Two new rocky planets found in the solar neighborhood

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Two new rocky planets found in the solar neighborhood

An international collaboration, involving the Stellar Astrophysics group of the Complutense University, has discovered two new super-Earths orbiting a bright red dwarf star located only 33 light-years away, making them the closest rocky planets ever found outside our solar system.

Neither of the two worlds can harbor life. The temperature of planet b, the closest to the star, is estimated at 435 °C, and planet c, at 284 °C.

Two new exoplanets, HD 260655 b and HD 260655 c, have been detected with the help of NASA’sTransiting Exoplanet Survey Satellite (TESS) space telescope, designed to search for planets orbiting nearby bright stars using the transit method. This method measures the decrease in a star’s brightness when the planet crosses the stellar disk as seen from the telescope.

Research has determined that both planets are "super-Earths," i.e., planets like our own, but larger. Planet b is approximately 1.2 times larger than Earth and planet c 1.5 times. In this case, however, it is unlikely that either world could harbor life. The temperature of planet b, the closest planet to the star, is estimated at 435 °C, and planet c at 284 °C.

At 33 light-years, the discovered exoplanets are relatively close to us, in what is called the solar neighborhood, and their red dwarf star, although smaller than the Sun, is one of the brightest of its kind. This makes the two sister planets prime candidates for atmospheric research.

According to the research, planet b is among the top 10 candidates for atmospheric characterization among all terrestrial exoplanets discovered so far; planet c’is among the top five. "They are in the same category as one of the most famous planetary systems: the seven Earth-sized planets surrounding a star TRAPPIST-1."

These and other rocky exoplanets are already on the observation target list of the James Webb Space Telescope (JWST), which will soon deliver its first scientific images. This telescope will be able to capture data from starlight shining through the atmospheres of these planets. Such light can spread out in a spectrum and reveal the fingerprints of molecules within the atmosphere itself, and can detect water, carbon and other components essential for life.

In addition to the observations made by TESS, scientists have also used data from other ground-based telescopes using the HIRES (Keck telescope, Mauna Kea) and CARMENES (3.5 m telescope, Calar Alto, Almeria) spectrographs to confirm the existence of the two new planets. These telescopes measured the "wobble" of the star, caused by the gravitational tugs of the orbiting planets, which yields information about the mass of the planets. Combining these measurements, it has been possible to determine the density and confirm that they are rocky worlds.

Although it is not yet known whether either of the two super-Earths has an atmosphere and, if so, what it is composed of, the combined data from the various observational studies suggest that the planets do not have distended hydrogen atmospheres.

The international team of astronomers is led by Rafael Luque, a researcher at the Instituto de Astrofísica de Andalucía (IAA-CSIC) and the University of Chicago, with the participation of the Stellar Astrophysics group of the Universidad Complutense led by researcher David Montes have used TESS to make this discovery. The article has been accepted for publication in the scientific journal "Astronomy & Astrophysics" and the results have been presented at the AAS (American Astronomical Society) meeting in Pasadena on June 15, 2022.

Article: Luque, R. et al: "The HD 260655 system: Two rocky worlds transiting a bright M dwarf at 10 pc", Astronomy & Astrophysic, 2022, ArXiv: arXiv:2204.10261


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