An analysis of hundreds of hours of observations by the Hubble Space Telescope has revealed what makes some exoplanets incredibly hot.
In a new study, a team of scientists analyzed the atmospheres of 25 hot Jupiters, Jupiter-sized exoplanets. These planets, however, orbit extremely close to their parent stars, even closer than Mercury orbits towards the sun, making them extremely hot. This new study suggests that the atmospheres of these exoplanets exhibit some unusual thermal behavior that could be related to the chemical composition of the planets.
Using over 600 hours of observations by Hubble Space Telescope and 400 hours of observations by now retired from NASA Spitzer Space Telescope, the study found that some of the atmospheres of the hot Jupiters studied contain high concentrations of hydrogen, titanium oxide, vanadium oxide, and iron hydride. These atmospheres exhibited what scientists call a thermal inversion, a phenomenon whereby atmospheric temperature increases rather than decreases with altitude. (Under normal circumstances, the temperature of an atmosphere is highest near the surface and decreases with altitudes as the density of the atmosphere decreases.)
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In the Hubble data, the atmospheres of these exoplanets were also, on average, warmer than those without these chemical compounds, reaching temperatures of 1,726 degrees Celsius. Scientists believe there may be a direct link. The hydrogen, titanium oxide, vanadium oxide and iron hydride in the planet’s atmosphere could act as light absorbers, blocking heat from the nearby star, they think.
The researchers suggested in the study that some sort of feedback loop might be happening on these planets. Warm temperatures keep light-absorbing compounds stable in these atmospheres, which in turn causes the atmospheres to absorb more starlight and heat up even more, especially in the upper layers.
the scientists said in a statement that of the 25 hot Jupiters studied, those colder than 3,140 degrees F showed neither the presence of the compounds nor thermal inversion.
The study is one of the first to analyze an entire population of exoplanets rather than isolated cases.
“The amount of information we learn about chemistry and the formation [of the exoplanets] – thanks to a decade of intense observation campaigns – is incredible,” said Quentin Changeat, an astrophysicist at University College London and lead author of the study. in the declaration.
The analysis could help predict the behavior of other exoplanets in the future and unravel processes related to planet formation, the scientists said.
The study was published April 25 in The Astrophysical Journal.