The researchers ready for the James Webb Space Telescope

Part I: An interview with Taylor Bell

In this two-part series we’ll meet two researchers who will soon be working with data from the recently launched James Webb Space Telescope. In this episode, Part I, I speak with early career astronomer Taylor Bell about his work categorizing exoplanets and the path that led him to where he is today.

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This transcript has been lightly edited for clarity.

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BAERI: This is For the Love of Science, a podcast from the Bay Area Environmental Research Institute. I’m Erin Bregman. In this show, we hear directly from the institute’s scientists, engineers and mission specialists about the groundbreaking research they’re doing right now in Earth, environmental, and space sciences, and learn about what their work can teach us about our Earth and our universe.

Welcome to our next two part series. In these interviews we’ll meet two researchers who will be working with data from the recently launched James Webb Space Telescope. In this episode, Part one, I speak with early career astronomer Taylor Bell about his work categorizing exoplanets and the path that led him to where he is today. In part two, we’ll learn about some of the leaps in infrared astronomy over the last 50 years and how astrochemistry research could lead us to an understanding of the origins of life on Earth. That’s all coming in part two. But first, here’s Taylor Bell.

TAYLOR BELL: I’m Taylor Bell, I’m a research scientist at the Bay Area Environmental Research Institute, and I’m working with Tom Greene at NASA’s Ames, studying the atmospheres of extrasolar planets, planets orbiting stars other than the sun. We study things like the chemistry of the planets. What are they made of? How do they form? And things like the dynamics of the planets’ atmospheres. So, how hot is the day side, how cold is the night side? What are wind patterns on the planets like? And we can’t do this in a way that we might think of for the solar system. We can’t individually see these planets and their surfaces and their clouds. We see them just as changing brightness. And so to understand them, we have to get pretty inventive compared to what we would be able to do in the solar system.

Taylor Bell

BAERI: How did you get started doing all of this and why did you go down this path in particular?

TAYLOR: So in grade nine, I thought I was going to be an architect or something. I didn’t really know what, but I thought I liked architecture. And then in my grade nine physics class there was a space unit and I thought, ‘Oh wow, that’s really cool, I’d like to do… something.’ But I didn’t really understand much of anything at that point. And I thought, ‘Oh, I’ll study black holes or quantum physics or something.’ I didn’t really know. But in the second year of my undergrad in physics, I got to take my first observational astronomy course where you use a little telescope on the roof of the physics building, and you look at a star and you try and learn things about it. And I thought, ‘Okay, yeah. That’s what’s really fun, is studying these things with telescopes.’ And as a kind of side project to that course, we got to do some amateur astronomy things where we would look at transits of exoplanets using these small telescopes, and we could contribute it to this public database of transits, and trying to look at changes in the timing of transits that might tell you that there’s another planet in that system that’s undiscovered. Getting to do that as a second year undergrad was like, ‘Wow, this is super, super cool.’

BAERI: Where was this? Where were you in undergrad?

TAYLOR: Yeah, I did my undergrad in my home city of Saskatoon, Saskatchewan, in Canada. It’s not a place that’s known for its astronomy. But I had a mentor there, Stan Shattuck, who was everything that you could ask for in a mentor. He was really encouraging and encouraged us to do these side projects for fun and grow our data analysis skills and encouraged us to do these summer research projects at different universities around the country. And thanks to him, I am where I am now.

When I introduce myself as an astronomer or something like that, people are always like, ‘Wow, you must be so smart. You must be a genius.’ And to me that’s one of the saddest things because to me that means that that person can’t even imagine themselves as an astronomer. And astronomy is not a field of geniuses by any stretch of the imagination. We’re human beings. We’re all a big community of people, all working towards the common goal of understanding the whole broad field of science. And we’re all making contributions. And especially observational astronomy is not a very math heavy region. That’s the second most common thing I hear is like, ‘Oh, I hated math in school.’ It’s like, well, astronomy doesn’t really use — I mean, it really depends on your subfield. For exoplanet observation or characterization, there’s not a lot of math that is done. There’s certainly math that you can do, but it’s really a data analysis, software development, day to day job. There’s many different people that can be an astronomer. And if people wanted to, there are ways that they can contribute.

BAERI: What specifically are you looking at and trying to learn with the projects you’re on?

TAYLOR: The main things are kind of the theme of chemistry and the theme of atmospheric dynamics. So in the theme of chemistry, there’s just broad questions of: What is this planet made out of? Does it have water, does it have methane, does it have carbon monoxide or carbon dioxide? With that, you can also start asking questions of: Are there clouds in the atmosphere? What might those clouds be made of? And these types of questions are kind of vague and you might wonder, why do you really care what an exoplanet is made out of? But it can help tell you things about how the planet formed. If there’s lots of carbon in the planet compared to oxygen, that might tell you where the planet formed with respect to its star. Was it formed really far out where Pluto is now and then it moved into the middle of its solar system? Or was it formed close where it was hot and there was more of one type of molecule than another? And you can also start to ask questions of: Are there signs of life or the potential for life on planets?

The next general theme is atmospheric dynamics. So, studying with transit observations where we’re learning more about the night side of the planet where the planet is coldest. For eclipse observations, we’re learning more about the dayside. And then there’s also phase curve observations where you observe a planet throughout its entire orbit and you see the kind of continual modulation in brightness as you go from seeing the hot dayside to the cold night side and back. And with that you can learn about the entire surface of the planet at some very coarse resolution and learn about what are the winds like on the planet? How is heat getting moved from the dayside to the night side? Those are the main themes that we’re trying to study.

The oncoming age of James Webb definitely helped shape what I wanted to do. I considered different fields in exoplanet science. There’s many different ways you can characterize things. There’s the Hubble and Spitzer kind of technique. There’s more ground based techniques. But knowing that Hubble was up in space, James Webb was going to be coming, it definitely helped shape what I was wanting to do.

I was definitely prepared for the possibility that something would go wrong with James Webb or that it would be pushed back more years. It’s happened throughout my career, and so I’ve been diversifying my research skills. I’ve used many different techniques. I’ve used Hubble, I’ve used ground based telescopes and different types of ground based telescopes. It’s definitely going to unlock a different type of research question that you can ask with JWST, but JWST is not so much a telescope, it’s an entire observatory. It has all these different things that it can do for so many different fields of science. Even just in exoplanets, there’s the intention to use all four of the instruments in different ways, especially in the first year or two, to understand what instruments work best. Maybe in two years time we’ll learn, ‘Oh, this instrument, it’s just not the best way forward. Sure, it works just fine, but if you use this other instrument, you get twice the amount of data for basically the same amount of time.’ Especially at this early stage, we’re all just trying to learn. We’re trying to find what works best for our particular system.

BAERI: You must have been relieved that it got into space and opened.

TAYLOR: Yeah, yeah. That was a wonderful Christmas present. Seeing it launch successfully on Christmas morning, it was something like 4 or 5 a.m. Christmas morning. It was a brutal thing to wake up and see, but very, very exciting, and then I could go back to sleep safely knowing that it’s on its way, the experts are in control, and it’s going to work out.

BAERI: Can you tell me what planet spectroscopy is and why it’s useful?

TAYLOR: So different atoms and molecules will have different wavelengths at which they absorb or emit light. And so by looking at different wavelengths, you can learn about different molecules in planets’ atmospheres. So you might look for water or you might look for carbon dioxide, or you might look for methane, which is something that people think might tell you that, potentially, there could be life if there’s a lot of oxygen in the atmosphere as well.

And another thing that you can do with spectroscopy is look at dynamics of the planet’s atmosphere. Because different wavelengths get absorbed by different molecules, and the abundance of molecules changes with altitude in the planet’s atmosphere, at higher altitudes, it might be colder or hotter, and so different molecules might be preferred there. And so at different wavelengths you probe different depths into the atmosphere or different altitudes from the surface. And so you can study how hot it is at this altitude versus that altitude. And that can tell you different things about how heat is moved around on the planet vertically or horizontally. So spectroscopy really unlocks a lot more information.

Most of the work of characterizing these things has previously been done by the Hubble Space Telescope or the Spitzer Space Telescope, both of which had very narrow wavelength ranges. Spitzer was more of the imaging style of a telescope. And so you got to know between these big chunks of wavelengths, what is the planet’s size or what is the planet’s temperature? But you didn’t get to know like a thousand little wavelength elements in that big chunk how it varied.

And so we have some vague pictures, but until we start getting these full wavelength spectra of the planets all at once, we don’t really know how much we should trust our results. And so, James Webb will really kind of solidify a lot of the understanding from what we got from Hubble and Spitzer. And maybe we’ll learn that Hubble was actually doing a great job and we know we can trust Hubble, and that will be great because then we have two telescopes at the same time that can do fantastic science. Or maybe we learn, okay, we can learn this general take away from James Webb, but reapply that to Hubble observations. And Spitzer is decommissioned now, but we can then take the lessons learned from James Webb and learn whether Spitzer was leading us astray or if we were just leading ourselves astray with good data. James Webb also has a much broader wavelength range than Hubble and covers much in much higher resolution than Spitzer. Where Hubble mostly looked for water, James Webb is going to be looking for so many different molecules all at once. And so we’ll get a much more holistic image of what the planet might be made of.

BAERI: What does that data look like when it comes in, and how do you take that data and actually understand something new from it?

TAYLOR: So it starts off as individual pixels on James Webb. James Webb behaves a little differently than your typical camera. Instead of having a shutter, it kind of continuously reads. And so you get like the change in a pixel’s brightness over time. And then James Webb is really far away from Earth, and so it has to transmit that data to Earth. And so it uses the Deep Space Network, which is a collection of three different observatories around the Earth. There’s one in California, one in Spain and one in Australia. And so the Earth continuously has contact with James Webb. So James Webb downloads that data to the Earth. The Space Telescope Science Institute in Baltimore, Maryland, then does some initial checks on the data, just to make sure nothing went seriously wrong, and then they’ll do some initial calibration steps at differing levels. And then they put that up on their website and give to the people who requested those observations a password and you can go and download the files.

For exoplanet astronomy, we typically don’t use the calibrations that they did because they’re more suited to galaxy observations. And so we start back from scratch and we have a data analysis pipeline that goes from individual pixels to changes in brightness over time. So that typically means you take a box on the image and you say: Here is where the star is, just tell me what the sum of the brightness is in that box. And you do that several thousand times. Instead of images, you get kind of a plot where you get brightness over time, and we call that a light curve. And then you have to fit that light curve. You have to say: The detector is introducing these artifacts and so fit some squiggles to the data, and the planet passed in front of the star, so fit a transit model. And you fit all of those simultaneously and you try and reproduce the observations with a model. And then that tells you something about the transit depth at this wavelength, and the orbital period and the time of transit, things like that.

And then you go from, ‘What is the transit depth?’ to, ‘What does that mean for the atmosphere? How do you understand the composition?’ Some other people will perform a retrieval. So they’ll take a chemical model, and say: If I increase the amount of carbon or if I increase the amount of water, what does that do to the spectrum? And they’ll do this in a fitting routine and say, ‘Okay, it looks like we can constrain the water abundance to this, the carbon dioxide abundance to this.’ And then you kind of publish that collection of: The transit depth was this that probably means that the atmosphere is made up of this, and this is what we think that implies for the formation of the planet.

BAERI: How many different people does it take working on something like this to understand what a planet’s doing? It sounds like everyone kind of has their little part.

TAYLOR: Yeah, it’s a very collaborative field. For the kind of data analysis pipeline that I have been developing, there’s about 12 of us that are just writing the data analysis pipeline. And then the hope is that the data analysis will hopefully not be too hard after this is written. We’ll see when we get real data, you never know what’s going to happen. But the hope is that one or two people will analyze the data and fit it and say ‘The transit depth is this.’ And then you’ll pass it on to another person and they’ll do the retrieval step. And then you’ll have several other people that look at all of the different steps that you did and say, ‘I don’t think this part makes sense and that’s giving you wrong results here. Can you try this different tweak?’ And so you run it all again and you see what the result is. Yeah. Then you might get other people on the team to say, ‘Okay, does your retrieved abundance make sense from a general circulation model?’ And so you have someone who will model the entire atmosphere of a planet in a much more complex way and say, ‘That mostly makes sense,’ or, ‘We don’t understand why that doesn’t make sense, but here’s the way it doesn’t make sense, and this is an avenue for future research.’

The typical research paper with these types of observations, it often has at least ten people that have contributed in many different ways, even from just writing the proposal stage, that is a significant effort. And so those people get recognized in the paper as well. Every paper is just an incremental step. You’re basically never overhauling the entire field. You’re just saying this is what this seems to suggest, and people will disagree or agree, and over time, you’ll work towards a better understanding.

BAERI: Thank you to Taylor Bell. Our music is by Danny Clay. You can learn more about Taylor and his work by visiting www.taylorbell.ca. That’s it for this episode. See you next time.