• Classifying exoplanet atmospheres opens

    From ScienceDaily@1:317/3 to All on Tue Apr 26 22:30:44 2022
    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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