Glowing hot super-Earth nearby

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Artist’s impression of the surface of the newly discovered hot super-Earth

Artist’s impression of the surface of the newly discovered hot super-Earth Gliese 486b. With a temperature of about 700 Kelvin (430 °C), the team of the CARMENES collaboration expects a Venus-like hot and dry landscape criss-crossed by glowing lava flows. Gliese 486b may have a thin atmosphere. Photo: RenderArea

Research team with Göttingen University participation plans to test atmospheric models of the rocky planet

In the past two and a half decades, astronomers have discovered thousands of exoplanets made of gas, ice and rock. Only a few of them are Earth-like. Studying their atmospheres with the instruments currently available is a major challenge. The CARMENES consortium with participation of the University of Göttingen has now discovered a hot super-Earth orbiting the nearby red dwarf star Gliese 486. Despite its short distance from the parent star, the planet - Gliese 486b - may have retained part of its original atmosphere. This means that it is perfectly suited for research on its atmosphere and interior, both from the ground and in space, using the next generation of telescopes. The results of the research were published .

Planetary atmospheres must fulfil certain criteria to be suitable for observation by the next generation of telescopes. At a distance of only 26 light years, researchers led by the Max Planck Institute for Astronomy in Heidelberg have now found a planet orbiting the red dwarf star Gliese 486 that perfectly meets the requirements for rocky planets. The newly discovered planet is a super-Earth with a mass 2.8 times that of our home planet. It is also 30 per cent larger than Earth. "The proximity of this exoplanet is exciting because we can study it more closely with powerful telescopes such as the James Webb Space Telescope in the near future, and the different Extremely Large Telescopes," explains lead author Dr Trifon Trifonov from the Max Planck Institute for Astronomy. Calculating the mean density of the planet from the determined masses and radii shows that it has a similar composition to Venus and Earth, including a metallic core. Anyone standing on Gliese 486b would feel a gravitational pull 70 per cent stronger than the one we experience on our own world.

Gliese 486b orbits its dwarf star on a circular path in less than 1.5 days and at a distance of 2.5 million kilometres. A rotation around its own axis takes the same amount of time, so that one side is always facing the star. Although the star Gliese 486 is much fainter and cooler than the Sun, the radiation is so intense that the planet’s surface heats up to at least 700 Kelvin, or about 430 degrees Celsius. In this sense, the surface of Gliese 486b probably resembles Venus more than Earth, with a hot and arid landscape criss-crossed by glowing lava flows. Unlike Venus, however, Gliese 486b may have only a thin atmosphere, if any. Model calculations could be consistent with both scenarios, as stellar irradiation can cause atmospheres to evaporate. At the same time, the planet’s gravity helps to maintain it.

The CARMENES project (Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs) has been observing more than 300 stars to detect their planets regularly since 2016. The scientific leadership of the consortium is shared between the Institute for Astrophysics at the University of Göttingen and the Institut de Cičncies de l’Espai in Barcelona. "All CARMENES data are processed at the Institute of Astrophysics and analysed using software developed at our institute," says co-author Professor Ansgar Reiners. Since 2017, the German Research Foundation (DFG) has funded a research group for the scientific analysis of the CARMENES data, whose lead is the Göttingen Institute for Astrophysics.

Original publication: T. Trifonov, J. A. Caballero, J. C. Morales et al. A nearby transiting rocky exoplanet that is suitable for atmospheric investigation. Science (2021). Doi: 10.1126/science.abd7645

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