7 times as much, and orbits a red dwarf star – but those are NOT the attributes that make GJ12-14b unique - it turns out it’s a totally new type of planet. Zachory Berta made the discovery, along with a team of astronomers at the Harvard-Smithsonian Center for Astrophysics.

BERTA: We think that GJ12-14b is a planet that has a lot of water in it– I mean, a lot of water in it. So, if the planet really is made - of a large part - a fraction of water, then you would expect that its atmosphere would also have a large amount in it. And so, we went and measured that atmosphere with the Hubble space telescope, and we found it looks like that atmosphere is made of a large fraction of water.

GELLERMAN: So, you have a watery planet.

BERTA: Yeah.

GELERMAN: But there are watery planets. I mean, we’ve got three quarters of our planet is watery - that’s not unique is it?

BERTA: Three quarters of the surface of our planet is water. But only a tiny fraction of a percent of the mass of our planet is water.

Zachory Berta and host Bruce Gellerman (Photo: Jessica Ilyse Kurn)


BERTA: We’re talking about something that would be a lot more watery. So, you could have a thousand kilometers of water on the surface of this planet - if you could find a surface to it at all.

GELLERMAN: Well, it’s very close to this sun that it orbits, right - so it would be very hot!

BERTA: Yeah absolutely, and that’s one of the really strange things about this - because the temperature is so high - you wouldn’t have water in any form that we would know it. You would have steam on the outside - that’s probably the closest kind of comparisons we would have is the outer atmosphere of this planet. You know, it’s about the temperature of a hot oven - so it could be where you'd bake a baguette - this is steamy, roasty oven - we know that.

But as you dive deeper into this planet - you start getting into much higher pressures and so the water takes on a very different form. You wouldn't have a liquid water ocean like on earth - you might have solid water but at very high temperatures - super fluid water… all of these very strange substances.

GELLERMAN: I heard it described as “hot ice.”

BERTA: Yeah, that would be one way to describe there.

GELLERMAN: So, if I were to travel there, what would it look like? What would I see?

BERTA: I don’t really know. Frankly, I’ve had a lot of trouble kind of imagining what this planet is like and part of that is because there still is a lot that we don’t know about it.

GELLERMAN: How do you know anything? You mentioned the Hubble space telescope…

BERTA: Yep, so we watched the planet as it passed it’s star as seen from earth. And a tiny fraction of the star’s light will filter through the planet’s atmosphere before getting to us, and so we can measure the color of that light that has traveled through the planet’s atmosphere before getting to us. The analogy that I like to make - and I think this is actually a pretty good one - is that imagine you’re standing on this planet - and watching a sunset, the most beautiful sunset. And it has some color to it. And you could imagine if the atmosphere were different, that color could be very different, right?


BERTA: But now imagine the light that passes over your shoulder - doesn’t come to your eyes, but passes on through space for 40 years and then gets to our telescope. With the Hubble space telescope we can measure that sunset on that planet.

GELLERMAN: That’s almost romantic!

BERTA: Yeah, I think so.

GELLERMAN: GJ12-14b, where does that romantic name come from?

BERTA: It’s a beautiful name ! So in astronomy, we have a tradition of naming bodies that orbit other bodies, after them. The star has the number GJ12-14, so if you find something orbiting GJ12-14, you have to call it GJ12-14b.

GELLERMAN: So you couldn’t name it something like “Big Berta.”

BERTA: (Laughs.) Um, no. Actually my advisor’s wife is first in line for the planet names. But it’s a problem that we have - at some point there are going to be a few of these planets that are so interesting to us that we really do want to give them interesting names that make them, you know, easier to remember.

GELLERMAN: Now would you be surprised if it turns out it’s not this weird water world but something weird like blue cheese or Styrofoam?

BERTA: I wouldn’t be that surprised.

GELLERMAN: (Laughs.)

BERTA: Well, I would be a little surprised if it were blue cheese. There’s still so much we don’t know about many of these planets, and so a lot of the conclusions that we draw from them are based on our modeling and our understanding of the physics going on on these planets and a lot of what we say is guided by what we know about the universe as a whole. In particular, what we know about the abundance of various elements in the universe - and that’s something that’s fairly well constrained, so that’s something that is a good predictor of what planets will be like.

GELLERMAN: The Hubble has really been a tremendous tool to astronomers.

BERTA: Oh, absolutely.

GELLERMAN: It’s been up there since 1990, am I right?

BERTA: Yeah.

GELLERMAN: But it’s supposed to be shut off in about two years…

BERTA: Well, I think that Hubble is going to keep going as long as it can. With the end of the shuttle program, there will be no more repair missions, which is something that has made Hubble so useful, is that you can keep upgrading it as they years go by. So without the shuttle, at some point, sadly, the cameras will stop working and things will start to fade away on Hubble.

GELLERMAN: Are there plans for a post-Hubble telescope?

BERTA: Yeah, and so that’s something that we’re all really excited about. So, that’s something that’s called the James Webb Space Telescope, which is like Hubble but bigger and better. It’s going to be far away from Earth, and it’s going to be observing at infrared wavelengths, which is great because that allows you to see back to the beginning of the universe- there’s all this incredible astronomy you can do with it. The thing that I’m most excited about with it is that you can study the atmospheres of planets, and specifically- study the atmosphere’s of planets that are not necessarily these weird things like GJ12-14b, but planets that could be a little bit cooler and a little bit smaller, and could, conceivably, be host to life.

GELLERMAN: What’s interesting about science in general, and astronomy in particular, is that the more you learn, the weirder it gets.

BERTA: The thing that makes me really excited about, I guess, as you say “the more we learn, the weirder it gets,” is that we’re at this really interesting place right now where we only just now have the technology to find planets like these and to observe planets like these and to study their atmospheres. To really study what’s out there - it makes me really excited to think about what surprises are around the corner.

GELLERMAN: Well, Zachory Berta, thank you so much for coming in.

BERTA: You're welcome, my pleasure.

GELLERMAN: Zachory Berta is a grad student astronomer at the Harvard-Smithsonian Center for Astrophysics.



Harvard-Smithsonian Center for Astrophysics

Zachory Berta


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