The sun’s impact on the heating of four newly discovered exoplanets

The Leibniz Institute for Astrophysics Potsdam (AIP) conducted a study on the star V1298 Tau and its four orbiting exoplanets. The findings reveal that these newly formed planets are being exposed to intense X-ray radiation from their young sun, causing the vaporization of their atmospheres. In fact, the innermost planets may have lost their atmospheres completely, leaving only their rocky cores behind.

Prompt 1: The AIP astronomers decided to investigate the long-term effects of the star’s influence on the exoplanets. They focused on the recently discovered four-planet system revolving around the young sun V1298 Tau. Although this star is similar in size to our own sun, it is significantly younger, being only 25 million years old compared to our sun’s 4.6 billion years. The system consists of two smaller planets, similar in size to Neptune, in close orbits, and two larger Saturn-sized planets in more distant orbits. To assess the impact of X-ray radiation on the planetary atmospheres, the researchers analyzed the star’s X-ray spectrum using the Chandra space telescope. Based on their observations, they determined the potential outcomes for the four exoplanets.

As the star-planet system ages, the star’s rotation gradually slows down, resulting in a decrease in its magnetism and X-ray emission. According to Laura Ketzer, a Ph.D. student and co-author, the rate at which the star spins down over the next billion years will determine the evaporation of the exoplanets. A faster spin-down would lead to less atmosphere loss. Ketzer has developed a code that can calculate the evolution of the planets over time and has found that the two innermost planets may lose their gas atmospheres completely and become rocky cores if the star spins down slowly. However, the outermost planet will remain a gas giant.

The fate of the third planet depends on its weight, which is currently unknown. Matthias Mallonn, another co-author, has updated the transit properties of the system using observations from AIP’s ground-based STELLA telescope. Katja Poppenhäger concludes that X-ray observations of stars with planets are crucial for understanding the long-term evolution of exoplanetary atmospheres. She expresses excitement about the possibilities that will arise from X-ray observations with eROSITA in the coming years. The eROSITA X-ray telescope, developed in part by AIP, is conducting comprehensive observations of the entire sky and will provide valuable X-ray data for hundreds of exoplanet host stars.

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