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Classification of the atmosphere of exoplanets opens up a new field of study

Classification of the atmosphere of exoplanets opens up a new field of study

An international team of researchers examined data on 25 exoplanets and found links between atmospheric properties, including thermal features and the chemical abundance they contain. This is the first time that the atmospheres of exoplanets have been studied as groups rather than individually. These discoveries will help create a general theory of planetary formation that will improve our understanding of all planets, including Earth.

Today there are more than 3,000 confirmed exoplanets, which are planets orbiting stars other than the Sun. Because it is far from Earth, it is difficult to study it in detail. Determining the characteristics of a single exoplanet was a remarkable feat.

In this research, astronomers used archival data for 25 hot Jupiters, gas giants that orbit near their host stars. The data included 600 hours of Hubble Space Telescope observations and more than 400 hours of Spitzer Space Telescope observations.

One of the properties the team studied is the presence or absence of a “thermal reflection”. The atmospheres of planets trap heat, so the temperature generally increases as you go deeper into the atmosphere. But some planets show a thermal reversal in which the upper layer of the atmosphere is much hotter than the layer below it. On Earth, the presence of ozone causes a thermal reversal. The team found that nearly all hot Jupiters with thermal reversal also showed evidence of hydrogen anion (H) and metal species such as titanium oxide (TiO), vanadium oxide (VO) or iron hydride (FeH). Conversely, exoplanets without these chemicals have never experienced inversions. It’s hard to draw conclusions based on correlation alone, but because these mineral species absorb starlight efficiently, one theory is that when these chemicals are in the upper atmosphere, they absorb starlight and cause an increase in temperature. .

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Masahiro Ikuma of the National Astronomical Observatory of Japan, a co-author of this study, explains: “The theory of formation of gas giants proposed by my students and I predicted diversity in the composition of Jupiter’s hot atmosphere, and it helped stimulate this systematic investigation of atmospheric properties.”

This new study, which identifies groups of similar atmospheres of exoplanets, will help improve theoretical models, and bring us closer to a comprehensive understanding of planetary formation. Over the next decade, new data from next-generation space telescopes, including the James Webb Space Telescope, Twinkle and Ariel, will provide data for thousands of exoplanets, enabling and requiring new classes for classifying exoplanets outside the scope of the methods explored in this research. .

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Materials offered by National Institutes of Natural Sciences. Note: Content can be modified according to style and length.