An international team of researchers has discovered a new planet, GJ 367 b, with a surface temperature of up to 1,500 degrees Celsius – hot enough to melt all rock and metal – and which takes just eight hours to orbit around it. his star.
In a new study published in the Science journal, researchers show that the planet, located 31 light years from Earth, is one of the lightest of the nearly 5,000 exoplanets (planets outside our own solar system) known today, with the half the mass of the Earth. It has a diameter of just over 9,000 kilometers – slightly larger than Mars.
The team says the research represents a step forward in the search for a “second Earth” because it shows that astronomers can determine the properties of even very small planets.
Co-author Dr Vincent Van Eylen (UCL Mullard Space Science Laboratory) said: “In this new study, the size and mass of the planet were calculated using two methods, both of which involved d ‘analyze the star light on the planet. One was to measure the tiny drop in light emitted by the star as the planet passed in front of it. This was done using data from NasaSatellite for the study of exoplanets in transit (TRIAL).
“The other method was to deduce the mass of the planet from the effect it had on the movement of the star. This movement was light – at a speed of 80cm per second it was nothing more than a walking speed – so it’s fantastic that we were able to detect this little movement 31 light years away.
The study involved 78 researchers and was led by astronomers from the Institute for Planetary Research of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR).
Lead author Dr Kristine Lam, DLR, said: “Based on the precise determination of its radius and mass, GJ 367b is classified as a rocky planet. This places it among the terrestrial planets smaller than Earth and advances research in the search for a “second Earth”.
GJ 367 b belongs to the group of “ultra-short-lived” (USP) exoplanets that orbit their star in less than 24 hours. “We already know of a few, but their origins are currently unknown,” Dr Lam said. “By measuring the precise fundamental properties of the planet USP, we can gain insight into the history of the system’s formation and evolution. “
Following the discovery of this planet using TESS and the transit method, the spectrum of its star was then studied from the ground using the HARPES instrument on the 3.6 m telescope of the European Southern Observatory.
Through the combination of different evaluation methods, the radius and mass of the planet were determined: its radius is 72% of the radius of the Earth, and its mass is 55% of the mass of the Earth.
By determining its radius and its mass with a precision of 7 and 14 percent respectively, the researchers were also able to draw conclusions about the exoplanetthe internal structure of. It is a rocky planet of low mass, but has a higher density than Earth. “The high density indicates that the planet is dominated by an iron core,” said Dr Szilárd Csizmadia.
“These properties are similar to those of Mercury, with its disproportionate iron and nickel core that sets it apart from other terrestrial bodies in the solar system. “
However, the planet’s proximity to its star means it is exposed to an extremely high level of radiation, more than 500 times stronger than what Earth is experiencing. The surface temperature can reach up to 1500 degrees Celsius – a temperature at which all rocks and metals would be melted.
The mother star of this newly discovered exoplanet, a red dwarf called GJ 367, is only about half the size of the Sun. This was beneficial for its discovery because the transit signal of the orbiting planet is particularly important. Red dwarfs are not only smaller, but also cooler than the Sun. This makes their associated planets easier to find and characterize. They are among the most common stellar objects in our cosmic neighborhood and are therefore suitable targets for research on exoplanets.
Researchers estimate that these red dwarfs, also known as “M-class stars,” orbit on average two to three planets, each of which is no more than four times the size of Earth.
To learn more about this discovery, read The Under-Terrestrial Planet Discovered By Astronomers: New World Boiling is Ultra-light and Ultra-Fast.
Reference: « GJ 367b : A dense ultra-short period sub-Earth planet transiting a near red dwarf star » by Kristine WF Lam, Szilárd Csizmadia, Nicola Astudillo-Defru, Xavier Bonfils, Davide Gandolfi, Sebastiano Padovan, Massimiliano Esposito, Coel Hell , Teruyuki Hirano, John Livingston, Felipe Murgas, Alexis MS Smith, Karen A. Collins, Savita Mathur, Rafael A. Garcia, Steve B. Howell, Nuno C. Santos, Fei Dai, George R. Ricker, Roland Vanderspek, David W Latham, Sara Seager, Joshua N. Winn, Jon M. Jenkins, Simon Albrecht, Jose M. Almenara, Etienne Artigau, Oscar Barragán, François Bouchy, Juan Cabrera, David Charbonneau, Priyanka Chaturvedi, Alexander Chaushev, Jessie L. Christiansen, William D. Cochran, José R. De Meideiros, Xavier Delfosse, Rodrigo F. Díaz, René Doyon, Philipp Eigmüller, Pedro Figueira, Thierry Forveille, Malcolm Fridlund, Guillaume Gaisné, Elisa Goffo, Iskra Georgieva, Sascha Grziwa, Eike Guenther, Hatzes, Marshall C. Johnson, Petr Kabáth, Emil Knudstrup , J udith Korth, Pablo Lewin, Jack J. Lissauer, Christophe Lovis, Rafael Luque, Claudio Melo, Edward H. Morgan, Robert Morris, Michel Mayor, Norio Narita, Hannah LM Osborne, Enric Palle, Francesco Pepe, Carina M. Persson , Samuel N. Quinn, Heike Rauer, Seth Redfield, Joshua E. Schlieder, Damien Ségransan, Luisa M. Serrano, Jeffrey C. Smith, Ján Šubjak, Joseph D. Twicken, Stéphane Udry, Vincent Van Eylen et Michael Vezie, 2 décembre 2021, Science.
DOI : 10.1126/science.aay3253