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Discovering New Worlds

A Conversation with John Johnson

What's the focus of your research?

Broadly speaking, we want to find new planets around other stars, which are commonly referred to as exoplanets. We're building up a huge statistical sample. When you have a large number of planets, you can start looking for patterns, trends, and hints about the planet-formation process. The primary goal of my search for planets is to understand planet formation and therefore to understand the origins of the solar system. My characterization work is focused on individual systems of planets or the planets themselves. We're trying to learn about their physical characteristics, such as their radii, masses, average densities, and atmospheric properties. For systems of planets, we're interested in how planets interact gravitationally with one another. The exact nature of those gravitational interactions gives us hints about how planetary orbits evolve after they form. And that probably has a lot to do with how architectures of planetary systems eventually come to be.

What about this field is exciting?

It gets me out of bed every morning. I literally can't wait to see the latest data. It happened to me just yesterday. I was observing remotely in the basement of Cahill until my collaborators relieved me at about 3 a.m., since I had a full workday the next day and needed to sleep. I went to bed at about 3:30, expecting to sleep until 10:30. But I woke up at 7:30 and started thinking, you know, we just observed this new system we found and it's really wacky. It's a hot Jupiter around a type of star that's not supposed to have any hot Jupiters. If this next observation falls on the predicted curve, and it's likely going to be very real, then I'm going to have to think about how to share this with everybody. I couldn't go back to sleep. I was bone-tired, but I was excited and hyped up, so I got up and started working on the paper.

An artist's rendering of a gas-giant exoplanet
An artist's rendering of a gas-giant exoplanet orbiting a so-called subgiant star. Credit: NASA/ESA/G. Bacon (STScl).

I don't know if I would get that level of excitement if I were doing cosmology or if I were studying galaxies—not to say that those fields are not immensely important and have exciting results. I just see new things every day that nobody on Earth has ever seen. It's just really fun being in a field of astronomy that's in its infancy—and being in a place like Caltech where we have Keck access once a month and we can actually watch all this happen.

What got you interested in science in general?

Stephen Hawking. A Brief History of Time—it changed my life. It's kind of clichéd. Half of all physicists are in physics because of that book. That's definitely what got me. Other popular-physics books after that sealed the deal. I was an engineer when I started off as an undergrad, doing aerospace and mechanical engineering. But it wasn't as interesting as discovering things about the universe.

But it all started in college. I can't say that I was one of those kids who begged their dad to buy them a telescope and then used it in their backyards. I had zero interest in astronomy until late in my college career. I was the kid who stayed inside and played with his Legos instead of the kid who went outside and explored under rocks. I was an engineer.

Why should we care about finding exoplanets? They don't plug up oil spills.

Every astronomer goes through that existential crisis. You have to understand that our society as we know it today is shaped largely through a lot of different astrophysical discoveries. The fact that we know Earth orbits the sun came from astronomers 450 years ago. The work that we're doing today is going to impact our culture and our understanding of our place in the universe forever. It's going to happen slowly, but that's what we're in the business of doing. Exoplanets are really good for that because we live on a planet, and we are finding other planets. We're trying to understand the planet we live on—where did it come from? It's the ultimate origin story. We are coming out of the darkness from a couple hundred years ago and we're rubbing our eyes today, realizing that we are on a really small planet around a really average star in an unspectacular part of the galaxy, and we're learning our place in this whole universe. Once we find more planets like our own, it'll further define our place and give us a better universal context for what it means to be human.

Read the full interview in E&S online.

Written by Marcus Woo

Caltech Media Relations