Nineteen new red dwarf stars discovered that may harbor exoplanets

The explosive stars unexpectedly emit radio waves. And that may indicate unknown worlds.

Astronomers are still eagerly searching for exoplanets; planets outside our solar system. But it is not so easy to bring such distant, hidden worlds to light. In a new study, scientists have applied a fairly new technique by searching for auroras in red dwarf stars. And surprisingly, that turns out to be very successful.

radio waves

In the study, the researchers enlisted the help of the Netherlands-led Low Frequency Array (LOFAR) radio telescope. This is the most powerful radio telescope in the world, with the center in Exloo in Drenthe. The investigation leads to the discovery of 19 red dwarf stars that unexpectedly emit radio waves. These eruptions may be caused by interaction with exoplanets.

aurora

What exactly is that? Astronomers have known for some time that some planets, like our Earth, emit powerful radio waves when their magnetic fields collide with the solar wind. “With our Earth, you have northern lights and southern lights,” explains researcher Joe Callingham. “At Jupiter, the aurora is even more intense because the volcanic moon Io is blowing a lot of material toward Jupiter.” The researchers’ models show that something similar may be going on in the nineteen stars studied as in Jupiter’s aurora. “The aurora on the star is then caused by an exoplanet near the star blowing a lot of material into space,” said researcher Harish Vedantham.

The existence of interactions between a star and its planet has been predicted for more than thirty years. Yet only recently have astronomers been able to distinguish the associated radio waves. The movement of a planet through the strong magnetic field of a red dwarf acts like an electric motor, similar to the dynamo of a bicycle. This creates a strong current that drives auroras and radio emissions on the star.

An artistic rendering of aurora near a red dwarf star (left) due to interaction with an exoplanet (right). Image: Danielle Futselaar

It means that the aurora near the 19 red dwarf stars studied is hinting at hidden exoplanets. With four stars, the signals are best explained by the fact that those stars interact with as yet unconfirmed exoplanets orbiting them.

Last year

The work builds on a study last year, when the same team discovered the first aurora near a star. At the time, the researchers found anomalous radio waves from the red dwarf star GJ115, which appeared to point to a hidden exoplanet orbiting the star. The exciting research left me wanting more. And now the team is using the knowledge gained back then to reveal more exoplanets using the same method.

The researchers are now subjecting the nineteen red dwarf stars to a closer examination. For example, they use optical telescopes to see if they see clues to exoplanets and they search for patterns in the radio radiation. In the future, the team also wants to enlist the help of the Square Kilometer Array (SKA), which is still under construction, the largest radio telescope on Earth. This telescope is expected to be commissioned by the end of the next decade.