- 4538 - EXOPLANET - discovered about to crash? - 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?
------------------------------- 4538
- EXOPLANET -
discovered about to crash?
-
Astronomers are investigating 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. This 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.
-
- 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”.
-
- 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-6255 b also experiencing the tidal disruption, which is a common
occurrence throughout the cosmos, including black holes.
-
- 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.
-
- 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. While intriguing,
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, and 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.
But what is the significance of TOI-6255 b being an Earth-sized planet as
opposed to a Jupiter-sized planet, or larger?
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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.
-
- 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.
-
- 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.
-
- One similarity between our solar system and
exoplanetary systems is the Roche limit. However, the study also focuses on
tidal disruption that is physically distorting TOI-6255 b. Tidal disruption
could be a potential fate of rocky planets.
-
- 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.
-
-
August 19, 2024 EXOPLANET -
discovered about to crash? 4538
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--------------------- --- Tuesday, August 20,
2024
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