Classifying exoplanet atmospheres opens new field of study
Date:
April 26, 2022
Source:
National Institutes of Natural Sciences
Summary:
An international team of researchers examined data for 25 exoplanets
and found some links among the properties of the atmospheres,
including the thermal profiles and chemical abundances in
them. These findings will help establish a generalized theory
of planet formation which will improve our understanding of all
planets, including the Earth.
FULL STORY ==========================================================================
An international team of researchers examined data for 25 exoplanets and
found some links among the properties of the atmospheres, including the
thermal profiles and chemical abundances in them. This marks the first
time exoplanet atmospheres have been studied as populations, rather than individually. These findings will help establish a generalized theory
of planet formation which will improve our understanding of all planets, including the Earth.
========================================================================== Today there are more than 3000 confirmed exoplanets, planets orbiting
stars other than the Sun. Because they are far away from Earth, it is
difficult to study them in detail. Determining the characteristics of
even one exoplanet has been a noteworthy accomplishment.
In this research, astronomers used archival data for 25 hot Jupiters,
gas giant planets that orbit close to their host stars. The data included
600 hours of observations from the Hubble Space Telescope and more than
400 hours of observations from the Spitzer Space Telescope.
One of the characteristics investigated by the team was the presence
or absence of a "thermal inversion." Planetary atmospheres trap heat,
so in general the temperature increases as you probe deeper into the atmosphere. But some planets show a thermal inversion where an upper
layer of the atmosphere is warmer than the layer beneath it. On Earth,
the presence of ozone causes a thermal inversion. The team found that
almost all of the hot Jupiters with a thermal inversion also showed
evidence for hydrogen anion (H-) and metallic species such as titanium
oxide (TiO), vanadium oxide (VO), or iron hydride (FeH).
Conversely, exoplanets without these chemicals almost never had thermal inversions. It is difficult to draw conclusions based on correlation
alone, but since these metallic species are efficient absorbers of
stellar light, one theory holds that when these chemicals are present
in the upper atmosphere, they absorb light from the host star and cause
the temperature to increase.
Masahiro Ikoma at the National Astronomical Observatory of Japan, a co- investigator in this study, explains, "The theory of gas giant formation proposed by my students and I predicted diversity in the composition
of hot Jupiter atmospheres, and helped to motivate this systematic
survey of atmospheric characteristics." This new study, identifying populations of similar exoplanet atmospheres, will help refine the
theoretical models, bringing us closer to a comprehensive understanding
of planet formation. In the coming decade, new data from next- generation
space telescopes, including the James Webb Space Telescope, Twinkle,
and Ariel, will provide data for thousands of exoplanets, both enabling
and necessitating new categories for classifying exoplanets beyond the
methods explored in this research.
========================================================================== Story Source: Materials provided by
National_Institutes_of_Natural_Sciences. Note: Content may be edited
for style and length.
========================================================================== Journal Reference:
1. Q. Changeat, B. Edwards, A. F. Al-Refaie, A. Tsiaras, J. W. Skinner,
J.
Y. K. Cho, K. H. Yip, L. Anisman, M. Ikoma, M. F. Bieger,
O. Venot, S.
Shibata, I. P. Waldmann, G. Tinetti. Five Key Exoplanet Questions
Answered via the Analysis of 25 Hot-Jupiter Atmospheres in
Eclipse. The Astrophysical Journal Supplement Series, 2022; 260
(1): 3 DOI: 10.3847/ 1538-4365/ac5cc2 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/04/220426101752.htm
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