Two Earth-mass exoplanets have been discovered orbiting a nearby star

Planetary signs. Upper left panel: GJ 1002 b instar RVs folded at 10.35 days, after subtracting the activity and signal model at 20.2 days. Upper right panel: GJ 1002 b instar RVs folded at 20.2 days, after subtracting the activity and signal model at 10.335 days. Lower panels: remnants of the corresponding folded phase. Credit: Mascareño et al, 2022

Using the radial velocity (RV) method, an international team of astronomers has discovered two new exoplanets passing through a nearby M dwarf star known as GJ 1002. The recently discovered alien worlds have similar masses to our planet and orbit the host star in its location. habitable area. The results have been reported in a paper published in Astronomy and astrophysics.

The radial velocity (RV) method for exoplanet detection relies on detecting variations in the velocity of the central star, due to the changing direction of the gravitational pull of an unseen exoplanet as it orbits the star. Thanks to this technology, more than 600 exoplanets have been discovered so far.

Now, a group of astronomers led by Alejandro Suárez Mascareño of the University of Laguna, Spain is reporting the discovery of two new exoplanets as a result of RV measurements of M-dwarf GJ 1002. The observations that led to the discovery were made using the Echelle Spectrograph for rocky exoplanets and spectroscopic observations. The sedentary (ESPRESSO) and Calar Alto high-resolution search for M dwarfs with Exoarts with near-infrared and Echelle Spectrographs (CARMENES).

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

The newly discovered exoplanets received the designations GJ 1002 b and GJ 1002 c. Both orbit GJ 1002 within its habitable zone, and given that the star is only 15.78 light-years away, the planets are some of the closest to Earth that could host habitable environments.

According to the paper, GJ 1002 b has a minimum mass of about 1.08 Earth masses. It orbits its parent star every 10.35 days, at a distance of about 0.0457 AU from it. The planet’s equilibrium temperature has been estimated to be 230.9 K.

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

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 a mass of about 0.12 solar masses. The star’s effective temperature is 3,024 K and its metallicity has been measured at about -0.25.

The researchers indicate that additional Earth-mass planets may exist in the outer half of GJ 1002’s habitable zone.

Gaia DR3 [Data Release 3] The data indicates an excess of astronomical noise that could indicate a massive companion at large orbital separation.”

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

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