- 4558 -
STARS DEVOUR PLANETS ?
- Astronomers have confirmed
the existence of exoplanets with extremely small orbits around their stars. But
what about exoplanets that get close enough to be devoured by their star, and
what if it’s an Earth-sized exoplanet?
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-------------------------------------- 4558
- STARS DEVOUR
PLANETS ?
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- Researchers investigated an Earth-sized
exoplanet with an orbital period of only 5.7 hours, known as
“ultra-short-period” (USP) exoplanets, that could eventually experience what’s
known as “tidal disruption”, resulting in its devourment by its star.
-
- “Tidal disruption” could be a potential
fate of rocky planets. It seems like
about 10 percent of sun-like stars might have engulfed their rocky planets. The
system TOI-6255 is the best-known progenitor for those planet engulfment
events. The tidal disruption of rocky planets allows us to probe their interior
composition and compare with Earth.
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- The researchers analyzed TOI-6255 b, whose
radius is ~1.08 and mass is ~1.44 of Earth’s and located just over 20.4 parsecs
(65.2 light-years) from Earth. However, while being Earth-sized holds promise
for life, TOI-6255 b’s 5.7-hour orbit not only make this exoplanet far too hot
for life as we know it to exist, but this also means its orbit takes it
dangerously close to what’s known as “Roche limit”.
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- The “Roche limit” is the distance a smaller
object can orbit a larger object until the larger object’s gravity tears the
smaller object to pieces, along with “TOI-6255b” also experiencing the tidal disruption, which is a common
occurrence throughout the cosmos, including black holes.
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- This planet is doomed for tidal disruption
in 400Myr which is short on cosmic scale (~13Gyr). The planet is also tidally
distorted to be football like in shape (10 percent deviation from sphere), in
comparison Earth’s tidal distortion due to the moon is only 1e-7 [0.0000001]
level.
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- “Orbital phase curve” study of this planet
could confirm that it is indeed tidally distorted. We know what the phase curve
should look like for a spherical planet, tidally distorted planet has a strong
deviation from that. We can also see if the surface of the planet is covered by
lava pool as would be expected on a planet this hot.
-
- “ USPs” are exoplanets whose orbits are less
than one day and whose masses are less than 2x the Earth. Only about 100 USPs have been discovered
with a 2014 study estimating approximately 0.5 percent exist around Sun-like
stars and a 2019 study discussing their bulk composition (i.e., mass of its
iron core and mantle). Given their
extremely short orbit, these worlds are likely too hot for life as we know it
to exist.
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- Along with USPs are the familiar “hot
Jupiters” who orbit their stars in only a few days and astronomers estimate
their population is in the hundreds.
These worlds are Jupiter-sized or larger gas planets and are also
potentially far too hot for life as we know it to exist.
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- Planets similar to Earth in size are most
likely rocky, mostly made of iron core and silicate mantle. They show us what
terrestrial planets in other planetary systems are made of. Jupiter-sized
planets are most certainly covered by thick hydrogen and helium atmospheres.
Jupiter-sized planets are unlikely to harbor life.
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- While TOI-6255 b isn’t due for disassembly
for another 400 million years, watching any exoplanet get ripped to shreds by
its host star could provide important insights regarding the planet’s exterior
and interior compositions, thus helping us better understand the similarities
between exoplanets and planets within our own solar system.
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- These unique worlds and their extremely
tight orbits have challenged our understanding of solar system architecture
throughout our Milky Way Galaxy, as Mercury is the closest planet to our Sun,
and it still takes 88 days to complete one orbit.
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- Tidal disruption of planets is minimal in
our solar system. However, the rings of Saturn are thought to originate from
tidal disruption of satellites around Saturn. Tidal forces are strongly
dependent on orbital separation, only objects with the shortest orbital period
experience significant tides.
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-
September 17, 2024 STARS
DEVOUR PLANETS ? 4558
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------ “Jim Detrick” -----------
--------------------- --- Wednesday, September
18, 2024
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