In a major discovery, astronomers have for the first time detected stars that are blasting radio signals hinting at the presence of hidden planets around them. The signals were picked up using the world’s most powerful radio antenna, the Low-Frequency Array (LOFAR) situated in the Netherlands.

The new technique of spotting hidden planets could hint at the possibility of life in the system, which remains the biggest question in astronomy. Are we alone? The signals were detected by Dr Benjamin Pope from the University of Queensland and his colleagues at the Dutch national observatory ASTRON. The astronomers have been searching for planets using LOFAR.

The astronomers have detected signals from 19 distant red dwarfs, four of which are best explained by the existence of planets orbiting them. “We’ve long known that the planets of our own solar system emit powerful radio waves as their magnetic fields interact with the solar wind, but radio signals from planets outside our solar system had yet to be picked up,” the astronomers said in a statement.

Earlier, astronomers were only able to detect the very nearest stars in steady radio emission while everything else in the radio sky was interstellar gas or black holes. Radio astronomers are now able to see plain old stars when they make their observations as the team focussed on red dwarf stars, which are much smaller than the Sun and known to have an intense magnetic activity that drives stellar flares and radio emission.

In a study published in Nature Astronomy, the team is confident these signals are coming from the magnetic connection of the stars and unseen orbiting planets, similar to the interaction between Jupiter and its moon, Io. Dr Joseph Callingham at Leiden University, ASTRON and lead author of the discovery said, “Our own Earth has auroras, commonly recognised here as the northern and southern lights, that also emit powerful radio waves this is from the interaction of the planet’s magnetic field with the solar wind.”

Researchers designed a model to study the interaction of the magnetic field with the solar wind just as it happens between Jupiter and its Moon Io that drives auroras on the largest planet in the solar system. These auroras are much stronger than the ones we see on Earth.

They then scaled up the model to detect radio emissions from distant stars.

“Our model for this radio emission from our stars is a scaled-up version of Jupiter and Io, with a planet enveloped in the magnetic field of a star, feeding material into vast currents that similarly power bright aurorae,” the team said. While lightyears away, these magnetic interactions indicate the presence of stars and planets hidden in their system.

“We can’t be 100 per cent sure that the four stars we think have planets are indeed planet hosts, but we can say that a planet-star interaction is the best explanation for what we’re seeing,” Dr Pope said.

He added that follow-up observations have ruled out planets more massive than Earth, but there’s nothing to say that a smaller planet wouldn’t do this.

Stating that the discovery is an important step for radio astronomy and could potentially lead to the discovery of planets throughout the galaxy, the researchers await the launch of under construction Square Kilometre Array radion telescope by 2029 that will “help see hundreds of relevant stars out to much greater distances.”