Superstars of Astronomy Page 1 of 25 Debra Fischer, professor of astronomy at … · 2015-04-07 ·...

Superstars of Astronomy of 25 Debra Fischer, professor of astronomy at Yale University, Debra Fischer, professor of astronomy at Yale University,

leading exoplanet discoverer and researcher

www.Astronomy.com Page 1 of 25

Dave Eicher: Welcome to the Superstars of Astronomy podcast from Astronomy magazine. I’m Dave Eicher, Editor and Chief of Astronomy. Each month I’ll share the thoughts and research of the world’s greatest astronomers, astrophysicists, cosmologists and planetary scientists with you in these hour-long chats.

Superstars of Astronomy is brought to you by Celestron. From

your first telescope to precision observatory grade instruments, Celestron has the perfect telescope to suit your experience level and budget. You can find out more at Celestron.com.

I’m very excited to have a special guest for our fourth show that

we’ve done now, Debra Fischer. Debra is an astronomer and professor at Yale University, and as we know, there’s really no hotter cottage industry than exoplanets. There’s so much excitement and interest in them, so this is really going to be a special talk.

We now know of more than 1,800 exoplanets. Kepler has produced

an additional 2,900 candidates. The pace of discoveries is really dizzying. It’s one of those things when your talk mentions exoplanets you need to check week to week to make sure that you have the right number.

Debra, of course, is one of the world’s leading experts on

extrasolar planets, having discovered hundreds of them by measuring Doppler shifts and the spectra of their stars including the first known multiple-planet system that was discovered in 1999.

Debra’s analyses of spectra demonstrated that gas giant planets are

more likely to form around stars with higher metallicities. From 2003 through 2008, she led the international consortium to search for so-called hot Jupiters around metal-rich stars, and this led to the discovery of 30 exoplanets.

I’ve enjoyed knowing Debra for some years, and she’s always

impressed me with her expertise. She’s contributed to Astronomy in the past. So without further ado, Debra, thank you so much for joining us today.

Debra Fischer: Thanks, David. It’s a pleasure. Dave Eicher: Let’s talk a little bit, if we can, as we get started about your

background. What got you interested in astronomy to begin with?




Debra Fischer: Well, I think it was probably the first astronomy class that I took

when I was in college. It was sort of unsettling. I remember feeling how insignificant it seemed that the Earth was in the context of the entire, well, galaxy and then the entire universe beyond that.

So the scope of things was almost dizzying and, as I said,

unsettling to me. Then I remember the second punch was when I ordered copies of the Palomar Observatory Sky Survey from the Caltech bookstore. They came in three flavors. Each picture was the same part of the sky, but one was taken with a red filter, one was taken with a blue filter, and one was taken with a visible filter.

When I realized then how our vision of the universe is just through

this tiny little window of the electromagnetic spectrum, the visible wavelengths — and when I realized that our instruments, though, could move beyond that into radio wavelengths and infrared that it just was so exciting. I just wanted to learn more about this.

Dave Eicher: There’s so much yet to be discovered in the universe, and you’ve

played such a big part of that in the last couple of decades here. It reminds me of that book that Martin Harwit wrote years ago, Cosmic Discovery, in which he claimed that we know about maybe 20 percent tops of the kinds of phenomena in the universe as that kind of wakeup perspective call you got there.

Debra Fischer: That’s right. Absolutely. Dave Eicher: Where did that take you in your studies from there? How did you

get interested in extrasolar planets and everything you got into before that?

Debra Fischer: So then I studied physics and was thinking of going to medical

school, but I just got hooked on physics and the beauty of mathematics and the astronomy classes that I was taking, and I had the chance to do an observing project at Lick Observatory, which is on Mount Hamilton above San Jose.

It was just, again, another incredibly emotionally moving experience to go up there and see these domes peering up into the universe and to know there was no financial driver for this — that these were really just monuments to humankind’s curiosity about the universe. So again, this was just so amazing.




So then I went on and I ended up getting my Ph.D. in astrophysics from the University of California at Santa Cruz. And just as I was finishing up, the first exoplanet was discovered by the Geneva team, Michel Mayor and Didier — then postdoc, his postdoc — Didier Queloz.

In fact, my colleagues, Geoff Marcy and Paul Butler, confirmed

that detection, and within a year they had a few of their own planets that were detected to add.

So I was graduating as this happened. And I was just so lucky to be

invited to join the team with Geoff and Paul and Steve Vogt. Dave Eicher: That was in the United States. That was the very dawn of

exoplanetary research, and you were right in the midst of that there.

Debra Fischer: Yeah. It was amazing because — I like to remember back — it was

a time when the velocity curves that we were measuring weren’t disputed by astronomers, but the interpretation was. So, most of the talks that we gave would have to really try to convince our colleagues that these really were planets that were tugging on their host stars. Now we look back, and those are such easy pickings to discover.

Dave Eicher: There was really a lot of skepticism. Did that sort of come from the

very early non-discoveries from Allegheny Observatory years and years and years ago —?

Debra Fischer: Yeah. Dave Eicher: — that was a shadow of skepticism of some false positives, if you

will … Debra Fischer: Yeah, absolutely. There was a long history of close detections and

announcements of exoplanets that then on further inspection turned out not to be right. So it’s the correct thing for the community to be skeptical and to have to really be forced to be convinced that the interpretation is correct.

So our data I think, again, weren’t disputed. It was the

interpretation. And so there what we had going for us is that we knew that at some point when we had found enough of these Jupiters that orbit very close to their host stars, we knew that roughly one in 10 of them should transit in front of the host star




and block out some of the starlight. And when that does, someone measuring the brightness of the star will see it dim for a few hours and then brighten back up again in a very predictable way.

So our technique could provide our colleagues who measured the

brightness of stars with the exact time of a prospective transit. We didn’t know if the planet would transit the star, but we knew when. If the inclination or the tilt of the orbit was just right, we knew exactly when that would happen.

And so in 1999, two things happened. The first transiting planet

was discovered. This was a planet discovered first with the Doppler technique measuring the velocities of stars, and then again we gave the prediction to our colleagues who measured the brightness. So they confirmed it. So that was great; a completely independent technique.

And then the second thing that happened was some astronomers

said, “Well, if you find a multiple-planet system, then maybe I’ll be convinced.” In that year, 1999, we also discovered the first multi-planet system: three Jupiter-sized planets going around the star Upsilon Andromedae.

So I think after those two events, then there was a lot more buy-in

from the community. Dave Eicher: And the door was really wide open, and it was really an established

fact. That had gone back a number of years. We had the pulsar planet in 1992, but then 1995, 51 Pegasi, but then 1999 because of both of those techniques confirming and also the multiple system, that was really what really sealed it you think …

Debra Fischer: Yeah, absolutely. Absolutely. Those were huge. In thinking about

the pulsar planets, that’s such a puzzle to everyone. The astronomers heard about this. This is a neutron star, a star that has probably gone supernova, exploded, and then just a tiny little remnant of a core of the former star is left behind, and Alex Wolszczan at Penn State is able to measure the timing from the pulsar and figure out that there were three planets orbiting it. They were planets that are similar in mass to the Earth.

Now, those planets couldn’t have survived the explosion by almost

all accounts. So they were actually reforming after the star exploded, reforming in a disk that settled around the neutron star.




I often think looking back that that should have been the tipoff that told us, wow, planets are ubiquitous. They’re just incredibly common.

Dave Eicher: Because even in the twilight years of that star, if you will, or the

end of the life of that star, you have a new generation of planets born.

Debra Fischer: Exactly. So it tells you that this process of planet formation, which

we still don’t understand in great detail, is an incredibly robust process.

Dave Eicher: Of course our detection capability is not obviously what it will be,

we hope, if funding — we can wake people up to the importance of science here down the road a little bit — but we’re already getting a feeling since that first decade of discovery of some of the character of planets nearby us for the most part in the galaxy, and there are astronomy enthusiasts, amateur astronomers, that gee, there are planets everywhere. Look at the tiny patch of sky in the relatively limited range compared to the diameter of the galaxy’s disk of Kepler and look at the enormous numbers of planets there.

There are planets pretty much everywhere almost, aren’t there? Debra Fischer: Right. This field has gone from in 1992 speculating that perhaps

most stars did not form with planets and our solar system was really quite unusual to now knowing, to having evidence from Kepler, that almost every star forms with at least one and in general several planets, a complex planetary architecture. So that’s just night and day.

Dave Eicher: A dramatic sea change. It almost reminds me of the skepticism and

mythology of black holes 25 years ago and the change over the last generation of understanding that nearly all normal galaxies aside from dwarves have a black hole in their center.

Debra Fischer: That’s right … Dave Eicher: It’s almost in parallel to that. As someone who has been in the

central seat of extrasolar planet research, how has that really affected you to see this incredible change over the last decade and a half, two decades? It’s really been a revolution.

Debra Fischer: It really has. It goes back to the idea that I had when I took my first

astronomy class about the discovery really, the realization at a




visceral level that we were a tiny, little spec in this grand Milky Way galaxy and now to know that almost all of the other 400 billion stars in our galaxy alone were born with planets, have planetary systems.

So it’s quite humbling and also just magnificently exciting at the

same time. Dave Eicher: It really, really is. Of course there’s nothing magically special

about other galaxies that we can believe that a presumption that the 100 billion other galaxies that exist in the universe similarly have planets around their stars.

Debra Fischer: That’s right. Exactly. I think it was interesting to hear you talk

about the transition with black holes and to think about the transition with exoplanets, and I feel like we’re standing on the threshold of that sort of a change in the search for life elsewhere.

So it just amuses me to no end to think about the day when the first

tentative sign of life is found in the atmosphere of another planet and then going from there to a point where we have hundreds of thousands of examples. That will really change our sense of who we are in the universe.

Dave Eicher: And how do you think that will affect people? Because we’ve

fought so hard as a species to be centrists with everything here. That’s going to be a really profound moment when we do get evidence even spectrally, atmospherically that we believe there’s life on another planet. That’s going to be a moment that really shakes humanity, won’t it?

Debra Fischer: Exactly. I think it will. It will be very profound. Dave Eicher: That may be coming. It may not be terribly far off. Debra Fischer: It may not be so far away. I agree. I would be surprised if we don’t

have some kind of a tentative signature in the next decade. Dave Eicher: Really. Wow. Debra Fischer: Yeah. It could be years just with the James Webb Space Telescope,

which will be launched in a few years, and the other assets that we have in space.




This is actually very important. The reason we haven’t detected life elsewhere is because we don’t have the sensitivity to be able to detect it. That was the situation with exoplanets. They were there in enormous abundance, but we just didn’t have the instruments that were able to sense them.

And so that’s where we are right now in terms of finding exolife,

life elsewhere. It might be that there really isn’t anything else in the galaxy. I would find that very surprising, but —

Dave Eicher: Me, too. Debra Fischer: —- but we’ll get to the point where we can really figure out how

common life is. Dave Eicher: Now we’ve talked about hot Jupiters, and those are those easiest to

detect, the guys who came along really early because those are massive planets, gas giants and very close into their host stars because there’s also the issue of length of observation —

Debra Fischer: Exactly. Dave Eicher: — to detect things as well as size of planets as well. So there are

lots of those guys, but let’s talk about we’ve now heard many, many institutional press release writers talk about, “Well, we found other Earths.” We really haven’t found an Earth analog. We’ve found planets that are multiple times more massive than Earth but are much, much smaller than a Jupiter, but we’re really getting still to the point of finding Earth analogs, are we not?

Debra Fischer: We really are. It’s incredible when you look at a diagram that

shows the mass of a planet and the orbital periods and look at what we’ve discovered and how there’s a little box where planets like our Earth would be positioned at 1 Earth mass and at one year in an orbit. None of the techniques that we have are really able to penetrate down with the sensitivity needed to fill that box.

So when I look at the distribution of the types of planets that we

found and know that every indication that we have is that we’re seeing the tip of the iceberg and that, in fact, the most numerous type of planets are the small rocky planets. So where our vision or the lens through which we see exoplanetary systems is completely skewed.




Dave Eicher: So you’re saying there’s a real problem coming because if we think we have a backlog of data now —

Debra Fischer: That’s right. We have a lot of work to do. Dave Eicher: — It’s going to keep some people busy in the future. Debra Fischer: That’s right. We’re working at Yale to try and build instruments

that have unprecedented precision so that we’ll be able to find those kinds of planets. One of the arguments or points that I make is that we’re guaranteed a success. If we build the instrument with enough sensitivity, those planets are there in great abundance. So it’s a great situation to be in.

Dave Eicher: It’s exciting to have that compelling return out there, which is

highly unusual in the science. Usually you don’t anticipate something that certainly given what we know we believe about planetary — about solar system formation if you will.

Debra Fischer: Exactly. Dave Eicher: Well that’s exciting. Talk a little bit more if you would about

you’re involved in a number of current research projects that you’re directing and working on at Yale there involving a spectrometer at Cerro Tololo and some new instrument designs as you mentioned that will provide higher sensitivities and precision. You’ve got a lot going on there that you’re overseeing now, don’t you?

Debra Fischer: Definitely. I think starting in about 2007 I felt that people designed

instruments to achieve a certain goal, but radio-velocity precision wasn’t quite the metric for their instrument.

So one of the things that we did when I arrived at Yale was to build a Doppler diagnostic facility. I think I was able to finally merge my pre-med wishes with my astronomy background now. We’re actually looking at how all of the design choices that we make impact radio-velocity precision.

So we’ve learned a lot. I feel like we’ve conquered on several

fronts the technology that we need to be able to build an instrument that will provide us with the precision to detect Earths.

The one thing that stands in our way actually turns out to be the star itself because we’re not looking at just — I just saw these




beautiful images from the solar telescope showing the Sun with enormous flares rippling across its surface with electromagnetic radiation, bright spots, plumes.

So we’re looking at stars that are quite variable themselves, and

they provide noise, but that noise is not the same as the dynamical Doppler shift of a star as it moves towards us and goes away from us.

So we’re working right now on new statistical techniques to tease out tiny signals in the presence of time-correlated noise. We’re working on extremely high-resolution instruments that can distinguish again between the effect that the star spots and the star flows will have on the spectra.

I’m organizing a conference this summer, which will be held at

Yale, that’s going to bring together a community of 150 astronomers to a workshop to roll up our sleeves and figure out how we’re going to divide and conquer on all of the fronts that we need to be able to detect Earths.

Dave Eicher: Wow. Well that’s going to be a major milestone meeting it sounds

like. Debra Fischer: I think it’s going to be fantastic, yeah. Dave Eicher: Wow. Well that’s great. So we’re really getting close. How do you

see the funding for exoplanet research because there’s so much going on, so many resolves it seems, but of course the overall funding picture for, especially in the United States, for science and for astronomy research in particular is pretty weak right now?

Debra Fischer: Right. So I think for exoplanets, interestingly, this is a whole new

field. It’s become a priority for NASA. So NASA funding is in place, but the NASA mission is really for space-based astronomy.

So one of the things that’s happened is the radio-velocity measurements from the ground have sort of fallen through the cracks in terms of being able to secure funding. And that’s really a shame because this is how we’re going to detect, I think these, tiny, little signals from earth and because these kinds of measurements will make the space missions multiplicatively more efficient and productive.

Superstars of Astronomy of 25 Debra Fischer, professor of astronomy at Yale University,



But fortunately both the NSF and NASA have realized that. I think one of the first times ever they’ve come together, and they’re offering an opportunity to build a new spectrograph that will go at the WIYN Telescope in Arizona. So it’s a start. It’s always, always a struggle.

I think fundamental technology development is always tough. It’s

always been tough and it’s just because when you write a proposal you can’t say, “I’m going to do A, B, C, and that will give us this product.” Sometimes you don’t know. It’s blue skies. You’re exploring, and you’re figuring out ways of solving problems, and it’s hard to predict always how successful they’ll be.

Dave Eicher: And sometimes the most exciting results are unpredictable

beforehand. Debra Fischer: Absolutely. Dave Eicher: Well it’s good to hear that the WIYN is going to be involved with

it because they’re sort of searching for new roles for instruments that Kitt Peak it seems like.

Debra Fischer: Right. So I think this is really fantastic. I was on the NSF Portfolio

Review Committee, and at the end of the year and a half that we spent looking over the NSF budget and what they were invested in, we realized that if the NSF didn’t divest from some of the smaller telescopes, there would be no grants program. The lifeblood of grants and research and science would be gone.

So it was very, very sad to have to recommend a decrease in

funding for Kitt Peak, and it’s really great that this particular project has come along because it gives the NSF a good reason to partner with NASA and to keep the infrastructure on Kitt Peak alive.

Dave Eicher: How significant aside from ground-based research that will be

doing the lion’s share perhaps, as you said, of finding Earth analogs, what will the role be? How significant will the role be for the Webb telescope in exoplanet research? Because there’s a chunk of its time is carved out for this I believe.

Debra Fischer: Absolutely. Well, it’s going to be enormous and completely

complementary. So the Webb will do the things from space that we cannot do from the ground. When we’re on the ground looking through the earth’s atmosphere, in particular it’s very difficult to




see any signatures from the atmospheres of the planets. This is a really weak signal to begin with, and when you’re looking at it through a variable atmosphere that’s tied to your planet, it’s even harder.

So Webb will be great in this regard in terms of looking for

transmission spectroscopy. So as a planet passes in front of its host star and the star lights up the atmosphere of the planet, you’ll get a spectrum, which is actually a combination of the background star and the planet atmosphere, but the great thing about the geometry of this orbit is that the planet then goes behind the star and you’re only seeing the star.

So now you can subtract the star pure and simple off from that first

observation, and what you’re left with is the spectrum of the atmosphere of the planet. So I think we’re going be hearing a lot about that from the Webb research.

Dave Eicher: That’s great. How do you see K2, the new life breathed into

Kepler? Debra Fischer: It’s fantastic. Man. So, I have a project, which I hope some of your

listeners know about. It’s called PlanetHunters.org. It’s a project that Chris Linott taught at Oxford and I put together in 2010 having users around the world look for transiting planets in the Kepler data. We were very sad when Kepler was launched with four reaction wheels and needs three of them to point stably at one part of the sky. It lost one, but it had that redundancy built in.

When it lost the second one there was really a tremendous moment

of sadness. It was May 2013, and people were really worried that maybe this was the end of Kepler. We all knew that we needed two more years of Kepler to be able to find the earths.

We’re not going to get that. We’re not going to get it with Kepler

because the ability to look at that field is gone. We’re not going to get it with K2. So that’s too bad that we lost that incredible science, but what we’re getting in exchange is, I think, really powerful and impressive.

So the engineers realized that there’s a way to save this telescope,

the space telescope, Kepler. If we turn the spacecraft so that the Sun’s radiation is always at the back of the instrument, then we only need two reaction wheels to stabilize it in that plane and look, but we always have to keep the spacecraft with the Sun to its back.




So that means the spacecraft has to drift and it can only look — it’s drifting in the ecliptic plane — it can only look at a particular field for about 80 days and then has to nod on over to the next field, but it’s able to look at regions in the sky like the Pleiades where there’s new star formation, and we can begin to figure out when planets form around stars, what they look like, and it’s just getting incredible returns from supernovae, all sorts of really exciting things.

It will be looking at some point towards the center of the Milky

Way Galaxy, where I think there will be some incredible opportunities.

Dave Eicher: That’s really exciting and the astronomy enthusiasts, of course, are

going to go nuts hearing about things toward the galactic center and also —

Debra Fischer: That’s right. Dave Eicher: — fields like the Pleiades. Of course the original Kepler field was

— what — it was about a 10 by 10 degree patch of sky overlapping Cygnus and Lyra.

Debra Fischer: Exactly. That’s right. Dave Eicher: You imagine that a couple there still — what is it? — 2,900

candidates to look at there, and we really weren’t looking very deeply into the galaxy either. At absolute maximum, I think, a couple thousand light-years for a few examples —

Debra Fischer: Right. That’s right. Dave Eicher: — and yet the bright disk of the galaxy, 100,000 light-years across.

You extrapolate the number out given how small a piece of sky that is and very shallow depth, if you will, of the initial technology we have here. It’s a mind-searing number of planets that you have.

Debra Fischer: It really is. Kepler was looking through almost like a little pencil

beam, which was aimed just above the plane of the Milky Way galaxy and one reason is they didn’t want to look through the disk because there would be so many background stars that would cause field contamination. So this was considered a sweet spot where there would still be a rich field in the original Kepler mission.




But I wish that Kepler could have kept going for two more years and then drifted through the ecliptic plane to give us all of the additional science.

Dave Eicher: Yeah. But there are some other ideas that may not be funded. I

think it’s the European PLATO and some other dedicated telescopes for the future-future.

Debra Fischer: Right. Kepler hands down was game changing. So when we were

using the Doppler technique measuring the wobbles of stars to infer the presence of planets, it was great because from 1999, every year forward, I would be able to say that we detected more planets than the previous year, but we’re still in the hundreds with the Doppler technique; maybe 500 or 600 or 700 planets.

But with Kepler, there was suddenly this incredible watershed of

4,000, 5,000 planet candidates. And the truth is that we have just barely begun to scratch the surface of that amazing database, but even with what we’ve done so far, it’s become clear that almost every star forms with a planet and that the small rocky planets are far more common than the big gas giant planets that we were finding with the Doppler technique. It’s just absolutely revolutionary.

Dave Eicher: So clearly there are trillions of planets out there in the galaxy.

What do you think this says? Are you willing to — I know science is not about speculation — but what is your best gut feeling about the numbers of habitable planets as we define them being liquid water, the right temperature, chemistry that we understand with a good solvent that can …

Debra Fischer: Right. Well, it has to be millions. It has to be millions. So there are

billions of stars. They all have planets, and now we know that planet formation — we have a deeper understanding that at least planet formation is quasi-chaotic. So it’s just a roll of the dice as to what sorts of planets end up landing in the habitable zone. And given that most of the planets are small rocky planets, I mean millions is a conservative estimate I think by any stretch of the imagination.

Dave Eicher: The folks who are very conservative about life in the universe and

about civilizations even, I think, are going to have a harder and harder time as we find more and more planets and they’re Earth-like planets, too because the numbers are — no pun intended — astronomical and then you multiply them by 100 billion as well.




Then the visible universe that we’re seeing may not be the entire universe on top of all of that.

Debra Fischer: That’s right. It’s true … Dave Eicher: So the number is big, but the distance scale is also staggeringly

large when we think of the fun shows on the Science Channel and on Nat Geo of people landing in spacecraft and having lunch with you in Central Park, the distance, it’s an awfully big galaxy, too.

Debra Fischer: I think you just exactly hit the nail on the head. That’s why they

haven’t landed in Central Park is because the distances between planets is so enormous and because in every pocket where life forms on this planet, it evolves to a certain environment. So it’s nontrivial to take that life, whether it’s a battery acid pond or whether it’s this crazy oxygen-rich surface of the Earth. It’s hard to take life from one environment and stick it in another and have it survive.

So I think we’ll be going out into the atmosphere probably not —

it will take a while before we get to the Star Trek Enterprise stage, but I think we will go out relatively soon with small, robotic spacecraft that are essentially nanobot in size. Very tiny because it will be easy to accelerate them to the speed of light.

Then, like your cellphone, as soon as they warm up from the flux of a nearby star, they’ll hone in on that star. They’ll wake up, and they’ll snap pictures and phone home. Send them to a high-gain antenna somewhere in the solar system.

So people are definitely thinking about this, and if the trajectory of

scientific discovery continues as it has for the last decade — and I actually don’t think it will continue like that — I think it will accelerate, then we’ll be hard pressed I think as a species not to want to send out reconnaissance missions and see what else is out there, but that will be different from sending us or our grandchildren out there.

Dave Eicher: Yeah, because that’s really tough when it comes to that much mass

to accelerate you to a velocity that is — it’s a long, long process even with almost no mass.

Debra Fischer: That’s right. Alpha Centauri, the nearest star system 4 light-years

away, maybe you go 10 percent the speed of light, which means that it takes 40 years to get there, but we don’t know how to go 10




percent the speed of light yet. I should just – as a quick disclaimer, but you could imagine that that will happen in the next decades.

Then four years to radio the signal home. So it’s a kind of 50 years

before you get the phone call saying they’re alive or what it looks like.

Dave Eicher: But even without the handshaking, what an incredible thing it

would be to start to get a galactic directory, if you will, near us. It would be really game-changing philosophically and in every other way.

Debra Fischer: It has to happen. I often like to bring up the Sagan cosmic calendar

idea that the Big Bang occurs on January 1 and now 13.7 billion years has gone by, but since we can’t wrap our minds around that number, we now make it one year.

So we scale that to one year and it’s December 31, and the clock is about to tick over. Then you ask when in this time span of one year did the galaxy form? It forms in May. Did the sun form? It forms in August. Did the first life on our planet appear? It appears by September. The dinosaurs are roaming the surface of the Earth on Christmas Eve, and they’re here for a whole week on the cosmic calendar. A whole week.

Now humans in their most ancient forms are here only for seconds.

They appear in the last minute. If you think about technological humans, the part of our species that’s created telescopes and understands radio transmission and has sent spacecraft out, we’ve been here for a millisecond.

If the dinosaurs were here for a cosmic week, we’re here for a

millisecond, but we’ve discovered that the universe started with a Big Bang, that every atom in our body was formed in the core of a star, that there have been species before us that have gone extinct and why they went extinct. We’ve learned all of that in a millisecond. We’ve made the jump from earth to the moon and we’re going to Mars. We have spacecraft on Mars.

In two milliseconds, where will we be? It’s going to be incredible.

If we’re here for a whole cosmic hour, if you just roll the clock forwards, we will be out I think into the galaxy. I think that is definitely our future.




Dave Eicher: Absolutely phenomenal. We have a good, maybe billion years to go until the Sun boils the oceans off the planet and the party’s over.

Debra Fischer: That’s right. Dave Eicher: If we don’t’ get into trouble in other ways – Debra Fischer: That’s right. Dave Eicher: — we’ve got a whole heck of a lot of time as a species to further

investigate things here. Debra Fischer: Absolutely. Dave Eicher: Well that’s incredible. Even if we do find that as we really are

beginning to have the first hints of knowing that planets are everywhere out there, and even if we find that there are habitable planets practically everywhere out there and that there’s life or civilizations abundantly throughout the galaxy and presumably through others, too, that really doesn’t make us a whole lot less special.

The fact that as you elucidated right there, Debra, that we’re made

of star stuff, that the molecule, the atoms in our body were forged in supernovae. The near miraculous scientifically valid nature of life, it’s pretty incredible stuff, even if there’s life out there all over the place and we’re not the center of the universe as we thought 2,000 years ago.

Debra Fischer: That’s right. It just means that the processes that happen naturally

on this planet are happening naturally on other planets. What would be really interesting is to see what the outcome of biological evolution is on other planets.

Dave Eicher: Possibly having a window in some ways to our future as well. Debra Fischer: That’s right. And our origin. There’s so many mysteries

surrounding the origin of life on Earth. Did it get started with an early RNA world. There’s really interesting experiments going on right now in biochemistry that show how RNA actually evolved by a process that most people would think of as natural selection, but here it’s the reaction rate of the chemistry that is the analog of reproductive success in the traditional Darwinian picture of evolution.




So really there’s a driver that pushes prebiotic chemistry toward

life. We’re just beginning to get a sense of that. So I think the discovery of life on other planets is going to tell us a lot about how life got started here and understanding the range of conditions that make planets habitable and the outcome of evolution.

Dave Eicher: Absolutely. We have the only comet, for example, that’s ever been

sampled, return to Earth, had glycine, the simplest amino acid in it. Now that’s a long way from RNA or from making lipids, pre-cells or certainly from DNA, but the stuff of which self-replicating molecules were made was here, we know.

It’s not surprising, of course, every observation that’s ever been

made about chemistry elsewhere, about spectra elsewhere, we know that the same thing is going on everywhere we look, and, of course, why should the universe not be consistent with its physical laws. Of course it should be.

So that’s a lot more ammunition toward saying well, sorry guys,

we’re not unique probably. Debra Fischer: Yeah, but not being the only ones makes it just so much more

interesting, don’t you think? Dave Eicher: Yeah, absolutely. For those who may not know, just briefly Debra,

could you give the listeners a little bit of a tutorial on what are the different methods by which astronomers detect exoplanets?

Debra Fischer: Absolutely. So there are several methods right now. The technique

that I use is called the Doppler technique. If you had an introductory course in physics you’ll remember the Doppler effect, which is we’re looking at the star and as the star comes towards us or goes away from us, the absorption lines that we measure in the atmosphere of the star are blueshifted or redshifted.

So we look at spectra, and it’s a very slow process because we

have to look for at least one full orbit. So that will depend on the characteristic of the planets around the star, but eventually we map out the orbit of the star. It’s sometimes called the wobble technique. And that has I think been one of the most successful ground-based techniques for discovering exoplanets.

Also another ground-based technique is transit observations. We

talked about that in respect to HD 29458, the first star which was




observed to have its planet transit in front of it. This technique just measures the brightness of stars, and since the planet is mostly dark, it blocks out some of the starlight as it’s crossing the disk of the star. And we’ll measure that decrease in brightness.

You can imagine that for that technique the bigger the planet, the

the larger the diminution in light and the easier it is to detect it. So there it was critical to go up into space with the Kepler mission and to be able to measure tinier and tinier dips from smaller and smaller planets.

But there’s also the pulsar timing technique, which was in 1992

used to be able to discover planets orbiting a neutron star. The neutron star is spinning, and it has a light beam that sweeps across the solar system thousands of times per second actually. So it’s like a little lighthouse. And as that neutron star is coming towards us or going away from us, there’s a shift in the frequency of the pulses that we measure and that was used to detect planets around this evolved star.

Also you can imagine looking up and seeing also a sort of wobble,

but instead of having the star coming toward us or going away from us, which we have to measure with spectroscopy, you might imagine that with respect to the background stars your target star is moving around in the plane of the sky. That technique is called astrometry. There haven’t been successful detections of planets with that technique I think mostly because we need to get into space again to have the precision that’s needed.

There’s also a technique which is called microlensing. I think it’s

the coolest technique ever because what’s happening is you’re here on Earth, you’re looking at some bright background star and unbeknownst to you, another little interloping star comes between your line of sight to that background star.

When that happens, that interloper, that interloping star which might have its own planets, bends the space-time continuum and focuses the light from the background star so that you see a sudden brightening. That will happen even if there’s just a star, but if that star also has planets, then there will be secondary or even sometimes third brightenings from the planetary systems that cross what’s called this caustic in space-time. I think I just like that technique because I get to say space-time continuum actually.




Then finally we have to circle around to the one technique that we would all find to be the most gratifying, and that’s direct imaging. You go up. You take a picture of a star, and voila, there’s a planet sitting next to it. So that technique was not possible 20 years ago because the glare of the star just washes out any tiny reflection, pin-like reflection that we could get form the planet itself.

Dave Eicher: And the differences in brightness are unbelievable. Debra Fischer: Yeah, a million. A factor of a million difference in brightness. But

there are new techniques which will actually block out that bright star or use interferometry so that they can see the area around the star and thereby actually detect the tiny, little, faint dot of light from the planets.

So there’s a new instrument that’s being used at the Gemini Telescope in Chile called GPI, and GPI is being used right now to image planets. They’re fairly large planets — Jupiter-sized planets — and they’re at separations that are relatively large, so where Jupiter is in our solar system, Saturn, or even farther away.

So that’s the quick look at the techniques that are available and

being used right now. Dave Eicher: Fantastic. We have a little bit of time left, but I really would like to

ask you about some of your favorite exoplanetary systems as well and to talk a little bit about there are some planets around sun-like stars, there’s some rally oddball systems, too, that are fun to acknowledge and talk about.

Debra Fischer: My gosh. How much time do I have? I’ll start quickly because

there’s so many. Well, Alpha Centauri, I really have a soft spot in my heart for Alpha Centauri –

Dave Eicher: The closest star other than the Sun. Debra Fischer: That’s right. The closest start to the solar system. There are three

stars that are gravitationally bound in that system. From Chile we’ve been looking for the last several years now since 2007. We started looking at Alpha Centauri A and Alpha Centauri B and trying to find planets around them.

The sad news is that because it’s a binary star system, the two stars

are now so close together in their projected separation that we can’t look. We can’t get a good signal anymore until they start




moving apart, but this is the year, 2015, that they begin to slowly drift apart. So in the next year or two we’ll pick up that search again.

So then do I still have time for one more or two more? Dave Eicher: Oh. If you have time, we have a good 10 minutes left. Debra Fischer: Excellent. Becuase my next favorite system is one that we

announced recently. I was a co-author on this paper. It’s a Kepler star, and the star is called Kepler-444, and the star has five planets —

Dave Eicher: Wow. Debra Fischer: — that have been observed to transit. All five planets are inside

where the orbit of Mercury would be — Dave Eicher: Oh my gosh. Debra Fischer: — for our solar system, and they’re all smaller than the Earth. Dave Eicher: Wow. Debra Fischer: They’re roughly half the diameter of the Earth. And that is all cool

stuff, but the most spectacular thing about it is that Kepler-444 the star is more than 11 billion years old.

Dave Eicher: Wow. Debra Fischer: So if we think about what that means, the universe comes into

existence 13.7 billion years ago. The first stars that formed were only made of hydrogen and helium. That’s the only stuff that existed after the Big Bang. Maybe also a little bit of lithium.

It took generations of stars that went supernova that evolved and returned heavy elements that they forged in their cores back into the interstellar medium, and then subsequent stars would form in this more what we call metal-rich environment. Metals for astronomers are anything except hydrogen and helium.

I remember thinking about this in 1999 that there probably

wouldn’t be ancient civilizations because how long would it take before stars had enough heavy elements that the protoplanetary disks around them could form a set of planets.




My money would have been on 4 or 5 billion years ago, which just

happens to be when the Sun formed. Maybe a couple billion years earlier, but I think never would I have imagined that the Sun is 4.5 billion years old and that there could be a star that’s 11.5 billion years old that formed planets.

Dave Eicher: That’s incredible. So the universe, as it always seems to do,

surprises us again with that one. Debra Fischer: Yeah. My surprises always go in one direction in that the universe

is more bountiful in some sense than I ever imagined. This is true just in everything. In everything that I’ve done, I’ve always been surprised that, ah, there’s actually more. There are more planets. They formed sooner than we thought.

So I think that’s an amazing system that really tells us a lot about

how, again, planet formation is incredibly robust, and Alex Wolszczan’s discovery of planets around a pulsar star should have told us that in 1992, but here we are 23 years later still just figuring that out.

Dave Eicher: Absolutely incredible. How about other systems that are favorites

of yours? Debra Fischer: Well, I really love the Upsilon Andromadae system, which was the

first system we found that had three planets around it. I think I like that one for a few reasons. First of all, I joined as a postdoc in 1997 with Geoff Marcy and Paul Butler. Those guys knew that there was one planet in a four-day orbit, and they knew that there was another planet there as well in a long-period orbit.

I would drive from San Francisco, rush up the mountain, top of

Mount Hamilton, and collect data on Upsilon Andromadae trying to squeeze out the last observations as it was fading into the Sun in the early evening so that we could finally get closure on the outer orbit, which looked like it was about two and a half years.

So as I did that, then my job was to, OK, come up with a

mathematical model that describes both the inner planet and the outer planet. It was just a complete failure. A moment of failure on my part that I couldn’t do this. Every model with two planets that I built was wrong. There were huge velocities that were unexplained.




It was only when I included a third planet in my model — so one in between the four-day orbit and the two and a half year orbit — that finally it was a beautiful fit to the data and I could then predict exactly what the velocity of the star would be on the next few nights. I’d go to the observatory, measure it, and it was just so empowering to see this star obeying the mathematical model that I had constructed for it.

So I really love that system. First multi-planet system ever known

outside of our solar system. Again, a hint that if you can form three big gas giant planets inside the orbit of where Mars is in our solar system, there’s something really robust about the process of planet formation, really easy about it.

I love that there was a fourth-grade class from Moscow, Idaho,

who sent me a letter saying, “Dear. Dr. Fischer, we wondered if you had names for these planets because we have some ideas. The inner one, which is only three-quarters the mass of Jupiter should be Ginky because it’s the littlest one in the solar system.” It’s incredible.

“The second one, which is two times the mass of Jupiter should be

Twopiter.” Which I thought was incredibly clever. “Then the outer one which is four times the mass of Jupiter would, of course, be Fourpiter.”

Dave Eicher: Nice. Debra Fischer: So it was good because then I got to go and I presented the results

at a NASA Ames research meeting, and I gave the first talk of the day and I told that cute little story about the fourth graders writing and naming the planets.

Then that was followed by the theorists. I remember Professor

Doug Lin got up and said, “Well, yes, if B — no I mean, C.” Because we were trying to come up with a naming convention for the planets. Finally he threw up his hands and he said, “Look, if Twopiter gets too close to Fourpiter, it’s all over and Ginky will be ejected from the system.”

Dave Eicher: Nice. Debra Fischer: Everybody knew exactly what he was saying. Dave Eicher: Astronomical nomenclature history was made again right there.




Debra Fischer: Exactly. By those fourth graders who were awesome. Dave Eicher: That’s fantastic. Debra Fischer: Yeah. I could go on and on with more of my favorite sort of

children in the annals of exoplanets … Dave Eicher: Would you like to give us one or two more systems? Debra Fischer: So 55 Cancri, which is at least a five-planet system, was one where

I discovered the planet that’s at least very close to what would be called the habitable zone of that star. The planet itself is more massive, Much more massive than the Earth, so it’s more like a Jupiter-type planet or a Saturn-type planet, but we could speculate it might have moons and think about what that sort of a system would look like.

And 47 Ursae Majoris is another one of my favorites. First of all, it

has a Jupiter that’s in a close orbit and then one that’s very, very far away. So it’s mimicking the signpost of our solar system in having a distant Jupiter, but I like that one because there’s actually a Reggae and world music band that picked up 47 UMa for the name of their band.

Dave Eicher: I heard about that. That is really something. Wow. Debra Fischer: So that’s fun, that we’ve been embedded into music culture. I love

that. Dave Eicher: Awesome. Well here’s a really unfair final question then for you if

you would, Debra. Where do you see us, say, 10 years from now with the pace of research that’s going on with exoplanets, five years from now, where do you see things going with exoplanet research?

Debra Fischer: We’re all headed towards trying to find planets like the Earth.

Again, because whatever the chemical drivers were on this planet, they drove prebiotic chemistry to life. So again, this is always, always, always a search for life elsewhere.

There are other great things we learn along the way, but really we’re going to pull out the stops and we’re going to build better instruments and we’re going to observe and detect Earth-like planets around nearby stars so that we can then follow-up with




space missions and look at the atmospheres of those planets and try and see if there’s anything that’s alive there.

So I think it’s going be an incredibly exciting time. Again, it’s a

case where we’re guaranteed a success. We know that those planets are there now. All the stars that we’ve been looking at and not detecting those planets, it’s just because we didn’t have the sensitivity. So as we really double down and improve our instruments, I think that’s what we’re going to get.

The long-range plans of NASA are also geared to follow up on

these kinds of ideas. So NASA will launch the James Webb Space Telescope. They’ll launch a mission called WFIRST, but they’re thinking about the next grand space telescope. The first time I heard about the idea, I thought it was kind of nuts. And then within seconds I realized that we have to do this.

So their grand idea is to take a telescope that’s bigger than Keck —

bigger than the 10-meter telescope at Keck — which is enormous, something like 16 meters across. So a meter is roughly a yard. That’s the diameter of the primary mirror. You’d have to launch it as segmented mirror telescope so that you could pack them all into the spacecraft to send them up. Then send them from the space station to a place between the Earth and Moon, which is called a Lagrange point.

So in our rotating frame where the Earth is going around the Moon

and the whole Earth-Moon system is going around the Sun, the Lagrange point is a point of low potential energy. It’s almost like it feels an equal tug from the Earth and the Moon, so it’s in a nice balance. It doesn’t take a lot of energy to keep it parked in that location. It’s nearby so it’s a serviceable telescope.

So you now send astronauts out and they swap out the mirror

segments every so often. This becomes humanity’s 16-meter telescope in space that will last for 100 years.

Dave Eicher: What a fantastic … Debra Fischer: It’s incredible. The realization that you could actually do

maintenance and upgrades on the instruments and on the telescope itself. So to do something this grand, we’re going have to pull together as a species. It’s going be humanity’s telescope —

Dave Eicher: Multinational effort.




Debra Fischer: — It will be an international effort. My hope is that we’ll have a

strong space program so that we’re part of that vision. Dave Eicher: We certainly should be. This undoubtedly is going to be an

extremely exciting few years to come. We know that you’ll be in the center of it, so we hope that you’ll come back and visit us again and tell us about what’s going on down the road as well.

Debra Fischer: Be my pleasure. Absolutely. Dave Eicher: Well thank you so much for being with us, Debra, today. It has

been an honor, and I’ve really enjoyed it, and it’s been an hour that has been packed with really interesting information.

Debra Fischer: Wonderful. It’s a lot of fun. Dave Eicher: Thanks so much, and thanks to Celestron for sponsoring this.

Debra, we will talk to you soon, and good luck with everything that you’re working on.

Debra Fischer: Thank you.

Superstars of Astronomy Page 1 of 25 Debra Fischer, professor of astronomy at … · 2015-04-07 ·...

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Transcript of Superstars of Astronomy Page 1 of 25 Debra Fischer, professor of astronomy at … · 2015-04-07 ·...