A Bounty of Planets in a Tiny Patch of Space

IRA FLATOW: This is Science Friday. I’m Ira Flatow. This week, you may have been lucky enough to observe a rare celestial occurrence and that is the transit of Mercury across the Sun. And as Mercury sailed past the Sun, it blotted out a tiny bit of the Sun’s light. You know, it’s so small it appeared like a black dot of like a period slowly pushing its way across a great ball of light.

Well, that same idea– observing a planet as it passes the face of its star– happens to be one of the key ways we detect exoplanets too. These are planets outside our solar system. And this week, scientists from NASA’s Kepler mission announced a huge new hall of planets. 1,284 exoplanets– huge, as we say today– added to our roster of known worlds beyond the solar system, which makes a total of over 30 to 100 planets we know of out there in the great beyond.

So next time you look up in the night sky, instead of seeing just stars, you might do as my next guest does and imagine each of those stars as a solar system. A whole solar system instead. Natalie Batalha is Kepler Mission Scientist at NASA’s Ames Research Center in California. Welcome to Science Friday.

NATALIE BATALHA: Thank you so much. It’s a pleasure to be here.

IRA FLATOW: How exciting is this?

NATALIE BATALHA: It’s been a great week. Yeah. And it’s been a long time coming. We’ve been working on this methodology and this paper for several years. It’s a methodology that’s been in the works for a long time.

IRA FLATOW: So it looks like there are a lot more of them out there than we ever thought or believed?

NATALIE BATALHA: Exoplanets, you mean?

IRA FLATOW: Yeah.

NATALIE BATALHA: Yeah, absolutely. As we look at these discoveries that are rolling in from Kepler and we crunched the numbers, we quickly realized that every star out there has at least one exoplanet orbiting it.

IRA FLATOW: And Kepler was looking at just the tiniest patch of sky.

NATALIE BATALHA: Yeah. You hold up your hand outstretched, kind of like a police officer saying stop, the size of your hand, outreached hand is about the size of the sky that we’re looking at. So it’s 10 degrees by 10 degrees on the sky.

IRA FLATOW: So if you were to extrapolate those results to the whole galaxy, how many planets might be out there?

NATALIE BATALHA: Oh, we’re talking billions. We’re talking tens of billions. Even if I isolate the population to really the ones that we’re very interested in– those that could potentially harbor life, as we know at least– that number is in excess of 10 billion in our galaxy alone.

IRA FLATOW: I’m just blown away by that number. Wow. Wow.

NATALIE BATALHA: Yeah. It tells us that there’s a lot of possibility, right? And of the planets that we have found, the diversity is so great. We’re finding worlds that we couldn’t have imagined before. Maybe George Lucas could’ve.

He had the world Tatooine or you have the planets orbiting two stars instead of one. We’ve got lava worlds. Just an enormous diversity. Planets that we don’t see in our own solar system. So nature is quite grand.

IRA FLATOW: I’ll bet. And now is capable of Kepler basically on a census mission trying to get a tally of all these different kinds of exoplanet?

NATALIE BATALHA: That’s right. We’re taking a census of sorts. It’s like calling up 1,000 people and finding out who they’re voting for and extrapolating that to the larger population.

We’re surveying about 200,000 stars, looking at the planets that are orbiting them, at least within what we call one astronomical unit. Kind of an earth orbit and inward. And then trying to understand, based on those results, what the population of planets is in the galaxy.

IRA FLATOW: These new planets we’re talking about, the 1,200 new planets, they were actually spotted a while back, right?

NATALIE BATALHA: Yeah. We saw evidence of their existence in the periodic dimmings of light that we observe. But when we see those tantalizing signals in the data, we don’t jump the gun. We call them planet candidates. And the reason for that is because there are astrophysical signals in nature that can mimic these periodic dimmings of light. And so we have to do due diligence, we have to weed out all of these potential imposters in order to really say that this is a bonafide planet.

IRA FLATOW: And one of the interesting things in all your data of planets is that there is a real abundance of planets that seem to be between Earth and Neptune size, something that we don’t really have in our solar system, do we?

NATALIE BATALHA: Yeah. That’s exactly right. So in our own solar system, we’ve got the small, rocky worlds, what we call the terrestrial worlds orbiting close to the sun. We’ve got the gas giants orbiting far away. And the leap in size between those populations is like a factor of four, right? Earth being kind of the biggest thing among the terrestrial planets at one Earth radius. Neptune would be the next. That’s four times bigger than Earth.

And so in between we don’t really have anything in our own solar system, or at least we don’t think we do. I’ll be a little mysterious there. But yet, the most common–

IRA FLATOW: Say that again.

NATALIE BATALHA: Well, I was alluding to the possibility of planet 9 in our own solar system. Looking at the gravitational perturbations of the Kuiper belt objects, and maybe that’s an indication that there’s another planet out there and maybe it’s actually fits in between sizes, something in between Earth and Neptune. I don’t know. Time will tell. But these kinds of planets in that size range are actually the most common planet known to humanity right now.

IRA FLATOW: What planets out of this latest batch are your favorites? Which do you think might be the most interesting?

NATALIE BATALHA: Oh goodness. Well, I’m intrigued by the lava worlds, I’m intrigued by the photo disintegrating planets that we see. Planets that are literally breaking apart before our eyes. They’re emitting these huge cometary-like tails. Might give us an opportunity to sample exactly what planets are made out of. So I’m intrigued by those.

I’m intrigued by these super-Earths, or what we call sub-Neptunes. This in-between region that you talked about. I’m also very intrigued by the oldest planets that we are finding.

There are planets in the Kepler catalog that are as old as the galaxy itself. And that, to me, was a very surprising result, because when you think about the building blocks that are required to construct a planet, it wasn’t really obvious to me that those building blocks would be available when the galaxy was in its infancy. But yet, here we’ve got these planets, and I’m intrigued by the idea that there are planets out there that are twice the age of the Earth, and I wonder, given that much time to evolve complexity and evolve life, what are the possibilities?

IRA FLATOW: No wonder you just can’t go out and look at the sky and just look at a star anymore.

NATALIE BATALHA: It does attempt to change one’s perspective, that’s right.

IRA FLATOW: Is the ultimate goal to find life or is it just to understand the planetary formation, as you say. The history of the galaxy and so on.

NATALIE BATALHA: Both of those things are tremendously important and depending on what scientist you ask, you’re going to get a different answer. For me, certainly, my passion for science is driven by the search for evidence of life beyond Earth. And so NASA does have a kind of long-term vision, or roadmap, if you will, for doing exactly that. It’s one of the primary science goals of NASA’s Astrophysics Division, absolutely.

IRA FLATOW: And how could you not believe– you said they were tens of billions just in our own galaxy here. How could you not believe that somewhere, there’s going to be some form of life. It’s almost like a certainty.

NATALIE BATALHA: Yeah. You’re preaching to the choir. I believe that as well. If I have to use that word believe just as a hunch. It would be a terrible waste of space, of course.

But the reality is we don’t know. And we’ve got these Goldilocks worlds. These are planets where there’s the possibility that liquid water could pool on the surface, but that doesn’t tell you what fraction of those are truly habitable environments where there is liquid water and where life could flourish. My impression is that microbial life is going to be ubiquitous on these worlds.

Whether or not there’s additional complexity or intelligent life, I don’t know. Maybe that is even yet rarer still. But time will tell. We have to do this systematic methodical search in order to answer that question.

IRA FLATOW: Will the upcoming James Webb Telescope help us get a closer look at any of these?

NATALIE BATALHA: The James Webb Space Telescope is going to look at exoplanets, absolutely. It’s going to do something called transmission spectroscopy. James Webb– we want to feed James Webb some of these transiting planets that we have found. They’re very special for the following reason.

When you have a planet transiting across the disk of its star, some of the starlight is going to filter through the atmosphere of that planet, and in doing so, the atmosphere is going to leave a chemical fingerprint on the light that’s streaming through. And so the James Webb Space Telescope will be able to catch that light, spread it out into a spectrum and see those chemical fingerprints, and that’s going to tell us what those atmospheres are made out of.

Now, the big question is can it do that for potentially habitable Earth-sized planets, and there I’m kind of skeptical. I think James Webb is going to be really great at characterizing the atmospheres of the Neptunes the sub-Neptunes, and if we get lucky, maybe a smaller planet like Earth. But I think that remains to be seen. We’d have to get really lucky.

IRA FLATOW: Couple of listeners’ question. One tweet from Patrick Fire says, “Can your guest speak a little on how you determine the age of an exoplanet or the composition of it?”

NATALIE BATALHA: Yeah. Great question. We can do that by looking at the star itself. So we have a lot of information about the star. In some of these situations, we have what’s called astroseismic information. In the brightness measurements, we can see pulsations of the light that’s coming from the star.

Those pulsations are starquakes that are causing the light to vary at very high frequencies. And by analyzing those starquakes, you can actually get the fundamental properties of the star itself. And one of those fundamental properties is the age.

IRA FLATOW: Wow. There you have it. We want to wish you the best of luck in doing this. Dr. Batalha.

NATALIE BATALHA: Thank you so much.

IRA FLATOW: And the Kepler spacecraft itself– is it in good shape or is it having any problems?

NATALIE BATALHA: It’s doing fantastic. It was hobbling along–

IRA FLATOW: Had a hiccup.

NATALIE BATALHA: –for a little while. Yeah, it had a hiccup. It lost a reaction wheel. The engineers resuscitated it, and it’s been operating ever since. It’s taking data and has enough fuel onboard to last until about mid-2018, I think is the current projection. So it’s doing some great science.

IRA FLATOW: Natalie Batalha is Kepler Mission Scientist at NASA Ames Research Center in California.