Two Earth-mass exoplanets discovered orbiting a nearby star

Two Earth-mass exoplanets discovered orbiting a nearby star

planetary signs. Upper left panel: GJ 1002 phase b folded RVs with a period of 10.35 days, after subtracting the activity model and the signal at 20.2 days. Upper right panel: RVs of GJ 1002 phase b folded with a period of 20.2 days, after subtracting the activity model and the signal at 10.335 days. Lower panels: Folded residues of the corresponding phase. Credit: Mascareño et al, 2022

Using the radial velocity (RV) method, an international team of astronomers discovered two new exoplanets transiting a nearby M dwarf star known as GJ 1002. The newly discovered alien worlds have masses similar to our planet and orbit the host star in your habitable zone. The finding is reported in an article published in Astronomy and Astrophysics.

The radial velocity (RV) method for detecting an exoplanet is based on detecting variations in the velocity of the central star, due to the change in direction of the gravitational pull of an unseen exoplanet while it orbits the star. Thanks to this technique, more than 600 exoplanets have been detected so far.

Now, a group of astronomers led by Alejandro Suárez Mascareño from the University of La Laguna, Spain, reports the discovery of two new extrasolar planets as a result of RV measurements of the M dwarf GJ 1002. Observations leading to the discovery were made with the Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) and the Calar Alto high-resolution search for M dwarfs with Exo-Earths. with Near Infrared and Optical Échelle Spectrographs (CARMENES).

“We studied the nearby M-dwarf GJ 1002 using RVs and activity indicators from ESPRESSO and CARMENES. Using a conjoint model that combined information from the FWHM [full-width half maximum] of the CCF [cross-correlation function] and RVs in a multi-run Gaussian process, we detected the presence of two planetary signals,” the researchers explained.

The newly discovered exoplanets were given the designations GJ 1002 b and GJ 1002 c. Both orbit GJ 1002 within its habitable zone and since the star is only 15.78 Light years away, the planets are among the closest to Earth that could host habitable environments.

According to the paper, GJ 1002 b has a minimum mass of around 1.08 Earth masses. orbits his mother star every 10.35 days, at a distance of about 0.0457 AU from it. The equilibrium temperature of the planet was estimated to be 230.9 K.

GJ 1002 c appears to be slightly more massive than GJ 1002 b, as its minimum mass was calculated to be 1.36 Earth masses. The exoplanet it is separated from the host by about 0.074 AU and its orbital period was measured to be 21.2 days. The equilibrium temperature of GJ 1002 c is at a level of 181.7 K. The astronomers added that this strange world may be a good candidate for further atmospheric characterization.

The parent star GJ 1002 is a faint M dwarf of spectral type M5.5V. It has a radius of about 0.137 solar radii and its mass is about 0.12 solar masses. The effective temperature of the star is 3,024 K and its metallicity was measured to be around -0.25.

The researchers noted that there may be additional Earth-mass planets in the outer half of GJ 1002. habitable zone.

“The Gaia DR3 [Data Release 3] the data show excess astrometric noise that could point to a massive companion with a large orbital separation,” the paper’s authors concluded.

More information:
A. Suárez Mascareño et al, Two Earth-mass temperate planets orbiting the nearby star GJ 1002, Astronomy and Astrophysics (2022). DOI: 10.1051/0004-6361/202244991

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