CDS Affiliated Post-Doc Researcher Investigates How to Develop New Methods for Studying Exoplanets

Benjamin Pope, CDS Affiliated Post-doc (courtesy of Benjamin Pope)

Our affiliated post-doc researcher Benjamin Pope, who holds a DPhil in Astrophysics from the University of Oxford, has collaborated with colleagues Joe Callingham and Harish Vedantham at the Dutch national observatory ASTRON on a Nature Astronomy paper investigating how to develop new methods to study exoplanets.

The project had its origins when the Pope and Callingham were discussing the best way to use the newly-released Gaia survey — a huge database of more than a billion stars. Joe had just assisted in developing LoTSS (the LOFAR — Low-Frequency Array — Two-Metre Sky Survey), the most sensitive wide-field radio survey. They set out to look at nearby stars and discern what, if anything, from Gaia shows up in LoTSS. Pope explains that upon conducting a radio survey, nearly everything seen is a galaxy. “People tend to think that astronomy is all about stars but in radio astronomy nearly everything you see is black holes in distant galaxies.” These can be incredibly bright, outshining entire galaxies both in terms of optical and radio energy. Stars like the Sun are much fainter and only a handful of the nearest stars can be seen with radio telescopes — but these two huge new datasets offered a golden opportunity.

In their research, they found that quite a number of nearby red dwarf stars seem to be giving off surprisingly powerful radio waves that have been newly detected by LOFAR. These radio emissions were quite polarized — with circular polarization, like you would pick up with a circular aerial (or cinema 3D glasses). From the radio spectrum, the polarization, the brightness, and the time variation, they discovered that it seemed to much more closely resemble not what the Sun is doing but instead Jupiter, which is one of the brightest objects in the solar system at some radio wavelengths. It is magnetically connected to its volcanic moon Io and this drives powerful currents, aurorae, and radio emission.

One of their goals was to discern what was causing this radio emission. They suspect that a scaled up version of the Jupiter-Io interaction may be the cause. New results from X-ray astronomy seem to back up this conclusion. “This is pretty exciting because if you’ve got this kind of intense radiation being dumped onto a planet by the star. It makes it very hard to imagine this kind of planet being habitable.” Pope makes it clear that the research being conducted is not to search for a Plan B planet for us to move to but rather to better understand if there is life out in the universe.

In terms of the future evolution of this project, this kind of study is just a taste of what will be possible with the Square Kilometre Array (SKA), which is a massive international collaboration between most of the major national astronomy institutes in the world — except for the United States.

As far as data science is concerned, Pope explains that LOFAR was built in the Netherlands, one of the most densely populated areas of the planet. There’s a very careful calibration process needed to filter real astronomical signals from radio stations broadcasting music at the same frequencies, which is a very data-science-heavy approach. When the SKA is built in the remote Murchison desert of Western Australia — bigger than the Netherlands, but with a population of 114 — this noise will drop away we will be able to pick out much more distant stars.

“I think there’s a lot of room for CDS and for data scientists to get involved in this project as the SKA ramps up and the overall project evolves in the next five years. We’re super excited about that,” concludes Pope.

For more information on Pope’s research, please see the research paper references below:

“Coherent radio emission from a quiescent red dwarf indicative of star–planet interaction” is published in Nature Astronomy on February 17, 2020

“No Massive Companion to the Coherent Radio-Emitting M Dwarf GJ 1151” is published in the Astrophysical Journal Letters on February 17, 2020:

Full citation: Pope et al. 2020, ApJL, 890, L19

By Ashley C. McDonald

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