Spotlight on research:DCU researcher discovers weather patterns on distant exoplanet

This week's research spotlight is on Dr Ernst de Mooij, Lecturer in DCU School of Physical Sciences

You study planets that orbit stars outside our own solar system. How do you look at them?

“We know that there are billions of stars in our galaxy and until just over two decades ago, we didn’t know if there are planets around other stars. Over the past two decades we have found thousands of planets around other stars. We call these exoplanets, but they are not that easy to see. We can measure the mass of a planet based on its wobble and we can only measure the size of the planet if the orbit is aligned in such a way that the planet passes between its star and the Earth. If this is the case, then the planet blocks some of the light reaching us from the star, and by measuring this dip we can directly measure the size of the planet. We can also use the wobble and the frequency of the dips in light to work out how often the exoplanet goes around its star.”

What are you looking at in particular?

“I tend to work on exoplanets after they have been found, and I am interested in studying their atmospheres, if there is weather on these planets.”

How do you find out about that? “I use data from the Kepler spacecraft, which is out in space looking for exoplanets, and I use observations from telescopes on Earth, mainly telescopes in Hawaii, Chile and La Palma. One of the difficulties though of using ground-based telescopes is that you need to correct for the effects of the Earth’s atmosphere, which can distort the signals coming from space.”

What have you shown about exoplanet weather?

“We have been able to detect evidence for weather on HAT-P-7b, a giant gas exoplanet almost twice the mass of Jupiter that orbits a star more then a thousand light years away. Working with colleagues in the University of Warwick and the University of London and Queen’s University Belfast, we used the data from Kepler that had been recorded for this planet over four years, and we divided the data into smaller chunks so we were able to search for variability over short timeframes.

What we found was that the brightest point on the planet moved between its morning side, where clouds from the night-side would dominate, to the afternoon side, where the thermal hot-spot dominates.

These variations could be due to clouds that form on the night-side of the planet and evaporating on the much hotter morning-side. Due to changes in wind speed etc., there could be more or fewer clouds on the morning side, resulting in the observed variation.

This is the first direct evidence for weather on an exoplanet.”

How did you become interested in exoplanets?

“When I was a kid I wanted to become an astronaut but I went into astronomy instead! I studied at the University of Leiden and did a PhD there on exoplanet atmospheres. Since then I have been working in that area as a post-doctoral researcher in Toronto for three years and then in Queen’s, and I moved to DCU in October last year.”

What are you working on now?

“I am working on several other exoplanets, including one that we think might have large rings, much like Saturn does. Based on its orbit we expect to be able to detect any rings as it passes almost exactly between the Earth and its star later this year, and I am working on ways to optimise that detection.”

Do you think we might find life on other planets?

“We currently base our expectation on what signatures we might see from life on the one example we have, the Earth. This means that we may fail to recognise life if it is very different from what we expect.

The question whether there is life elsewhere in the universe, and by that I mean simple life (such as bacteria) is one of the key questions that we would like to answer. Trying to answer this question is one of the motivations for me to continue my study of exoplanet atmospheres and to develop new techniques that, with the next generations of telescopes, can answer that question.”