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Astronomers have unearthed a huge gas giant planet with the density of a
marshmallow, which is encircling a cool red dwarf star situated 580
light-years from Earth.
The Jupiter -like exoplanet is the lowest-density world ever seen
orbiting a red dwarf, reports Space.com.
Red dwarf stars are the tiniest and dimmest stars and are still
converting hydrogen to helium in their cores via nuclear fusion, which
is a part of the star's life named "the main sequence".
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Despite being much cooler than the sun, red dwarfs are very active and
send out powerful flares, which can strip the atmospheres of any
orbiting planet.
These violent eruptions make a red dwarf star system a seemingly
unlikely and inhospitable place to find a fluffy exoplanet, like the
newly discovered world, dubbed TOI-3757 b.
The planet is so near to its red dwarf parent star that it undertakes an
entire orbit in only 3.5 Earth days, which is 25 times faster than the
closest planet to the Sun - Mercury.
It's considerably larger than Jupiter - the solar system's biggest
planet - with a diameter of approximately 100,00 miles (150,000
kilometres).
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Shubham Kanodia, the lead study author and an astronomer at the Carnegie
Institution in Washington, D.C, said in a statement from the National
Science Foundation's NOIRLab, which operates some of the telescopes used
in the research, that: "Giant planets around red dwarf stars have
traditionally been thought to be hard to form.
"So far this has only been looked at with small samples from Doppler
surveys, which typically have found giant planets further away from
these red dwarf stars."
He added: "Until now we have not had a large enough sample of planets to
find close-in gas planets in a robust manner."
Kanodia thinks they might be able to explain how a low-density gas giant
formed in such extreme and harsh conditions.
They suggest the low density of TOI-3757 b is the result of two main
factors.
The first factor relates to how gas giants start their formation.
They have huge rocky centers, about 10 times the mass of Earth, which
quickly suck in large amounts of surrounding gas to become Jupiter-like
worlds.
The team thinks the lower abundances of heavy elements in the red dwarf
star that TOI-3757 b circulates means the rocky core of this exoplanet
could have formed more slowly.
This would have delayed the accretion of gas to the rocky core with an
impact on TOI-3757 b's overall density after formation.
Secondly, the astronomers think that the orbit of TOI-3757 b is slightly
elliptical.
It's like a flattened circle, meaning at moments it is closer to its red
dwarf parent star.
These closest approaches result in excessive heating of the planet which
causes its atmosphere to bloat.
TOI-3757 b was initially discovered by NASA's Transiting Exoplanet
Survey Satellite (TESS) mission, which spots exoplanets via the tiny dip
in the light of parent stars.
TOI-3757 b is less than half as dense as Saturn, which is the
lowest-density planet in the solar system and is about one-quarter the
density of water. |