Jason Steffen - Five way interview

Jason Steffen is associate professor of physics at the University of Nevada, Las Vegas. A longtime science team member of NASA’s Kepler mission, he has contributed to the discovery and characterisation of thousands of planets that orbit distant stars. His new book is Hidden in the Heavens.

Why astronomy?

I originally wanted to be an aerospace engineer to design and build airplanes.  My undergraduate institution didn't have aerospace engineering:  I took an astronomy class my first quarter, and decided to major in physics.  My degrees are in physics rather than astronomy, but my research is all on topics related to astronomy in one way or another. 

For a period of time after graduate school I did experimental physics research on dark matter and dark energy.  I was working at a national laboratory, a big atom smasher outside of Chicago, called Fermilab.  At the same time that I was doing this work for Fermilab, I also worked for NASA on the Kepler mission to find exoplanets.  Half my salary came from one project, the other half from the other.  It was pretty intense, but I learned a lot.  Eventually, I decided that I needed to stick with one research area and chose to stick with exoplanets. 

Why this book?

For a long time I've been interested in writing a book.  I enjoy explaining the things that we've collectively learned and how we learned them.  It had been just over a decade since the original Kepler mission launched, so it was far enough in the past that we could give a decent assessment of what its significance was, but not so far in the past that everyone was retired or dead.  So, I still had access to my colleagues, as well as a copy of all of the emails that were shared among our working group.  It seemed that the time was right to tell the story of the mission.

We’ve now discovered thousands of exoplanets - are we still finding anything new and unexpected?

A lot of exoplanet science has moved on from discovering new systems (although that still happens).  Today, our advances often happen in characterizing the properties of those planets.  Measuring their masses, the composition of their atmospheres, the nature of the planetary system that they live within, the properties of the star that they orbit, etc.  We are learning a lot about how the sizes of different planets in a given system, and their orbits, relate to each other and what that implies for their histories, and the history of the solar system.

We also have instruments, like the James Webb Space Telescope, where we can see the different chemicals that are in the atmospheres of these planets.  That tells us about the conditions where they formed, and whether or not their surfaces might be conducive for life to exist.  Each day there are a dozen or so new papers that share new results, so there is still consistent progress in a number of areas.

What’s next?

 In exoplanets, there is ongoing work with the TESS mission (Transiting Exoplanet Survey Satellite).  That is discovering new systems on a regular basis.  There are also plans to launch the PLATO mission, which is a successor to Kepler, this time led by the European Space Agency.  Another satellite, the Nancy Grace Roman Telescope, led by NASA will be able to detect a lot of planets across our galaxy that we currently don't have the capability to see.  So, the field of exoplanets is not slowing down any time soon.

What’s exciting you at the moment?

My current research is looking at the chemical composition of the planets themselves, not their atmospheres, but their interiors.  Planets form in a disk of material that orbits the newborn star.  As that disk cools, different minerals condense and rain down to the disk midplane where they ultimately form the building blocks of planets.  My group models the condensation of those different minerals so that we can predict what the planets will be made of.

My group also developed computer software that models the internal structure of planets given their composition.  So, we can take the output of our predictions for the composition of the planets, and then turn it into real planets using this other software.  (We called the software MAGRATHEA, after the planet in the Hitchhiker's Guide to the Galaxy where planets are made to order.)  Ultimately, we are trying to predict the details of what exoplanets are like, and the conditions under which they formed.

Photograph (c) Robert Royer III

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Interview by Brian Clegg - See all Brian's online articles or subscribe to a weekly email free here