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Researchers simulate the formation of lightning on an exoplanet for the first time.
Lightning is well known on Earth and also occurs elsewhere in our solar system. But could lightning also exist on planets orbiting stars very different from our own?
Researchers from TU Dortmund and their partners have moved a step closer to answering this question. For the first time, they used computer models to simulate how the initial stages of lightning might develop in an exoplanet's atmosphere.
Using data from the James Webb Space Telescope, they studied K2-18b, an exoplanet located approximately 124 light-years from Earth. An exoplanet is defined as a planet that orbits a star other than the Sun.
"Of course, we cannot see lightning on a planet 124 light-years away. However, observations from the James Webb Telescope provide us with information about the atmosphere, allowing us to simulate whether the physical processes that lead to lightning can occur. Our results show that this process can indeed take place in the atmospheres we studied," says Elloise Fangel-Lloyd. She is a scientist at the Danish Meteorological Institute (DMI) and conducted this work as a doctoral student at the Technical University of Denmark (DTU).
She is the lead author of a paper presenting these findings, which has just been published in the journal Scientific Reports (part of the Nature portfolio).
Small electrical discharges could be the start of lightning
The researchers simulated phenomena known as streamers.
These are small electrical discharges that typically represent the initial stages of lightning formation. Thus, the researchers did not simulate a full lightning strike, but rather the process that can initiate its formation.
The simulations show that the discharges capable of triggering lightning can occur in all three potential atmospheric compositions of the exoplanet investigated by the researchers.
Lightning could form more easily there than on Earth
The calculations also show that electrical breakdown in the modeled atmospheres requires only about half the electric field strength needed on Earth.
The results therefore suggest that the atmosphere of K2-18b may be more conducive to lightning formation than Earth's atmosphere.
"An electric field exerts a force on electrically charged particles. If the field becomes strong enough, the gas in the atmosphere can become ionized; this enables the creation of electrical discharges that can lead to lightning," says Christoph Köhn, a lead researcher at the Department of Physics at TU Dortmund and the Department of Astrophysics and Atmospheric Physics at DTU, and co-author of the study.
"What is particularly interesting here is that we can use our knowledge of electrical discharges on Earth to investigate the processes that might be taking place in the atmosphere of a planet many light-years away."
The researchers' simulations also show that an atmosphere's water vapor content influences how easily the process leading to lightning can be triggered.
Once lightning has formed, it can influence an atmosphere's chemistry, thereby affecting potential life and habitability - both on a planet like K2-18b and on other exoplanets.