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Claude
Lafleur, April 26, 2013
| Jared R. Males is an astronomy
Ph.D. student at Steward Observatory, University of Arizona. He is
studying adaptive optics (AO) and extrasolar planets with Professor Laird
Close, in the Center for Astronomical Adaptive Optics (CAAO). He
is the instrument scientist for the VisAO camera, the world's first visible-wavelength
camera for large telescopes.
“The goal of my research, he
says, is to, one day, take a picture of a habitable planet around a star
like our sun - a place where humans could live. We have some work
to do, and some problems to solve, but we will take that picture in my
lifetime.”
Astronomer Jared Males at work.
In April 2013, he published
a paper titled Direct
Imaging in the Habitable Zone and the Problem of Orbital Motion
in which he highlights plans and problems of using AO systems on future
30-meter telescopes to probe the habitable zone of nearby stars.
The main problem his team has identified is that the motion of planets,
while orbiting their star, is not negligible when using large telescopes
over 10-20-hour long-exposure times. “We show that this motion will
limit our achievable signal-to-noise ratio and degrade observational completeness,”
he reports.
Below is the interview he gave
us by phone on April 26, 2013. |
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| Q.: |
How and why did you choose
to become a scientist, and than an astronomer? |
My dad is a scientist, he’s an animal scientist, and my mom is a math teacher,
so I grew up in a house where my dad does lab experiments and wrote papers.
I thus always thought that was all people does. So, I was sort of
set up to think that science is what you do in life.
Somehow alone the way, I start getting into astronomy and physics.
Maybe it’s a sort of a cliché but I saw Carl
Sagan’s Cosmos series and that definitely sent me into the path
that studying stars and the Universe will be pretty interesting.
So, I’d study physics in college, and I really like doing technically challenging
things (software and hardware). So, for me, astronomy is a perfect
combination of that: It’s having to deal with the natural world - you go
out on mountain top, fight with high winds and having to worry about clouds
- but, at the same time, you’re doing this high-tech cutting-edge science.
This is really a nice combination of stuff!
| Q.: |
You are more an engineer
than an astrophysicists, isn’t? |
In some sense, yes. As astronomer, we divided ourselves into sort
of three broad groups of people: there are the theorists, the observers
and the instrument builders. I’m an instrument builder. That’s
really what I do: develop new technologies, take it to the telescope and
make it works.
| Q.: |
How did you become interested
in exoplanets? |
I think the single most compelling question in science is whether or not
life exist elsewhere in the Universe. This is the driving question
for a lot of astrophysicists today and one of the top philosophical question:
are we alone and what it all means if there is someone else in the Universe?
Right now, we’re looking on how it works; life needs a planet which needs
to be about 1 AU from a G-star, so it can have liquid water on it.
I’m not ruling out other ways to have life, but it seems a pretty good
guess that life like we have here on Earth is going to exist on planets
like Earth around stars like our Sun. So, If we’re going to find
life, I think we first need to find planets and characterized them and
understand what they’re like. And it’s why I’m interested in exoplanet.
| Q.: |
And so, your goal, as a
researcher, is to photograph an exoplanet in its habitable zone? |
That’s right.
| Q.: |
Why did you
choose this goal? |
Well, basically, it’s the same logic: we will have to take picture of planets
if we are going to understand whether or not they had life.
Most of the exoplanets we know of today are from radial velocity (RV) and
transit surveys. They gave us fantastic results that tell us that
planets are really common, but the limitation of these techniques is that
they only tell us that a planet is there and they give us a hint of it’s
mass and its radius. So, we’re kind of having an idea of how big
is the planet. But these techniques don’t actually let us take any
measurements of their atmosphere, we can’t understand whether they have
oxygen or nitrogen or water. For this, we’ll have to collect photons
of light from the planet itself and these techniques (RV and transit) are
working with photons of light coming from the stars and watching the effect
of the planet on its star. They are not taking measurements of the
planet itself. With imaging, what we do is we collect photons from
the atmosphere of the planets themselves and try to understand what the
planets are like.
| Q.: |
What are you doing right
now? Where are we in term of photographying exoplanets? |
We already have taken photos of exoplanets. There is the HR 8799
system and beta Pictoris b planets, as well as the Fomalhaut b planet (but
this last one may not be a planet; people are working on this). The
way these planets were found had been using adaptive optics (AO), a technique
for correcting the turbulence in our atmosphere.
As everybody knows, stars twinkle when we look at them. That twinkling
is due to the turbulence in our atmosphere. And that twinkling corrupts
images; no matter how big is your telescope, it limits your resolution
to about 1 arcsecond on the sky. This really limits the things you
could look at (at least, for the bright things). With adaptive optics,
we measure that turbulence in the order of a thousand time a second and
deformed a piece of glasses (called a deformable mirror) a thousand time
a second to correct that turbulence - basically ‘de-twinkling’ the stars.
And so, the kind of instrumentation I’m working on is all AO and my current
project over the last five years – I’m just finishing my Ph.D. at Arizona
- has been working on a new camera for an AO system that works in the visible
range. As of now, on large telescopes, adaptive optics has only work
really well in infrared. But for the first time, we took picture
with AO at wavelengths that we could see with our own eyes. The camera
has done its ‘first light’ six months ago. It’s call VisAO and if
you got to visao.as.arizona.edu,
you’ll see a lot of pictures and information about this system.
Direct imaging that had been done so far are always been on light-separation
of planets that are even further away than Saturn is from the Sun; we’re
talking about orbits of a hundred years. (That is: these planets
take a hundred years to circle around their star.) They are far away
and they are also bright because they are very massive and young (they
are still radiating their heat following their formation). So, they
are bright and far away from their star and they don’t move very much.
It only takes an hour to photograph them, and they don’t move.
In our study, we realized there will be a problem for our current-generation
VisAO camera if we tried to do this around, for example, Alpha Centauri
A. The problem is that we need long-time exposure – 10 to 20
hours – if we were to detect a planet. And because we will search
for planets in the habitable zone, with orbit of roughly one year, the
projected orbital motion is high enough that it smears out on our detector.
On our photos, they won’t look anymore like planets but more like smear
blobs. That makes them hard to identify and hard to detect.
We also realized that this will be a general problem when you scale it
up with the next-generation of giant telescopes. And since we expect
that AO camera will be one of the premier science instrument for these
telescopes, we realized that we need to think this thorough and understand
how this phenomena is going to affect these giant telescopes.
| Q.: |
And what could we do to
tackle this problem? |
There is two ways to look at it. One on which we had spend a lot
of time in analyzing: if we look at a star and we have no idea whether
there is a planet or not – what we call a blind search -, we can look at
our images and find hints if there is a planet there and then, post-processing
with software the orbit in those images. So, we could take a bunch
of shorter exposures and digitally moving them around along possible orbit
of these planets and see if we can make the planet pop out of the noise
by doing that.
But the more likely way to solve the problem is to use other techniques
- radial velocity or transit or most likely astrometry - to tell you that
there is already a planet, so we’ll have some idea what the orbit of the
planet we’re looking for is on. You thus use this information to
chew your analysis, which makes your problem a lot easier. So, while
you’re doing your 10-to-20-hour exposure, you know where the planet is
during each step of that exposure.
But it’s still messy because in science, we always have error bars [error
margins] - there are always uncertainties - and so you have to take them
into account. In other words, you’ll never know the orbit of the
planet perfectly. So, it’s still messy but it is solvable, it is
something that we can deal with and start finding some planets.
| Q.: |
Are we talking about a new
method to find planets or simply a method to study planets that we already
know? |
I think the problem of signal-to-noise ratio of the planet moving around
its star will limit our ability to do large surveys. But I’m guessing,
since there could be other solutions other than the ones we’d considered
and I think that people will really thought a lot about it and find a way
to figure out how to solve this problem. But I think most likely
the way 30-meter giant telescopes are gonna work, they’re going to be looking
at stars where we already know there is a planet. I think we’re gonna
find that it will be the most efficient way to do these long-exposures.
It’s probably not a way to find new exoplanets with giant telescopes, but
it’s a way to characterize those planets we know that are there.
| Q.: |
Why not just look around
a star just to see if there is a planet or not? |
Well, in general, we do that with adaptive optics in direct imaging and
such surveys are planned in space using space-based chronographs.
It’s a good way to find planets, especially since radial velocity and transit
methods can only find planets that are align with our line of sight.
So, direct imaging has been finding planets. The system HR 8799 is
in fact a system of planets that is nearly face on, so RV would never had
found these planets. So, it will have a place as a way to find planets.
But, as we’re moving in this regime of habitable zone and into fainter
moving planets close to their star, we expect to have this issue of really
long-exposure times and using very specialized instruments. My guess
is that it’s not going to be a very efficient way to find new planets because
it is very, very hard to spatially resolved the light from planets since,
as yon know, a planet like Earth is over a billion time fainter than a
star like the Sun. And that’s a really, really hard technical challenge!
| Q.: |
What could we expect to
see on these long-exposure photos? Could we hope to distinguish some
planet’s features? |
Yes, but probably not in the way you’re thinking! We won’t have pictures
of clouds or oceans. In other words, we won’t see spatially-resolved
features: we won’t see a hurricane on the surface of a planet. What
we will do is to photometrically observe these planets, we will take measurements
of the spectrum (their spectra) at various point and using that to diagnose
things like water clouds and oceans, or whether or not there is oxygen.
There are many different things we called biomarkers and that you could
look for and that are hints that there is some chemical process on that
planet. That’s what we will do.
| Q.: |
On these pictures, we will
only see a blob of light? |
Yes. And with a spectrometer, we will see what’s going on in the
atmosphere of that planet.
| Q.: |
When could we expect to
see some results with the kind of camera you’re working on and placed on
a giant telescope? |
For these giant telescopes. I think it is roughly a decade from now. That’s
a round number; it could be 8 or it could be 12 years.
But right now, we’re building our instrument and putting them to telescope,
we sort of laying the ground work for the new telescopes. And we
are already achieving some results. For example, there is the large
binocular telescope here at Arizona that is constantly producing results.
And so, while we are getting ready for these giant telescopes, our current
generation of 8-meter telescopes are doing great work.
And I’ve just received a NASA’s Sagan
Fellowship which mean that, during the next two years, I will be working
for NASA, just continuing this work, continuing our effort to push our
instrumentation to the point where we could start taking pictures or stars
with planets around them. It’s pretty exciting to keep working on
this!
| Q.: |
And we will follow your
works! Thanks Jared. |
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