Around a small star, an exoplanet the size of Jupiter developed. A giant
planet the size of Jupiter has been discovered circling a tiny, low-mass
star, startling scientists and casting doubt on beliefs about how planets
develop.
The red dwarf TOI-4860 circles the extrasolar planet, also known as an
exoplanet. TOI-4860, which is in the constellation Corvus, has a mass that
is just around one-third that of the sun. The exoplanet in question,
TOI-4860 b, is suitably named since it orbits its star roughly once every
1.5 Earth days, making it a "warm Jupiter."
For two reasons, this is rare.
First, planets like this one aren't intended to develop around low-mass
stars; their widths are about similar to that of Jupiter. Second, a
significant percentage of metals, which astronomers use to refer to elements
heavier than hydrogen and helium, appear to be concentrated in TOI-4860
b.
"Under the canonical planet formation model, the less mass a star has, the
less massive is the disk of material around that star," team member and
Ph.D. candidate at the University of Birmingham, George Dransfield,
said in a release. "High-mass planets like Jupiter were generally believed not to exist
since planets are formed from that disk. However, we were interested in this
and sought to investigate planetary prospects to determine whether it was
feasible. Our first confirmation comes from TOI-4860, which is also the
lowest mass star to support a planet with such a high mass.
NASA's Transiting Exoplanet Survey Satellite (TESS), which seeks planets
outside the solar system by looking for minute variations in the brightness
of light produced by stars, was the first to discover TOI-4860 b. These dips
occur when a planet in orbit crosses or transits its parent star.
Following this encounter, Dransfield and colleagues continued to monitor
the system using the SPECULOOS South Observatory to search for habitable
planets eclipsing ultra-cool stars. Speculos utilizes the same methodology
as TESS to look for exoplanets, but it concentrates on dim, cold stars. As a
result, instead of much bigger gas giants like TOI-4860 b, the facility
located at the
Paranal Observatory
in Chile's Atacama Desert typically searches for Earth-size planets.
The scientists saw the planet using SPECULOOS as it emerged from and
vanished behind its star. This observation was then followed up on by
teammates using the Subaru Telescope in Hawaii.
It is unclear how such a massive exoplanet got to circle a low-mass star,
but information on TOI-4860 b's makeup may provide some insight.
Amaury Triaud, a professor at the University of Birmingham and the team's
head, claimed that the planetary features, which seem unusually richer in
heavy metals, may contain a clue as to what may have happened. "We have
found a similar phenomenon in the host star as well."
Triaud continued by saying that it's probable that the planet's development
was accelerated by the presence of heavy elements.
Given TOI-4860 b's short orbital period and the high metallicity of its
parent star, this system may be especially helpful for researching the warm
Jupiters' atmospheres and better understanding how these gas giants
form.
The team that discovered this exoplanet now plans to use the Very Large
Telescope (VLT), situated in the Atacama Desert of northern Chile, to look
for similar planets orbiting tiny parent stars.
I will always be grateful to our team's talented Ph.D. students for
suggesting that we examine systems like TOI-4860, Triaud said in his
conclusion. Since planets like TOI-4860 b are essential to improving our
understanding of planet formation, their labors have really paid off.
The discovery of the new exoplanet was documented in a paper
published Aug. 4 in the journal
Monthly Notices of the Royal Astronomical Society: Letters.
