Jo Pitesky: Welcome to NASA's PlanetQuest Podcast, Episode 6. I'm Dr. Jo Pitesky.
Since 1995, when the first planet was discovered orbiting a star other than the sun, almost 200 new planets have been found. This onslaught of discoveries has re-written astronomy textbooks and toppled some longstanding theories of planet formation. It has also lead to a renaissance of interest in one of science's oldest and most basic questions: "Are we alone?" The possible answer to that question lies with a new fleet of spaceborne telescopes specifically designed to search for planets like Earth and the chemical traces of life. Here today to talk about that ambitious program is Wesley Traub, chief scientist for NASA's Navigator Program, also know as PlanetQuest. Dr. Traub, welcome.
Wesley Traub: Thank you.
Pitesky: Briefly, what are NASA's planet-finding goals over the next decade?
Traub: Well, NASA's been in the planet-finding business for a long time. This is not something new. So the plan for NASA in the coming decade is basically to follow up on all these discoveries of basically 200 planets that we know about today. The main thing we'd like to know is, are there any other planets out there that look like the Earth? The focus of NASA's program for the coming decade, basically, is to find the planets, find how frequently Earth's are found around stars nearby, find which stars have Earthlike planets, or if they don't have them, find why not, and then to actually look and see if we can measure an Earthlike planet around a star and determine if it really is Earthlike.
Pitesky: Let's talk about some specific missions. How would something like the SIM PlanetQuest mission be unique or do something different in terms of trying to locate some of these planets?
Traub: Okay, good. The purpose of SIM PlanetQuest is to look for all sizes of planets around nearby stars. So that's a key thing, it looks for many different sizes and that range of sizes goes all the way out to these heavy Jupiters all the way down to a single Earth and it has the capability of finding Earth-mass planets. Nearby stars are of interest because we can see them, they are our neighbors, and more importantly we can follow up with later missions that would actually focus on these stars with a telescope of some sort, and isolate the light of the star, the really bright light of the star from the faint light of the planet, so we can characterize planets and see if there's life.
Pitesky: So what happens in the future after SIM PlanetQuest? How does SIM set the stage for possible more advanced planet finders in the future?
Traub: SIM will tell us whether there are Earthlike planets around nearby stars and that will be a big step. It will tell us whether there are Earth-mass planets near the star and what orbit they're in, which well tell us how close or how far away they are from the star. So it tells us these two crucial things. Mass of the planet and where it's located in respect to the star how far away it is. If we know the mass and we have a mass that's in the neighborhood of one Earth mass, we know we have a candidate here. And the other thing SIM will do is, as I said, is to tell you how far away it is from the star, which is crucial. If it's too close to the star it'll just feel the heat and be hot. If it's too far away it'll feel cold, so in between there's the region called the habitable zone, which is the condition we find on Earth in our solar system. This zone goes from Venus, which is 70 percent as far from the sun as we are to Mars, which is one-half as far from the sun as we are, so there's a fairly wide range where people think you can have a habitable condition. Which means water. So SIM will tell us whether or not this planet is in the right range (the habitable zone) from the star to have liquid water on the surface. If you want look for a place that's Earthlike, it'd be good if you had water.
Pitesky: So SIM is going to act as a precursor and look for planets where we could then narrow in and find something that could be "Earthlike."
Traub: Absolutely. If SIM finds these things we'll have a list of targets. We'll know exactly where and when to look with succeeding missions, which maybe we should talk about. There are two missions planned after SIM: one called Terrestrial Planet Finder Coronagraph, and the other called Terrestrial Planet Finder Interferometer.
The main thing that these two missions will do is to not only check if SIM gave the right informatioin and find the ones SIM couldn't find, it'll characterize the planet. It'll tell us whether or not the light that comes from the planet is similar to the light from Earth or from Jupiter, whatever. We look at the color of the light, the spectrum of the light, and we can tell what the basic planet is really like at heart.
Pitesky: So how did you get started in this field? What is your background?
Traub: My background is, well basically I'm interested in looking at the spectra of things. I like the idea of learning about an object by not actually touching it, but being back a mile to 100 miles, 93 million miles to, quote, the sun. And I just think it's fascinating that you can tell all about an object just by looking at its colors and spectrum and you can sit quietly in your lab or whatever and anyone can do this with a telescope or their eyes and you can learn something about these distant, far-away objects.
Pitesky: When did this start? Was this an interest that started when you were a child, something someone said, a book you read, a TV show? What sparked it all?
Traub: I've just always been interested. I remember as a child I was 12 years old or something. Fiber optics were new at the time, so I made up this letter, now in retrospect I think that I must've been completely seen through. I made up this letterhead as if I were a company and I wrote off for a free sample for some fiber optic thing and lo and behold they actually sent it to me in the mail and the people at the other end were probably giggling when they sent it, and said we know what he's doing, but you know, I though I was fooling somebody. It was great.
Pitesky: It must strike you every once in a while that you have a really interesting job. Looking for life on other planets, coming up with missions to find planets, something we couldn't envision a decade ago as being a job that you could actually be hired to do.
Traub: You're right. It's actually the most exciting thing I could think of to do. Actually when I came here to JPL about a year ago people said, why are you moving? I mean I moved from Boston, my family is still there, my house is still there, I'm here. I explained, you know, this is the most exciting thing I could think of to do in three lifetimes. There is going to be no other point in history when we can discover an Earthlike planet and where we can tell if there's life on it, this will never happen again.
Pitesky: Dr. Traub, it's been a pleasure. Thank you so much for coming in and speaking with us.
Traub: You're entirely welcome.
