Sensing the Atmosphere of Distant Planets Scientists using the Hubble Space Telescope have been able to detect the chemical signature of methane in the atmosphere of a planet orbiting a star 63 light-years away. It's the first detection of an organic molecule around a planet outside the Earth's solar system.
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Sensing the Atmosphere of Distant Planets

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Sensing the Atmosphere of Distant Planets

Sensing the Atmosphere of Distant Planets

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A bit later in the hour, personal privacy online. But first, astronomers using the Hubble Space Telescope have managed to detect the presence of water and methane in the atmosphere of a planet orbiting a star 63 light-years away. Now, "E.T." probably won't be phoning home soon from there, because it's a hot gaseous planet that's unlikely to be able to support life. But the ability to detect organic molecules in its atmosphere from so far away should be a big boost to the study of so-called extrasolar planets - planets outside of our solar system.

Joining me now to talk about the work, which was published in the journal Nature this week, is Mark Swain. He's a research scientist and deputy director for J.P.'s Exoplanet Center of Excellence at NASA's Jet Propulsion Laboratory in Pasadena, California. He joins us today from a studio.

Welcome to program, Dr. Swain.

MARK SWAIN: Thank you very much. It's a pleasure to be here.

: Scientists must be pretty excited about this, yeah?

SWAIN: Oh, absolutely. The - part of the excitement is that this is a dress rehearsal for the future searches that we hope to do for life on more hospitable planets.

: Mm-hmm. What is so special about this discovery?

SWAIN: Well, there has been a great deal of theoretical work about what molecules and, in fact, chemical processes may be going on in the atmospheres of these exoplanets, that's what astronomers call these planets around other stars.

: Mm-hmm.

SWAIN: But until very recently, the ability to detect any of these molecules really hadn't been demonstrated. And last summer, there was a big success with detecting water, and now that methane has been added to that list, that's very exciting and, again, the potential significance of methane on more hospitable planets for some sort of association with biological activities...

: Mm-hmm.

SWAIN: interesting.

: So where you have methane, you might have some possibility of creating that primordial chemical stew of soup that might lead up to chemical evolution of life?

SWAIN: That's right. Methane is identified as one of those potentially prebiotic molecules.

: Mm-hmm.

SWAIN: So under the right conditions and with some other molecules - like ammonia and water and hydrogen - methane can participate in the synthesis of some types of amino acids, which are of course the building blocks of life.

: Mm-hmm. Did people actually observe the planet itself somewhere out there in that solar system?

SWAIN: Well, we observe it in a rather indirect way. So this planet has a very fortuitous orbit, the orbit of the planet takes it right in front of its parent star as we view the system. And the way we made these measurements is we waited until the planet was just about to cross in front of the parent star, and we started taking measurements. And we watched this event, which astronomers call the transit. And during the transit, the planet blocks a little bit of light from the star. During that blockage, a little of the starlight filters through the planet atmosphere and we're able to study that light and find the fingerprints of molecules in the exoplanet atmosphere.

: Mm-hmm. So it - does it have to be just the right planet in the right spot? If you see something...

SWAIN: Well, it certainly has to have the - for this technique that we used, the planet has to have the right orbit configurations, so it needs to be a transiting exoplanet.

: Mm-hmm. And how about adapting this to other exoplanets?

SWAIN: Well, certainly, there are other transiting exoplanets, that we could do the same experiment on, and we're very excited about that. We could do about - we think about six exoplanets right now with similar levels of sensitivity.

: Mm-hmm.

SWAIN: In the long term - that being, you know, on two or three year timescales - we hope to expand this technique to perhaps start to include non-transiting planets.

: So what would really get you excited? If you - what kind of planet - if you saw the methane, if you saw the water, would it have to be a planetary system just like ours, with the planet the same size of ours for you to really be jumping up and down?

SWAIN: No. For me, jumping up and down would be some sort of planet which is going be a smaller than a gas giant, but it would need to have a surface. So it could be a water world, it could be a super Earth, it could be bigger than Earth, but it would need to be in the habitable zone. And this is the zone around a star where water can exist in liquid form. And if we were to see methane from a planet like that, then we would be very excited.

: Mm-hmm. 1-800-989-8255. Let's take a few phone calls here. Let's go to Armando(ph) in Galena, Illinois. Hi.

ARMANDO: Yes. Good Afternoon. How are you doing?

: How are you?

ARMANDO: I would like to know how distant(ph) the universe is. Because you are talking about this planet that is about 63 light-years from the Earth. And within one light-year of the Earth, how many solar systems are there, more or less?

SWAIN: Oh, the - there are not any other solar systems one light-year from the Earth. So the nearest star is about is three light-years away. And there are some exoplanets that are - let see, 15 or 20 light-years away, and that's quite close by exoplanet - I mean, by both astronomical and exoplanet standards. But nothing is close as a light-year.

: I have a couple of questions from "Second Life," they're related, so I'll ask them both at the same time. Ozzy Mandius(ph) and Namie(ph) ask about the presence of oxygen in the atmosphere of these. Can we detect oxygen, one wants to know, and the other one wants to know ozone - will the presence of ozone be a good indicator of Earth-like life?

SWAIN: Yeah, those are really good questions. And certainly, ozone and oxygen in the form of O2 have been talked about as potential indicators of life. With the instrument that we use on Hubble, we're not able to detect those. So the fingerprints of those molecules, O2 and O3 - which is ozone - show up in different places than the wavelengths we covered.

: Mm-hmm. So what do you do now? Do you just keep looking for more exoplanets there with Hubble?

SWAIN: Well, the thing I'm really excited about in terms of the next step is trying to localize the measurements to different regions in the atmosphere. And so if we - for these transiting systems, we can use the transit to observe the light as it filters through the atmosphere and that probes the atmosphere at the terminator region, that junction between day and night.

: What surprises me - I mean, I've been covering astronomy from many years, but the idea that you can look at a planet in a solar system that's 60 or so light-years away and fine tune what you're looking at in that - which part of the atmosphere are you looking at is just mind-boggling to me.

SWAIN: Well, if we observe the same system in the - what's called the secondary eclipse when it goes behind its parent star, we can - in principle - extract the dayside emission spectrum. And in fact, we're working on this right now. And then by comparing the types of molecules we find and the abundances of those molecules, we can start to look at how the chemistry may change from the dayside going towards the nightside. And so that's - for me, that's the next step on...

: Wow. And what would that tell you?

SWAIN: Well, one of the - our questions is the atmospheric chemistry dominated by what is generally called thermochemical equilibrium, or does photochemistry, do the photons of the star have an important chemical role beyond just heating the atmosphere. And so, that's a bit more esoteric, but it's - it is a significant question for understanding the chemical processes that are present in these atmospheres.

: Are you saying that the energy given by the sun might create reactions, chemical reactions in the atmosphere?

SWAIN: Yeah, it certainly could. There could be, there could be photocatalyzed reactions or photolysis of some molecules, and that's really what we're wondering about. We don't know the answer to that yet.

: Yeah. But what molecules would they show up as?

SWAIN: Well, when the - what we're hoping to do is measure the change and abundance of methane, and perhaps some other molecules - if we succeed in detecting them as well, and if those abundances don't square with what we'd expect from a thermochemical equilibrium, we might infer that there are some photochemistry going on.

: Mm-hmm. And how soon do you think you could do that?

SWAIN: I think this is going to be, these results will be coming out over the next four, five months.

: For - why so long? I mean, you're looking at the, you know, the star now, I suppose.

SWAIN: Oh, with the - we have the data and, in fact, we're working on it now. The way the scientific process works is that papers need to be reviewed. And so, we would - you know, we would normally announce significant progress, progress only after a paper is accepted. And so, we do have to give time for the review cycle.

: Is the Hubble Telescope the main observing telescope for exoplanet?

SWAIN: Well, not at all. The Spitzer Space Telescope has, you know, over the last two years been delivering a string of very dramatic results which, frankly, revolutionized the characterization of exoplanets. So Spitzer made the first detection of light emitted by an exoplanet and there was a long series of follow-up observations.

: So, you guys sort of sneaked in on this one?

SWAIN: Hubble is not really new to the game.

: Yeah.

SWAIN: Hubble had an initial discovery of an exoplanet atmosphere back around 2000, 2001. But it hasn't - Hubble hasn't had the center stage in the exoplanet characterization game lately.

: Can we actually see this planet? If we went to the Hubble's site on the Web, can we see this planet?

SWAIN: You might be able - you can certainly get an image of the sky from - there are any number of star catalogues, but you would not be able see the planet. It's so close to the parent star that current instruments can't make an image that shows the planet as a little separate dot.

: But you're still able to just see right into its atmosphere?

SWAIN: That's right. And we do that because we know the timing of this orbit very well. Every time this planet crosses its parent star, it blocks about 2.4 percent of the starlight. And people have studied that and looked at repeated observations. And so, we - there's this very definite period. So astronomers can solve the orbit.

: Yeah, fascinating. Dr. Swain, thank you for taking time to be with us.

SWAIN: Thank you very much.

: Mark Swain, research scientist and deputy director for JPL Exoplanet Center of Excellence. JPL, that's NASA's JPL laboratory in Caltech, out there in Pasadena.

We're going to take a short break, come back, change gears and talk about privacy. A lot of news today about invasions of privacy online and how can you take steps yourself. What should you know about it. Stay with us, we'll be right back after this short break.



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