- 4573 - EXOPLANETS - and Pluto dwarf planet? - 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?
----------------------------------- 4573
- EXOPLANETS
- and Pluto dwarf planet?
-
- 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. 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.
-
- 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. 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?
-
- 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. 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.
-
- Discovered in 1930, Pluto was long
considered our solar system's ninth planet. But after the discovery of similar
worlds deeper in the Kuiper Belt, Pluto was reclassified as a “dwarf planet”.
-
- A dwarf planet is an object in orbit around
the Sun that is large enough to pull itself into a nearly round shape but has
not been able to clear its orbit of debris.
Pluto falls into the dwarf planet category because it is located in a
part of our solar system known as the Trans-Neptunian region (beyond Neptune)
where other objects might cross Pluto's orbital path.
-
- Pluto is only about 1,400 miles wide. At
that small size, Pluto is only about half the width of the United States. It's
about 3.6 billion miles away from the Sun, and it has a thin atmosphere
composed mostly of nitrogen, methane, and carbon monoxide. On average, Pluto’s
temperature is -387°F (-232°C), making it too cold to sustain life.
-
- Pluto is orbited by five known moons, the
largest of which is Charon. Charon is about half the size of Pluto itself,
making it the largest satellite relative to the planet it orbits in our solar
system. Pluto and Charon are often referred to as a "double planet."
-
- The only spacecraft to explore Pluto up
close was NASA's New Horizons. It flew by the dwarf planet and its moons in
2015.
-
- In 1930, Venetia Burney of Oxford, England,
suggested to her grandfather that the new discovery be named for the Roman god
of the underworld. He forwarded the name to the Lowell Observatory and it was
selected.
-
- The surface of Pluto is extremely cold, so
it's unlikely that life could exist there. At such cold temperatures, water,
which is vital for life as we know it, is essentially rock-like. Pluto's
interior is warmer, however, and some think there could even be an ocean deep
inside.
-
- Pluto has an equatorial diameter of about
1,477 miles (2,377 kilometers). Pluto is about 1/5th the width of Earth. From an average distance of about 3.7
billion miles (5.9 billion kilometers), Pluto is about 39 times farther away
than the Earth is from the Sun. From this distance, it takes sunlight 5.5 hours
to travel from the Sun to Pluto.
-
- If you were to stand on the surface of Pluto
at noon, the Sun would be 1/900 the brightness it is here on Earth, or about
300 times as bright as our full moon. There is a moment each day near sunset
here on Earth when the light is the same brightness as midday on Pluto.
-
- Pluto's orbit around the Sun is unusual
compared to the planets: it's both elliptical and tilted. Pluto's
248-year-long, oval-shaped orbit can take it as far as 49.3 astronomical units
(AU) from the Sun, and as close as 30 AU. (One AU is the mean distance between
Earth and the Sun: about 93 million miles or 150 million kilometers.) But on
average, Pluto is 3.7 billion miles away
from the Sun, or 39 AU.
-
- From 1979 to 1999, Pluto was near
perihelion, when it is closest to the Sun. During this time, Pluto was actually
closer to the Sun than Neptune. One day
on Pluto takes about 153 hours. Its axis of rotation is tilted 57 degrees with
respect to the plane of its orbit around the Sun, so it spins almost on its
side. Pluto also exhibits a retrograde rotation; spinning from east to west
like Venus and Uranus.
-
- Pluto has five known moons: Charon, Nix,
Hydra, Kerberos, and Styx. This moon system might have formed by a collision
between Pluto and another similar-sized body early in the history of the solar
system.
-
- Charon, the biggest of Pluto's moons, is
about half the size of Pluto itself, making it the largest satellite relative
to the planet it orbits in our solar system. It orbits Pluto at a distance of
just 12,200 miles. Our Moon is 20 times
farther away from Earth. Pluto and Charon are often referred to as a double
planet.
-
- Charon's orbit around Pluto takes 153 hours
– the same time it takes Pluto to complete one rotation. This means Charon
neither rises nor sets, but hovers over the same spot on Pluto's surface. The
same side of Charon always faces Pluto, a state called “tidal locking”.
-
- Pluto's other four moons are much smaller,
less than 100 miles wide. They're also irregularly shaped, not spherical like
Charon. Unlike many other moons in the solar system, these moons are not
tidally locked to Pluto. They all spin and don’t keep the same face towards
Pluto.
-
- Dwarf planet Pluto is a member of a group
of objects that orbit in a disc-like zone beyond the orbit of Neptune called
the Kuiper Belt. This distant realm is populated with thousands of miniature
icy worlds, which formed early in the history of our solar system about 4.5
billion years ago. These icy, rocky bodies are called Kuiper Belt objects,
transneptunian objects, or plutoids.
-
- Pluto is about two-thirds the diameter of
Earth's Moon and probably has a rocky core surrounded by a mantle of water ice.
Interesting ices like methane and nitrogen frost coat the surface. Due to its
lower density, Pluto's mass is about one-sixth that of Earth's Moon.
-
- Pluto's surface has mountains, valleys,
plains, and craters. The temperature on Pluto can be as cold as -375 to -400
degrees Fahrenheit . Pluto's tallest
mountains are 6,500 to 9,800 feet (2 to 3 kilometers) in height. The mountains
are big blocks of water ice, sometimes with a coating of frozen gases like
methane. Long troughs and valleys as long as 370 miles add to the interesting
features of this faraway dwarf planet.
-
- Craters as large as 162 miles (260
kilometers) in diameter dot some of the landscape on Pluto, with some showing
signs of erosion and filling. This suggests tectonic forces are slowly
resurfacing Pluto. The most prominent
plains observed on Pluto appear to be made of frozen nitrogen gas and show no
craters. These plains do show structures suggesting convection (blobs of
material circulating up and down).
-
- Pluto has a thin, tenuous atmosphere that
expands when it comes closer to the Sun and collapses as it moves farther away,
similar to a comet. The main constituent is molecular nitrogen, though
molecules of methane and carbon monoxide have also been detected.
-
- When Pluto is close to the Sun, its surface
ices sublimate (changing directly from solid to gas) and rise to temporarily
form a thin atmosphere. Pluto's low gravity (about 6% of Earth's) causes the
atmosphere to be much more extended in altitude than our planet's atmosphere.
Pluto becomes much colder during the part of each year when it is traveling far
away from the Sun. During this time, the bulk of the planet's atmosphere may
freeze and fall as snow to the surface.
-
- It isn't known whether Pluto has a magnetic
field, but its small size and slow rotation suggest little or none.
-
-
October 9, 2024 PLANET
DISCOVERED - and Pluto renamed? 4573
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--------------------- --- Wednesday, October 9,
2024
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