- 4115 - ROGUE PLANETS - roaming without a sun? There could be trillions of “Rogue Planets” wandering the Milky Way galaxy? Rogue planets are free-floating exoplanets that drift through space unbound by the gravitational tug of a star. They can form within their own solar system and get ejected, or they can form independently.
-------------- 4115 - ROGUE PLANETS - roaming without a sun?
- This is the second discovery of an
Earth-mass rogue planet, the first being discovered in September 2020, while
the second study examines the potential number of rogue planets that could
exist in our Milky Way Galaxy.
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- They estimate that our galaxy is home to 20
times more rogue planets than stars, trillions of worlds wandering alone. This is the first measurement of the number
of rogue planets in the galaxy that is sensitive to planets less massive than
Earth.
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- This research builds upon a previous
hypothesis that the number of rogue planets could be greater than the number of
stars within our galaxy, and is the result of a nine-year survey called” MOA”
(Microlensing Observations in Astrophysics). Current estimates state at least
100 billion stars exist in the Milky Way Galaxy which means there could be at
least 2 trillion rogue planets randomly floating throughout our tiny corner of
the universe.
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- The Earth-mass rogue was found with the
microlensing method like the first discovery. This detection method involves
using a gravitationally strong object, traditionally a star, to act as a
gravitational lens that bends any light traveling from behind it towards Earth,
which astronomers can then observe using these warped light waves. In the case
of rogue planets, the planet uses its own gravitational field to be observed
when passing in front of a distant star.
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- Microlensing is the only way we can find
objects like low-mass free-floating planets and even primordial black
holes. These two studies are preludes
to what the “Nancy Grace Roman Space Telescope” (previously named the Wide-Field
Infrared Survey Telescope, or WFIRST) will accomplish, which currently has a
contracted launch date of October 2026.
Shortened as “Roman”, this NASA-built infrared space telescope will be
located at the Sun-Earth L2 Lagrange Point, which is located on the opposite
side of the Earth from the Sun.
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- Once there, Roman will spend its 5-year
mission trying to answer some of the universe’s most profound questions,
specifically pertaining to dark matter and dark energy, the theory of general
relativity, and searching for exoplanets using the microlensing method. There
could be up to 400 Earth-mass rogue planets just within our Milky Way.
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- “Roman” will be sensitive to even
lower-mass rogue planets since it will observe from space. The combination of Roman’s wide view and
sharp vision will allow astronomers to study the objects it finds in more
detail than we can do using only ground-based telescopes.
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- One big question about Earth’s formation
is, where did all the water come from? New data from the James Webb Space
Telescope (JWST) shows newly forming planets in a system 370 light-years away
are surrounded by water vapor in their orbits.
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- The distant planetary system, named “PDS
70”, contains both an inner disk and outer disk of gas and dust, separated by a
5 billion-mile-wide gap. JWST’s MIRI (Mid-Infrared Instrument) detected the
water vapor in the system’s inner disk, where rocky terrestrial and sub-Neptune
planets are expected to form.
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- The water vapor was detected at distances
of less than 100 million miles from the star. Earth orbits 93 million miles
from our Sun. While actual planets
haven’t yet been detected in this inner region of PDS 70, astronomers have seen
evidence of protoplanets, with the raw materials for building rocky worlds in
the form of silicates. The detection of water vapor implies that if rocky
planets are forming there, they will have water available to them from the very
start.
-
- A spectrum of the protoplanetary disk of
PDS 70, obtained with Webb’s MIRI (Mid-Infrared Instrument), displays a number
of emission lines from water vapor. Scientists determined that the water is in
the system’s inner disk, at distances of less than 100 million miles from the
star, the region where rocky, terrestrial planets may be forming.
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- There are two known planets in this system,
PDS 70b and PDS 70c, both of which are the size of Jupiter. These gas giants
are located within the gap between the two dusty disks, and the “c planet” may
have a moon orbiting it. That other planets have already formed in this system
bodes well for the future formation of other worlds.
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- But the question remains, where did the
water come from? One possibility is
that hydrogen and oxygen atoms are meeting in the region, forming water.
Another possibility is that the water migrates from the cool outer disk into
the inner system.
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- PDS 70 is a K-type star, cooler than our
Sun, and is estimated to be 5.4 million years old. This is relatively old for a
star to have planets still forming, since over time, the gas and dust content
of planet-forming disks declines.
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- Ether the central star’s radiation and
winds blow out such material, or the dust combines and grows into larger
objects over time, which eventually form planets. This late planet formation
also makes the discovery of water vapor surprising.
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August 10, 2023 ROGUE
PLANETS - roaming without a sun? 4115
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