Two new temperate rocky worlds discovered

They are located about 100 light-years from Earth.

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An international research team, including astronomers at the University of Birmingham, reported about the discovery of two new temperate rocky worlds, i.e., “super-Earth” planets orbiting a small, cool star called LP 890-9. The system is located about 100 light-years from Earth.

Also known as TOI-4306 or SPECULOOS-2, the star is the second coolest star found to host planets. LP 890-9b is the system’s inner planet. It is 30% larger than Earth and orbits the star in just 2.7 days.

This first planet was initially identified as a possible planet candidate by NASA’s TESS mission. This candidate was confirmed and characterized by the SPECULOOS telescopes, one of which is operated by the University of Birmingham.

LP 890-9 emits most of their light in the near-infrared and for which TESS has rather limited sensitivity. The telescopes of the SPECULOOS project, installed at ESO’s Paranal Observatory in Chile and on the island of Tenerife, are optimized to observe this type of star with high precision, thanks to cameras that are very sensitive in the near-infrared.

The observations of LP 890-9 made by SPECULOOS were successful since they not only helped confirm the existence of the first planet but also helped identify a second, previously undiscovered planet.

This second planet, LP 890-9c, also known as SPECULOOS-2c, is similar in size to the first (about 40% larger than Earth). It orbits the star in 8.5 days. This orbital period, later confirmed with the MuSCAT3 instrument in Hawaii, places the planet in the so-called “habitable zone” around its star.

Amaury Triaud, a professor of Exoplanetology at the University of Birmingham and the leader of the SPECULOOS working group that scheduled the observations leading to the discovery of the second planet, said“The habitable zone is a concept under which a planet with similar geological and atmospheric conditions as Earth, would have a surface temperature allowing water to remain liquid for billions of years. This gives us a license to observe more and find out whether the planet has an atmosphere, and if so, to study its content and assess its habitability.”

Scientists are further planning to study the atmosphere of this planet using NASA’s Webb, for which LP 890-9c appears to be the second-most favorable target among the potentially habitable terrestrial planets known so far.

Journal Reference

  1. L. Delrez, C.A. Murray, F.J. Pozuelos, N. Narita, E. Ducrot, M. Timmermans, N. Watanabe, A.J. Burgasser, T. Hirano, B.V. Rackham, K.G. Stassun, V. Van Grootel, C. Aganze, M. Cointepas, S. Howell, L. Kaltenegger, P. Niraula, D. Sebastian. Two temperate super-Earths transiting a nearby late-type M dwarf. Astronomy & Astrophysics, 2022; DOI: 10.1051/0004-6361/202244041
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