Northern lights, stellar winds and exoplanets. This is what turned the astronomer’s doctoral research. PhD candidate astronomer Rob Kavanagh developed mathematical models to better understand the interactions between exoplanets and stellar winds and to define the characteristics of exoplanets. He will receive his doctorate on November 15.
Just like the northern lights
Exoplanets are planets that orbit stars other than the sun. They are sometimes difficult to detect, but now it appears that interactions between exoplanets and stellar winds produce signals that radio telescopes can detect. Stellar winds are hot streams of charged particles that continually escape from the surfaces of stars like the Sun. “When stellar winds collide with the magnetic fields of orbiting planets, the interaction can produce bright emission. On Earth, we can see emissions like the aurora borealis.
Modeling stellar winds
Last year, signs of these interactions were detected for the first time in other star systems with the Low-Frequency Array (LOFAR) radio telescope. About twenty dwarf stars that emit radio emissions have been found. This could be due to exoplanets orbiting these stars, although they are not currently known to host any planets,” says Kavanagh. In mathematical models, he simulates stellar wind environments. In this way, Kavanagh hopes to understand better the signals that are generated by the interaction between exoplanets and stellar winds. “Kavanagh’s research also helps to interpret the new LOFAR observations,” says his supervisor Aline Vidotto of the Leiden Observatory.
Rob Kavanagh
Exploring exoplanets
Kavanagh’s models are not only useful for detecting new exoplanets. The radio emission also provides all kinds of information about, for example, the size of the planet and its orbit around its parent star. Kavanagh: “Looking at the planets in our own solar system, we expect large planets, orbiting close to their parent star, to produce the strongest radio signals.
Is there life on an exoplanet?
In addition, the strength of the emission can also reveal something about the properties of the stellar winds themselves and the size of the magnetic field around an exoplanet. “Important information, because Earth’s magnetic field is likely to have ensured that we now have an atmosphere.” Therefore, the presence and size of a magnetic field provides astronomers with an indication of the habitability of a planet. “And that’s useful in the search for extraterrestrial life.”
To ASTRON
Kavanagh is now working as a postdoctoral fellow at ASTRON, the Netherlands Institute for Radio Astronomy. “I’m going to continue developing models here and I’m also going to start looking at brown dwarf stars. These stars emit an enormous amount of radio emission, which is puzzling. The more I think about it, the weirder I find it,” laughs Kavanagh.
In the meantime, Vidotto is happy that Kavanagh is staying in the Netherlands, looking forward to future collaborations. “We started our research together in Ireland, but halfway through Kavanagh’s PhD, I moved to Leiden to facilitate collaboration with my astronomer colleagues,” says Vidotto. After some hesitation, Kavanagh joined his supervisor. “It was a big challenge to migrate suddenly in the middle of a pandemic, but I’m glad I did it.”
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