Radio signals from distant stars suggest hidden planets

Date:
October 11, 2021
Source:
University of Queensland
Summary:
Using the world's most powerful radio antenna, scientists have
discovered stars unexpectedly blasting out radio waves, possibly
indicating the existence of hidden planets.



FULL STORY ========================================================================== Using the world's most powerful radio antenna, scientists have discovered
stars unexpectedly blasting out radio waves, possibly indicating the
existence of hidden planets.


==========================================================================
The University of Queensland's Dr Benjamin Pope and colleagues at the
Dutch national observatory ASTRON have been searching for planets using
the world's most powerful radio telescope Low Frequency Array (LOFAR)
situated in the Netherlands.

"We've discovered signals from 19 distant red dwarf stars, four of
which are best explained by the existence of planets orbiting them,"
Dr Pope said.

"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.

"This discovery is an important step for radio astronomy and could
potentially lead to the discovery of planets throughout the galaxy." Previously, astronomers were only able to detect the very nearest stars
in steady radio emission, and everything else in the radio sky was
interstellar gas, or exotica such as black holes.



==========================================================================
Now, radio astronomers are able to see plain old stars when they make
their observations, and with that information, we can search for any
planets surrounding those stars.

The team focused on red dwarf stars, which are much smaller than the Sun
and known to have intense magnetic activity that drives stellar flares
and radio emission.

But some old, magnetically inactive stars also showed up, challenging conventional understanding.

Dr Joseph Callingham at Leiden University and ASTRON and lead author of
the discovery, said that 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.

"Our own Earth has aurorae, 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," he said.



==========================================================================
"But in the case of aurorae from Jupiter, they're much stronger as its
volcanic moon Io is blasting material out into space, filling Jupiter's environment with particles that drive unusually powerful aurorae.

"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.

"It's a spectacle that has attracted our attention from lightyears away."
The research team now wanted to confirm the proposed planets do exist.

"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.

"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."
The discoveries with LOFAR are just the beginning, but the telescope
only has the capacity to monitor stars that are relatively nearby,
up to 165 lightyears away.

With Australia and South Africa's Square Kilometre Array radio telescope finally under construction, hopefully switching on in 2029, the team
predict they will be able to see hundreds of relevant stars out to much
greater distances.

This work demonstrates that radio astronomy is on the cusp of
revolutionising our understanding of planets outside our Solar System.

========================================================================== Story Source: Materials provided by University_of_Queensland. Note:
Content may be edited for style and length.


========================================================================== Journal References:
1. Callingham et al. The population of M dwarfs observed at low radio
frequencies. Nature Astronomy, 2021 [abstract]
2. Benjamin J.S. Pope, Joseph R. Callingham, Adina D. Feinstein,
Maximilian
N. Gu"nther, Harish K. Vedantham, Megan Ansdell, & Timothy
W. Shimwell.

The TESS View of LOFAR Radio-Emitting Stars. Astrophysical Journal
Letters, 2021 DOI: 10.3847/2041-8213/ac230c ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/10/211011110806.htm

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