This is the best of our knowledge, a presentation of national productions.
Since the 16th century scientists have speculated about exoplanets, which are quite simply planets
that exist outside of our solar system at orbit other stars in the galaxy.
However, it wasn't until the 1980s that the first confirmed discovery of an exoplanet was document.
There's just billions of these potential planets about there, and we've just discovered a small, small fraction of them.
Today, on the best of our knowledge, our astrobiology series returns, featuring a fascinating conversation with a University of Chicago researcher about exoplanets.
Plus, we'll spend an academic minute finding out how some tiny stowaways in space could cause big problems for future space missions.
I'm Bob Barry, and this is the best of our knowledge.
When most of us were in grade school, we learned about the nine planets that orbit our sun.
Well, we've since lost a planet along the way, but that's not what this is all about.
The point is that there are planets outside of our solar system that are being studied and speculated about.
Here to talk about these exoplanets is Dr. Kevin Stevenson, a post-doctoral researcher in the astronomy and astrophysics departments at the University of Chicago.
He's speaking with the best of our knowledge's science reporter David Castina as part of our astrobiology series on the origins of life about exoplanets.
An extra solar planet, sometimes called an exoplanet, is a body, much like planets we have in our solar system.
You can be all sorts of different sizes. You can have small, earth type planets. We can have large, Jupiter-sized planets.
But all they have in common is that they are outside of our solar system.
So in order to be an exoplanet, you must be orbiting around some other star.
So we have a basic definition, and obviously exciting because as we discover these exoplanets, the potential for life beyond our solar system increases.
I read somewhere in my research here that we have something like the potential when you look at the number of stars and galaxies of 10 billion planets possibly.
In this galaxy and more and other galaxies, absolutely. I mean, there is just billions of these potential planets about there, and we've just discovered a small, small fraction of them.
And obviously we're not going to be able to find all of them, but the nearby ones are, I think, the most important ones from our perspective if we're interested in life on other planets.
Well, obviously the next question is how do you go about this? Now I've heard about the scientists looking at the wobble of the planet in its orbit around a star.
But I see here not only do you have your PhD in physics, and are you on the planetary science track from which you develop a lot of your research out of the University of Central Florida.
But the idea here of time series photometry and numerical methods explain these things.
The time series photometry is actually quite simple idea. You're just taking multiple pictures of the same star over and over and over again.
And when you accumulate those pictures in time, you get an idea of what's happening. So for an example, when we're looking for a planet, we'll take a series of these pictures, and it could be anywhere between hundreds to thousands to tens of thousands of pictures.
And you're looking for changes in the brightness of the system. You can actually isolate the planet from the star itself in the cases that we're talking about here. So we get both light.
Is that because the star's light is so much brighter than anything reflecting off the planet?
It is so much brighter and the planet is so close to the star itself.
So it's the mass of the star overwhelms the planet. So to speak.
Yes. So there's no, there's no, you'll real easy way to differentiate between the two unless you look at the difference in light between the planet in the star as the planet goes in front of the star or goes behind the star.
So from the case when the planet goes in front of the star, we call that a transit event. And then that difference in light can actually tell you a lot about the planet itself.
For example, the radius of the planet, which is then can be used, for example, to determine the bulk composition of the planet, whether it's primarily gas or maybe primarily rock, assuming you know the mass of the planet, which is what you do when you measure the wobble.
So we're talking about a lot of math here, right? So there's a number of complex equations that help you fill in some of these questions that you're trying to answer.
Right, that the calculations themselves have been laid out pretty well. And it all depends on what approximations you want to make the star you could just assume is a circle.
And that's just one simple approximation that's this uniform and brightness. But that doesn't actually work out so well that the star itself tends to be brighter in the center than it is on the limbs. So you take those things into consideration.
You also have to think about atmospheric effects if you're observing from the ground and other sort of systematics that unfortunately can hinder our observations just because the telescope behaves in a certain way. And you really have to try to count for that and some with some sort of equation.
Aha, keyword telescope. Are we talking about the spitzer? We're talking about the spitzer space telescopes in this case. It is actually been a real workout horse in terms of the observations that we could do with exoplanet.
It's been I guess launched in 2003. And originally that we had no idea that we'd be using it for exoplanets. It wasn't designed for this. And it really came about when we wanted to characterize the atmospheres of these planets.
It turns out spitzer is really good at observations in the infrared. Interesting. So infrared light is what we're talking about here and it observes that what was it designed to do originally?
Primarily was designed to look at either objects in the solar system or other galaxies and other planetary disks and obviously being located in space. It can look a lot further than if it were on an earth-based telescope.
Absolutely. There's no way you'd be able to observe at these wavelengths from earth. You have to be in space because the water absorbed in the atmosphere would just completely makes it dark to us.
So you mentioned for to us that there are these pictures sometimes thousands or tens of thousands of pictures of these stars and the light. When you say a picture being theater of the mind right now and radio describe that for us. Is this an infrared picture? What are we seeing? Is it just a dot? Is it anything that we could really make out?
It is like a picture that you would take with your digital camera of stars. Really? And it's not in color, if you will. It is really just a black and white image of the star.
But we can do this at different wavelengths and that does give us our sense of color. And yeah, it is a star and sometimes a star field where you have dozens of stars and you just focus in on the one that you're particularly interested in.
We give us a key, if you will, for understanding what colors might represent, what elements in an atmosphere. He cool. What?
The different wavelengths tell us a lot about the planet itself. When we're looking at planets, what we really want to know is the atmosphere composition and the temperature profile.
So when we look at the planet at different wavelengths, it's like looking at different depths of the atmosphere.
So you could sample high up in the atmosphere or low down in the atmosphere, just depending on what wavelength you're looking at.
And that will give you an idea what the temperature is in that planet and as a function of that height. And it can also gain information about the composition.
So you may be able to tell if there's water, methane, carbon monoxide or carbon dioxide in these atmospheres, just based off these observations that we can do at different wavelengths.
And there are some surprises when you go in and look at that. We'll get to that a little bit later because I want to stick with an exoplanet first and throw out this.
And this is your big discovery, which is UCF-1 decimal point 0.01. Now you can explain why it gets that name. But this is something that I'm sure you're very proud of and has helped you to establish yourself as a scientist.
And why don't you tell us about this exoplanet and how it all came about.
Certainly. I'll start with the name itself. UCF is the name of the university after which it was discovered University of Santa Florida, one being the first system in which we've made the discovery and point 0.01 being the first planet in that system for which we've made the discovery.
Now you tell me something, Dr. Kevin Stevenson, you were a little boy, maybe learning that this science field was something that was for you. Did you ever envision yourself discovering an exoplanet?
You know, I suppose it could almost be a dream to make a contribution like a discovery of an exoplanet. Did I think you would ever happen? No.
No. And you might not even thought about exoplanets even better than possible. But it is quite something to be in this forefront of this research which you can only believe is going to lead to more and more discovery.
The discovery was was serendipitous. We weren't actually looking for this planet. 30 to 50% of all these discoveries in science, they say are by accident or from luck.
So this just proves the point that a lot of lucky coincidences can happen and can lead to these discoveries. So what was the aha moment?
We were looking to characterize GJ436b. This is a Neptune sized planet that we already knew in the system. And we had written a paper in 2010 where we'd come up with some, actually some amazing and interesting conclusions and I can get into that later.
But we wanted to follow up on these observations because to make an amazing discovery, you want to be able to verify these results. And in the data, in these time series data, we started seeing blips that we could not explain.
So this is a decrease in the amount of light and it was occurring at the wrong time. We could not account for it from this other known planet, GJ436b.
So is there some, is there an a man's way to say that that something was in the way or something was blocking the light?
Something was blocking the light. Yes, exactly. And there's no way of knowing whether or not that's a planet because there are a lot of different physical mechanisms for causing this dip in the light.
So you have to go through this rather standard process to eliminate everything else and know whatever is left behind. Well, however, impossible. That's what it is.
So you account for everything that you know and now you're left with something that's an anomaly.
Exactly. And so this, this anomaly as it turns out happened to occur periodically. So we can go back in the data and look in the spitzer archival data and see additional blips that are unexplained.
And is this all called up by computer? Is this all handled almost an instant for you so you can call this up?
It's not handled in an instant, definitely.
So there's some research involved. You do have to do some digging to find out what data is available to you because not everyone is pointing the telescope at the star system doing the same sort of science, but you can get it. You have access to it.
And it's publicly available on the internet. Actually anyone can have access to this data. But it was you.
And you did still to come David Gastina's conversation with Dr. Kevin Stevenson about exoplanets continues. That's next on the best of our knowledge.
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This is the best of our knowledge. I'm Bob Barrett. Our guest today is Dr. Kevin Stevenson, a post doctoral researcher in the astronomy and astrophysics departments at the University of Chicago. He's speaking with the best of our knowledge is science reported David Gastina as part of our astrobiology series on the origins of life. The topic today is exoplanets and Dr. Stevenson continues now with his explanation of how he made a discovery of an exoplanet.
So we were tipped off by these anomalous signals and when we went back to the archival data, we found more of these anomalous signals. We actually determined that it was periodic, which was the biggest thing right there. That I think to me was the aha moment. We said we have an unexplained signal, but it's periodic. So that has got to be something physical. I can't be random.
And from there, we actually predicted a transit. We said, no, we know what the period is. We know when it's going to occur. So let's point the telescope at the system and see if we can catch it in action. And that's one of the most powerful pieces of evidence for believing in this planet is our candidate planet. I guess I should call it is that you can go and predict the occurrence of this event.
But we can't actually see it. You can't actually see it. And we're not likely to see it anytime soon, which makes all of this so fascinating that we have certain tools and certain abilities, but it only goes so far.
And there's a certain amount of faith even involved in this science. So we mentioned before that as you're looking at the composition of an atmosphere and you're looking at the various lights and looking at the color coded key to understand what's what.
That sometimes the answer of what the composition and the atmosphere doesn't always turn out based on what you expect. And I think science obviously goes forward based on previous expectations and measurements and evidence.
But in this case, we're talking about a Neptune sized extracellular planet and the question that came out, which was where is the methane.
Tell us about this because this was another fascinating discovery that has led to some scientists wondering what's going on here.
Absolutely. So this discovery was a precursor to the exoplanet discovery in trying to answer this question we ended up finding the planet. But the question first arose when we were making observations with spitzer, different wavelengths in spitzer are sensitive to different molecules.
So for example, at 3.6 microns, we just so happen to be sensitive to methane and another wavelength we happen to be sensitive to carbon monoxide.
And these two molecules typically don't exist simultaneously in the atmosphere at the temperatures that we're talking about. So this planet here is about 700 Kelvin.
And we would expect to see lots of methane and very little carbon monoxide. This is what equilibrium chemistry tells us. These are what the model tells us. And everyone believes that this is what we should find.
So then we go out and you make an observation and you see no methane whatsoever and tons of carbon monoxide. And you have to ask yourself, why is that?
Why are we seeing all this carbon monoxide when all the models tells that we shouldn't be seeing this.
And what happens then? Because basically I see this funny line, this planet tastes funny. That was one of the articles.
Not that you would be tasting any of these dangerous substances, but it makes the point. So now you've got a dilemma. It doesn't match the model. And now what?
Now you have to come up with new models. It's the way of astronomy. You make some predictions. You go out and observe. And if your observations don't match your predictions, you go back and make new predictions.
So what do you got for us, Dr. Stevenson? What's a new model to this?
Well, there are a couple of different theories. One of them is that you have vertical mixing. So typically we're used to air moving around horizontally on the earth.
But imagine if you had air moving vertically. So from the ground, essentially up towards space. And so you can have this type of air movement in these Neptune-sized planets.
And it's really just dredging up all this carbon monoxide from deeper downwards hotter and carrying it up.
And it upwards. Therefore, the micron distance is explained because it's risen further in the atmosphere.
Yes. Tell everybody what a micron is. A micron is 1 millionth of a meter.
That's a very short distance.
Yes.
Talk a little bit about what you were doing in Florida. And this whole group that's working to look at planets.
You've also mentioned one of your supervisors, Dr. Joseph Harrington, a lot of the literature.
And it's important to mention that this is just one person's effort. This is team effort.
Absolutely. Dr. Joseph Harrington was my advisor there during my PhD. I was there for five years with him.
And not only is it us, but there's a whole group of exoplanet researchers there that really are graduate and undergraduate students for the most part.
And it's really amazing what kind of work they can do. We had two undergraduate students a couple of years ago who published papers as first author papers.
And as an undergraduate student, that's just amazing contribution to be able to make the science.
Absolutely. And of course, you're no slouch yourself getting the order of Pegasus as a graduate student, which is the most I'm reading here now.
The most prestigious and significant student award that can be attained at UCF. You're even on a wall of fame at the University of Central Florida.
Yeah. Actually, it was quite the honor. I wasn't even aware of the program until my final year when I was nominated for it.
And then went through the application process. But it's just such an honor to be put in such a light.
There are student class presidents that are inducted into this and to be recognized for your research is I think a great accomplishment, you know, for the university itself to be recognized from a research perspective as a student.
I just find exhilarating really. Absolutely. And certainly you're taking that experience to the University of Chicago now and your postdoc work and astronomy and astrophysics.
And what are you working on now? What are you doing going forward going forward?
No, I'm no longer using the spitzer space telescope. I've started using ground based telescopes. Oh, and how come you decided to do that?
Well, ground based telescopes offer us a lot more information because we can do what's known as spectroscopic explain that to our listeners.
Okay. So with spitzer data, we're limited to what are known as photometric data, photometric band passes where we look over a broad range of wavelengths, but we only get one simple measurement.
With spectroscopy, we can get multiple wavelengths simultaneously. So we can actually measure the planet at different wavelengths at the same time, rather than relying on one transit for one wavelength, another transit for a different wavelength, and then building up a picture that way because you never know what could be happening in the atmospheres.
If there's variability in the atmosphere, you don't know if that is going to change the results of your photometric data.
So the spectroscopy data really is key because it gives you not only measurements at the same time, but also higher resolution.
So you can actually pick out the specific molecules, whether it's water, methane, carbon monoxide, carbon dioxide, or other hydrocarbons, for example, that we might be able to detect in the future.
And I would imagine this would be valuable too in knowing whether or not something is inhabitable.
Yes, we really are hoping to push the limits in the future of detecting habitability. And that's probably going to be coming up in the next 10 years with the James Webb Space Telescope.
Tell us more.
This telescope is about 6.5 meters in diameter, and it's being launched into space, so it's going to have amazing resolution in the infrared.
When you say 6.5 meters in diameter, you're talking about the lens.
Yeah, the primary mirror is 6.5 meters in the... I mean, I can't even fit in the size of this room.
Absolutely. And the larger the diameter, right, the more powerful the further it can look.
Yes, the larger the collecting area, the more light it can gather, the further away it can look, and the higher precision it can gain in terms of picking out those molecules.
So if you're trying to find, for example, ozone in an Earth-like planet, you're going to need a large telescope in space to in order to pick out those fine details.
Well, obviously, the technology continues to exponentially move forward.
As we continue to go forward, I'm wondering what you think about the answer to the question, are we alone?
I think we will definitely discover... well, we've already discovered a possibly habitable planet.
In terms of verifying that, yes, we will definitely... within my lifetime, we will definitely determine whether or not we have another habitable planet.
Detecting life? I don't know. That's going to be difficult.
There are always signs that say, yes, there could be life on this planet, or life could be hosted on this planet.
But to definitively say, yes, there is life there is challenging. And it's going to take a lot of hard work, but I hope we can get there.
I have confidence that we can do it.
Dr. Kevin Stevenson is a post-doctoral researcher in the Astronomy and Astrophysics Department at the University of Chicago.
He spoke with the best of our knowledge as science reporter David Castina as part of our Astrobiology series on the Origins of Life.
Our coverage is made possible by the NASA Astrobiology Institute through support from the New York Center for Astrobiology located at Rinsleyer Polytechnic Institute in Troy, New York, in partnership with the University of Albany, the University of Arizona, and Syracuse University.
You can learn more about all of the topics in our Astrobiology series at origins.rpi.edu.
No matter what kind of planet may be your destination, if you're an astronaut on a long voyage, some small germs can cause some big problems. That's the topic of today's academic minute.
Welcome to the Academic Minute. I'm Lynn Pascarella, President of Mount Holyoke College.
As an eventual crude mission to Mars becomes increasingly likely, scientists are working to assure astronauts' health during long-term spaceflight.
Leonard Mermell, Professor of Medicine at Brown University, explains why even in zero gravity, an ounce of prevention outweighs a pound of cure.
Mars is no place to develop an infection, so we have to focus on prevention.
Plonghuman spaceflight introduces risks to astronauts in private space tourists because of suppression of the human immune system and microgravity, increased virulence of bacteria in or on their bodies or on environmental surfaces, and confinement in a small, habitable space.
A mission to Mars will take at least 520 days with a 20-minute, one-way communication delay on the red planet. There may be no way to return before the mission is completed.
Pre-flight mitigation strategies include vaccination and screening for several microbial pathogens,
HEPA filtration of the air and prevention of excess humidity, infection control education for astronauts that includes hand hygiene, cough, and sneeze etiquette,
environmental disinfection, and aseptic insertion of devices such as catheters.
In-flight mitigation strategies include point-of-use filters for potable water outlets and catalytic oxidation or pasteurization of potable water.
An astronaut with symptoms suggestive of a respiratory infection should practice cough etiquette and consider wearing a surgical mask.
A waterless hand hygiene product should be used during space travel with design and location of dispensers based on input from human factors engineers.
Termicidal wipes for environmental disinfection should be used. Astronauts should take vitamin D, use a powered toothbrush, and floss teeth daily.
A number of unanswered questions remain. In microgravity, why do humans become immune to suppress and bacteria develop increased virulence?
Is there a substantive change in the human microbiome in microgravity? What are ideal agents that can be safely used for hand hygiene and environmental disinfection during space travel?
Answers to these and other questions may help us mitigate risks in future human missions in deep space and allow us to better understand human and microbial evolution here on Earth.
That was Leonard Memele of Brown University. You can find this, other segments, and more information about the professors on our website, academicminute.org.
Production support for the Academic Minute comes from Newman's own foundation in partnership with Mount Holyoke College.
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Our email address is knowledge at www.wrg. I'm Bob Barrett. Be sure to join us next time for another edition of The Best of Our Knowledge.
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