Astronomers Discover New Exoplanets
IRA FLATOW, host:
This is Talk of the Nation Science Friday. I'm Ira Flatow. Later in the hour, we'll discuss controversial new research on cholesterol-lowering drugs. But first, if you gaze towards the southern skies at night, one of the brightest stars in the sky might catch your eye. It's burning 16 times brighter than our sun called Formalhaut. Great star. It's one of the - our closest neighbors. It's about 25 light years away. And back in the 1960s, the classic fantasy and science fiction author, Ursula K. Le Guin, wrote of an imaginary planet called Formalhaut II. But you know how these days science fiction happens - just happens to turn into science fact?
Well, this week in the Journal Science, a group of astronomers reported the discovery - not of Le Guin's Formalhaut II, but a planet they called Formalhaut B, a bona fide planet orbiting the bright star Formalhaut. They say that the exoplanet is no more than three times the size of Jupiter. Now lots of exoplanets have been discovered before, but what makes this discovery special is that astronomers were able to take a snap shot of the planet with a camera in visible light, in ordinary snapshot. Now that has never been done before, albeit this was a camera attached to a very big telescope, one aboard the Hubble Space telescope.
Here to talk about it is James Graham, a professor of Astronomy at the University of California at Berkley, a member of the team that took the picture. If you'd like to talk about it with us, our number is 1-800-989-8255, 1-800-989-TALK. We're also twittering. If you like to twitter with us on Science Friday, you write the @-sign followed by scifritter. That's S-C-I-F-R-I-T-T-E-R. And in Second Life, we're also hosting a discussion there. You can join us in Second Life. Welcome to the program, Dr. Graham.
Dr. JAMES GRAHAM (Professor of Astronomy, University of California at Berkley): Hello. Thank you, Ira. Good to be here.
FLATOW: How are you? You must be pretty excited.
Dr. GRAHAM: Oh, this is a tremendously exciting time for astronomers. Certainly, it's a Golden Age for Astronomy, not just for discovering exosolar planets, but for understanding cosmology in the universe at large.
FLATOW: Explain to us how you found Formalhaut B.
Dr. GRAHAM: So the problem regarding finding these exosolar planets, at least taking pictures of them, is that they're tremendously faint. This particular object turned out to be three billion times fainter than Formalhaut itself. And so the problem is again, defining the firefly next to the search light. So we require exceptionally good optics, very well-crafted cameras and then careful analysis of the observation after the pictures have been taken.
FLATOW: And we have a picture of it up on our web site on sciencefriday.com if our listeners want to look at it. And I'm looking at it now and two things strike me. One is, where did the star go in the picture? It's not there.
Dr. GRAHAM: Right. So this picture you may have seen before as my - some of my collaborators, Paul Kalas and Mark Clampton(ph), picked - published the picture of what's maybe been referred to as the evil eye of Sauron in some of the popular literature. And so these are images taken with the instrument configuration on the haut - part of the coronagraph. And the coronagraph is a fancy name for an occulting spot that's in the camera, that blocks out the light from the stars. So right at the center where the pupil is of the eye, is where the star lands. So it's behind the occulting spot.
FLATOW: And because it would be too bright, right? It would sort of blind the telescope.
Dr. GRAHAM: Precisely. So as you mentioned in the introduction, Formalhaut is about 16 times more luminous than the sun and this planet. We believe is actually the faintest known object outside the solar system. It has a luminosity of two tenths of a million that of our sun.
FLATOW: Now, I would imagine though that one of the reasons you could see the planet and that dot in the picture is because the star, though, was so bright.
Dr. GRAHAM: Oh, yes. The - some of the light that we see from the planet itself, we believe is actually reflected light. And there are various techniques for finding planets. There are planets found indirectly using Doppler methods where you see the wobble imposed on the star by the orbital motion. And you can look for reflected light, which requires a bright - you can look for self-luminous planet, which is actually a technique used in a second paper that came out in science this week, describing a three-planet system. So this really is a bonanza week for the discovery of exosolar planets.
FLATOW: And so this is really the first picture of a planet like we might take a snap shot of it with our own if we could.
Dr. GRAHAM: This is certainly - it satisfies those criteria. It's an image in visible light, so you could imagine being a super-evolved creature being able to look at Formalhaut and actually see it with your own eye, which is one of the things that stimulates the imagination here.
FLATOW: It is very exciting, but I'm having trouble. I look at that picture. I see lots of little dots that I would call blots in there.
Dr. GRAHAM: Oh yes.
FLATOW: How do you know which one is a real planet?
Dr. GRAHAM: So in looking at the pictures, you see this radial structure just beyond the black dot. That's the structure that looks like the iris and that's a pattern that's associated with optical errors in a Hubble telescope. It's called the speckle pattern. And so what we have to do is measure that pattern very carefully. And we do that by looking at other star systems. For example, other stars of the same type that have approximately the same brightness, like Vega. And we compare that speckle pattern of the speckle pattern in Formalhaut. And then the difference, allows us to see objects that are associated with Formalhaut. So it's a differential comparison of multiple stars.
FLATOW: So did you take time laps over a period of years, too, to see if the planets moving?
Dr. GRAHAM: And if you inspect the image, you'll notice that there are other objects in the field. These objects are very faint, so many of that objects in the field are background galaxies. There are also some background stars with their own within our own Milky Way and so to be able to distinguish those sources from something that's physically associated to Formalhaut, we have actually looked for the orbital motion of Formalhaut planet around it. So we have to look at multiple epochs. And currently, we have two epochs and we can see the object move. That's the - it was essentially for us the clincher when we saw this object physically associated with Formalhaut.
FLATOW: Why did you choose this star? Did it match what a model you thought that you could actually take a picture of?
Dr. GRAHAM: So Formalhaut - from the point of view of planet hunting - became a hot target in the 1980s. In the 1980s, the star was discovered to have a system called a planet debris disk. That's a cloud of dust, orbiting the star and believed to be the remnants of material leftover from building planets. And so ever since then, Formalhaut has been studied, and in fact, this image that we published three years ago - the first version of the evil eye picture was the first resolution of invisible light of that debris disk. And once we saw the structure there, once we saw the polar dot in the edge of that belt, we were pretty confident that there must be something in there responsible for sculpting the belt. And in fact, one of our colleagues, Alice Clowin(ph) in New York predicted the location of the planet. Last year, she predicted the location of a planet - of a separation of a 119 astronomical units. And so that's remarkable insight in our current calculations, especially by Eugene Chang, have shown that that's very consistent with what we see.
FLATOW: Are you going to be taking other pictures of it? Can you magnify this anymore at your maximum resolution?
Dr. GRAHAM: So you could imagine - with two epochs, we're excited. What we really came to do is to see a third epoch of the Hubble Space telescope. So you can bet we will be biting our nails when service ignition 4 goes next year and prepares the Hubble to observe again for this target.
FLATOW: Is it possible to use any other telescopes besides the Hubble on something like this?
Dr. GRAHAM: Indeed yes. So the other technologies that are developing to help us see exosolar planets from the ground is called adaptive optics and we'll be using that (unintelligible) telescopes like the Gemini Observatory and the Keck telescope.
FLATOW: Are there other stars that seem like good targets too.
Dr. GRAHAM: Oh, yes. There are very interesting long lists of stars with known debris disks. Many of them are brand-named stars like the bright star in the southern constellation of Beta Pictoris is another excellent candidate that has a debris disk. And we will be looking at that system very closely.
FLATOW: Now, if I wanted to go out tonight and see Fomalhaut, where would I look in? Are there any guide points in the sky for it?
Dr. GRAHAM: One of the ways that makes it easy to recognized Fomalhaut, it's a southern star, so look in the south. You have to look fairly early in the morning these days to see Fomalhaut. But it's a very isolated star. It's the only bright star in the southern sky early in the morning these days.
FLATOW: Wow. So that should be sitting right by itself.
Dr. GRAHAM: That's correct.
FLATOW: And I would imagine you have spurred other astronomers on now.
Dr. GRAHAM: There has been tremendous response from the community and a great of excitement. And there are various missions being planned by NASA and by ground-based observatories to search for exosolar planet using imaging techniques. And we're very excited about the momentum that just adds to that effort.
FLATOW: Is there any way to see if there is any atmosphere or anything like that on this planet or would you know that already?
Dr. GRAHAM: Our knowledge of the physical conditions on this planet at the moment are exceptionally rudimentary. We can guess what the temperature is. It's probably something like the planet Neptune in our own solar system even though this is a luminous star. The planet is remote from the star, but rather cool. But it will require a great deal of effort to collect the data to study its atmosphere. And that would require things like 30-meter telescopes and the successor to the James Webb telescope but there's (unintelligible) Hubble telescope with the James Webb telescope.
FLATOW: You mentioned in the other paper in science about the infrared radiation in the other planets.
Dr. GRAHAM: That's correct, yes.
FLATOW: Can you give us an idea what those planets might be like?
Dr. GRAHAM: This is a system with a name that is not quite so euphonious as Fomalhaut. It's called HR 8799. HR stands for Harvard Revised Catalog and has been discovered there is heat radiation left over from the formation of these young objects and by interpreting the observed luminosity, you can estimate once you know the age of the system that these objects are fairly massive. They probably have masses maybe that run ten more than Jupiter.
Dr. GRAHAM: But what's remarkable in this system is the fact that there are three objects and the orbital motion has been discerned in the discovery of the (unintelligible).
FLATOW: All right. Dr. Graham, we'll have to pick that up later but I want to thank you for taking time to be with us. Fascinating and good luck to you.
Dr. GRAHAM: Thank you so much.
FLATOW: James Graham, professor of astronomy at the University of California in Berkeley talking about the first picture of an exosolar planet. We're going to take a break and come back and talk about controversial health study about Crestor. So stay with us, we'll be right back.
FLATOW: I am Ira Flatow, this is Talk of the Nation Science Friday from NPR News.