Why do you study exoplanets?

We live in a fascinating era in terms of astronomical knowledge. We now know with certainty that many other stars besides our own Sun have planets orbiting them. Many scientists and engineers are working to advance our understanding of these exoplanets. The implications of such exoplanetary research will affect many aspects of humanity’s understanding of the universe, including the possibility of life existing elsewhere. To learn more about the study of exoplanets, we spoke to Yoni Brande, a PhD student at the University of Kansas who studies exoplanet detection and characterization.

What are you doing with regards to exoplanet detection and characterization?

Before I started my PhD at Kansas, I worked at NASA Goddard, where some of my advisors were astrophysicists working on the newly launched Transiting Exoplanet Survey Satellite (TESS) mission. I spent about half my time working with them on transiting planet discovery, learning how to process the data and how to model planet transit light curves. I also worked on simulating the feasibility of using the upcoming James Webb Space Telescope (JWST) to directly image planets around some of the nearest stars. These were great introductions to planet discovery efforts. As I got ready to leave NASA and move to Kansas, I started working more on transiting planet characterization, studying these planets’ atmospheres with transmission spectroscopy.

With my PhD advisor, Ian Crossfield, I’ve been working on using the Hubble Space Telescope to do transmission spectroscopy of exoplanets. He has a large Hubble program to investigate the atmospheres of Neptune-sized planets. We’re primarily interested in looking for things like water vapor or methane in atmospheres, but we’re lucky if we see anything at all! These planets are warm, and they often have high-altitude clouds or hazes that block our view of any recognizable gases at the low spectral resolution that Hubble gives us. Hopefully, we’ll soon be able to use more sensitive and precise observatories like JWST to find out what these planets are made of.

Why are you interested in studying exoplanets?

We’ve been exploring the Solar System for over half a century now, and we’ve been studying exoplanets from afar for the last two and half decades. Despite this, we still have huge gaps in our understanding of planets both in our Solar System and beyond.

Our models for the formation of the Solar System explain our local observations fairly well. However, we’ve discovered over 4,000 exoplanets and none of them exist in systems that look much like our own Solar System. There’s certainly observational bias since we’re most sensitive to systems unlike our own – systems that have large planets orbiting very close to their stars. However, there’s always the chance that the Solar System is actually rare! This could have significant implications for the search for extraterrestrial life. If life can only develop in Solar System analogs, and if those systems are rare, then life might also be rare.

This is why the liquid-water habitable zone is an appealing area of study, since we think planets that can support liquid water on their surfaces should be relatively common. Some estimates say half of all Sun-like stars should have rocky planets capable of supporting liquid water on their surfaces. In order to know if this is actually the case, we need data on lots of planets, which makes our current and future observational capabilities really important.

What is a common misunderstanding about exoplanets?

When I give public talks, people often ask whether artists’ conceptions of exoplanets are actual images, or if they are representative of what actual images would look like. I think people often confuse our capabilities to observe certain aspects of exoplanets with the ability to take a visual picture, like you might take of the Moon or Jupiter. Exoplanets are all so far away that we often don’t see anything directly from the planet! Even in the few cases where we can see light coming directly from a planet, there’s no spatial resolution: The planet looks like a single point of light. So, the artists’ conceptions are just hypothetical images of what exoplanets might look like. They’re meant to guide the mind to a more familiar image, compared to less obvious astronomical data.