Astronomers detect repeating radio signal from Earth-sized exoplanet

The Earth’s magnetic field protects the planet’s atmosphere, essential for life to survive, by deflecting energy particles and plasma that emanate from the sun. Finding atmospheres around planets outside our solar system could point to other worlds that could potentially support life, CNN says.

Scientists noticed strong radio waves from the star YZ Ceti and a rocky exoplanet orbiting it, called YZ Ceti b, while observing with the Carl G. Jansky Very Large Array of Telescopes in New Mexico. The researchers believe that the radio signal was created as a result of the interaction between the planet’s magnetic field and the star.

The study, detailing the findings, was published on Monday in the journal Nature Astronomy.

“We saw the initial surge and it looked beautiful,” study lead author Sebastian Pineda, a research astrophysicist at the University of Colorado Boulder, said in a statement. “When we saw it again, it was very revealing that, okay, maybe we really have something here.”

According to Pineda, magnetic fields could prevent the planet’s atmosphere from shrinking and being substantially destroyed over time as particles are released from the star and bombard it.

In order for radio waves to be detectable on Earth, they must be very strong, the researchers say.

“Whether a planet survives with or without an atmosphere may depend on whether the planet has a strong magnetic field or not,” says Sebastian Pineda.

Previously, researchers have detected magnetic fields on exoplanets similar in size to Jupiter, the largest planet in our solar system. But finding magnetic fields on planets smaller than Earth is more difficult because the magnetic fields are virtually invisible.

“What we’re doing is looking for a way to see them,” study co-author Jackie Villadsen, an assistant professor of physics and astronomy at Bucknell University in Pennsylvania, said in a statement.

“We are looking for planets that are really close to their stars and similar in size to Earth,” she said. “These planets are too close to their stars to be a place where you could live, but because they are so close, the planet sort of pushes through a bunch of stuff coming from the star. If a planet has a magnetic field and passes through enough stellar matter, it will cause the star to emit bright radio waves.”

As CNN notes, the planet YZ Ceti b takes only two Earth days to complete one revolution around its star. Meanwhile, the shortest orbit in our solar system is the planet Mercury, which takes 88 Earth days to make a complete revolution around the Sun.

As the exoplanet YZ Ceti b orbits its star, the star’s plasma collides with the planet’s magnetic field, bounces off and interacts with the star’s magnetic field. All of these energy reactions create and emit strong radio waves that can be found on Earth.

The researchers measured the radio waves they detected to determine the strength of the planet’s magnetic field.

“This gives us new information about the environment around stars,” says Sebastian Pineda. “This idea is what we call “extrasolar space weather.”

In our solar system, solar activity can create space weather that impacts the Earth. Energy bursts from the sun can disrupt satellites and global telecommunications and cause dazzling light shows near the Earth’s poles, such as the northern lights.

Scientists speculate that the interaction between YZ Ceti and its planet also creates the aurora, but this light show actually takes place on a star.

“We do see an aurora on a star — that’s what this radio emission is,” Pineda said. “The planet should also have an aurora if it has its own atmosphere.”

The researchers believe that YZ Ceti b is the best candidate discovered so far for the role of a rocky exoplanet with a magnetic field.

“That may indeed be true,” Villadsen notes. “But I think it will take a lot of follow-up work before there is really conclusive confirmation of radio waves caused by the planet.”

New radio telescopes set to become operational this decade could help astronomers detect signals indicative of magnetic fields more frequently, the researchers say.

“The search for potentially habitable worlds in other solar systems depends in part on being able to determine whether rocky Earth-like exoplanets actually possess magnetic fields,” said Joe Pesce, program director at the National Radio Astronomy Observatory, in a statement. “This study not only shows that this particular rocky exoplanet is likely to have a magnetic field, but also provides a promising method for finding more.”