Dutch radio telescope discovers exoplanet – NRC

GJ 1151, a red dwarf star only 26 light-years away, is probably an earth-like planet orbiting. This follows from observations with the LOFAR radio telescope led by the Netherlands. This instrument detects – for the first time – radio radiation that is characteristic of the interaction between a planet and the magnetic field of its mother star.

Fast electrons

“The radio emission that we see is caused by the same electrons that produce polar light,” Harish Vedantham explains by email. Vedantham is a staff astronomer at ASTRON, the Dutch institute for radio astronomy, and lead author of the research report that was published on Monday Nature Astronomy popped up. “Two ingredients are needed for this: an object with a strong magnetic field – in this case a star – and electrons that move along the magnetic field lines at high speeds.”

This raises the question of where these electrons derive their high speed. “We have previously observed similar emissions with planets in our solar system, such as Jupiter,” says Vedantham. In the case of Jupiter, the fast rotation of the planet plays a role in this, but with star GJ 1151 this cannot be the case: it rotates slowly. With Jupiter, however, there is a second way to accelerate electrons: the interaction with its near moon. In addition, it is the movement of Io within the strong magnetic field of the planet that is responsible for the acceleration of the electrons.

“The latter is what we think happens at GJ 1151, the magnetic interaction between a star and its planet,” Vedantham summarizes. The principle is comparable to the operation of a bicycle dynamo.

The astronomers were helped in their discovery by the fact that GJ 1151 is a “quiet” red dwarf star. Some of his peers produce violent outbursts, which also release radio radiation. And that can mask the “planet signal”.

Small and cool

Red dwarf stars are smaller and cooler than our sun, and especially very numerous. Fifty of the sixty nearest stars are red dwarfs, and it has been found that the planets orbiting around such stars are usually on the small side. “That means” Earth 2.0 “is probably circling around a red dwarf,” said Vedantham. “But the question is what impact the strong magnetic field of a red dwarf has on the quality of life on such a planet. Radio emissions as we have now observed them can help answer this question. “

Not much is known about the now discovered planet. The observed emission fits a planet the size of the earth with a turn-around time of 1 to 5 days. But it could also be a smaller planet with a shorter orbit or a larger planet with a longer orbit. What is certain is that the planet of GJ 1151 must be lighter than five earth masses. Otherwise the red dwarf would have to show a clearly measurable rocking movement, and that is not the case.

– .