3901 -
FORBIDEN PLANETS - too
big for their sun? Massive 'forbidden
planet' orbits a strangely tiny star only 4 times its size The discovery could challenge our theories of
how gas giants like Jupiter form.
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------------ 3901 - FORBIDEN PLANETS - too big for their sun?
- Massive
'forbidden planet' orbits a strangely tiny star only 4 times its size The discovery could challenge our theories of
how gas giants like Jupiter form.
-
- Astronomers
have discovered an unusual planetary system consisting of a Jupiter-sized
planet orbiting a tiny star that is only four times the size of the solar
system gas giant. This could challenge theories of how gas giant planets form.
-
- The
exoplanet orbits a red dwarf star designated “TOI 5205” that is much cooler and
smaller than the sun. The small size and relatively cool temperatures of these
M-dwarf stars, the most common type of stellar body in the Milky Way, make them
redder than the sun.
-
- The discovery
of this exoplanet using NASA's “Transiting Exoplanet Survey Satellite” (TESS)
telescope challenges that concept. The planet was confirmed and characterized
by the team using various ground-based telescopes and instruments.
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- The host
star is just about four times the size of Jupiter, yet it has somehow managed
to form a Jupiter-sized planet. Though
gas giants have been discovered around M dwarf stars before, none of them have
been discovered orbiting such a low mass example of this class of star.
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- Planets are
created in spinning discs of gas and dust called "protoplanetary
discs" that surround young stars. This material is the remains of the same
matter that collapsed to birth its central star. When dense patches collapse
under their own gravity planet cores are born and they then collect more
material.
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- Current
planet formation models suggest that to birth a gas giant it takes material
equivalent to 10 times the mass of Earth. This first forms a rocky core and
this core goes on to accumulate gas to form the disc to grow a giant planet.
This process has to occur quickly.
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- In the
beginning, if there isn't enough rocky material in the disk to form the initial
core, then one cannot form a gas giant planet. And at the end, if the disk
evaporates away before the massive core is formed, then one cannot form a gas
giant planet.
-
- And yet
TOI-5205b formed despite these guardrails.
Based on our nominal current understanding of planet formation,
TOI-5205b should not exist; it is a 'forbidden' planet."
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- To picture
how unbalanced this system is to planetary systems that astronomers expect,
imagine our star the sun squashed down to the size of a grapefruit. That size
reduction would mean the largest gas giant in our solar system, Jupiter, would
be about the size of a garden pea.
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- The
TOI-5205 system is more like a pea orbiting a lemon.
-
- The size
disparity in the size is so great that when TESS used the drop in light caused
by a planet as it passes in front of its star, known as the transit method,
that dip in light was 7% of the star's total light output.
-
- That makes
the dimming of TOI-5205 by this Jupiter-sized exoplanet the largest known drop
in light caused by an exoplanet transit.
This extreme dip in light or technically, "large transit
depth,".
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- Observations
with the James Webb Space Teleacope could help determine the composition of
TOI-5205 b's atmosphere and may shed light on the processes that birthed this
"forbidden" planet.
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- The total dust
and gas for a postulated protoplanetary disc around a
0.392 solar mass red dwarf could be 1.305136E+03 earth
masses. The 1.08 exoplanet is about
343.2456 earth masses.
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- Are we
absolutely certain that it is a "rocky" gas giant? Why not a binary
star that has failed to form because of a lack of total mass?
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- With the
number of stars out there, even wildly improbably configurations are going to
exist in abundance. Maybe this system only existed because of a sequence of
unique gravitation interactions.
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- Theories may
be too rigid, but not entirely wrong. Also, we must take great care in
exoplanet analysis because the data is skewed towards what is easiest to
detect...
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March 5, 2023 FORBIDEN
PLANETS - too big for their sun? 3901
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--- Sunday, March 5, 2023
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