Clouds make climate modeling on Earth challenging.
Identifying, and perhaps defining atmospheric phenomena on distant planets is the next big
exoplanet problem.
Scientists have discovered clouds on a gas giant exoplanet 520 light-years from Earth
using data from numerous telescopes.
The observations were so detailed that they were able to determine the altitude of the
clouds and the structure of the upper atmosphere with unprecedented precision.
Continued research will help us better comprehend exoplanet atmospheres and search for worlds
with potentially habitable circumstances or biosignatures in their spectra.
The exoplanet in question is WASP-127b, which was discovered in 2016.
It is a hot, puffy beast that orbits its star so close that its year is only 4.2 days long.
The exoplanet is 1.3 times the size of Jupiter, but only 0.16 times the mass of Jupiter, making
it one of the least dense or fluffiest exoplanets ever discovered.
Dr. Romain Allart's presentation at the Europlanet Science Congress (EPSC) 2021 demonstrates
how he and his team were able to expose the upper structure of the planet's atmosphere
by integrating data from a spacecraft and a ground-based observatory.
This opens the door to similar research into a variety of other distant worlds.
To gaze into different altitudes of WASP-127b's atmosphere, they used infrared data from the
Hubble Space Telescope and optical data from the ESPRESSO instrument on the ground-based
Very Large Telescope at the European Southern Observatory's Very Large Telescope in Chile.
First, they identified the presence of sodium, as they had seen before on this type of planet,
but at a considerably lower altitude than they had expected.
Second, there were substantial infrared water vapor signals but none at visible wavelengths.
This means that clouds that are opaque at visible wavelengths but transparent in the
infrared are screening water vapor at lower levels.
The researchers were able to narrow down the altitude of the clouds to a surprisingly low
cloud layer with a pressure ranging between 0.3 and 0.5 millibars using the combined data
from the two instruments.
The clouds' composition is not yet known, excluding that they are not made up of water
droplets like they are on Earth.
It's also a puzzle why sodium is found in such an unusual place on this planet.
It's challenging to figure out the makeup of exoplanetary atmospheres.
Because we can't observe most exoplanets directly, we have to infer their presence based on their
effects on their host stars.
One of these is dimming and brightening: when an exoplanet passes between us and a star,
the star's light dims slightly.
Future research will help scientists learn more about the atmosphere and WASP-127b generally,
which is proving to be an intriguing place.
WASP-127b receives 600 times more irradiation than the Earth and encounters temperatures
of up to 1100 degrees Celsius throughout its four-day orbit around its star.
This expands the planet's radius to 1.3 times that of Jupiter, but with barely a fifth of
Jupiter's mass, making it one of the least dense or fluffiest exoplanets yet identified.
Fluffy exoplanets are easier to observe due to their stretched nature, making WASP-127b
a perfect option for scientists working on the characterization of the atmosphere.
According to the team's observations, WASP-127b orbits its host star in an unusual way.
All planets in the solar system orbit in the direction of the Sun's rotation, in a more-or-less
flat plane around the Sun's equator.
This is due to the solar system's formation, which began with a disc of material swirling
into the spinning Sun.
WASP-127b not only orbits in the opposite direction of its star's rotation, but it also
orbits its star at an extremely prominent angle, almost around the star's poles.
The system is estimated to be roughly 10 billion years old, implying that something unusual
is happening in that particular vicinity.
“Such alignment is unexpected for a hot Saturn in an old stellar system and might
be caused by an unknown companion,” Allart said.
“All these unique characteristics make WASP-127b a planet that will be very intensely studied
in the future.”
Hopefully, more research will be carried out to find out about its atmosphere and unique
features.
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