Two Earth-mass exoplanets orbiting a discovered star

Two Earth-mass exoplanets orbiting a discovered star

Planetary signals. Upper left panel: RV of the folded GJ 1002 b phase with a period of 10.35 days, after subtracting the activity pattern and the signal at 20.2 days. Upper right panel: RV of the folded GJ 1002 b phase with a period of 20.2 days, after subtracting the activity pattern and the signal at 10.335 days. Bottom panels: Corresponding phase bent residues. Credit: Mascareño et al, 2022

Using the radial velocity (RV) method, an international team of astronomers has discovered two new exoplanets transiting a nearby M dwarf star known as GJ 1002. The new alien worlds have masses similar to our own. planet and orbit around the host star in its habitable zone. The discovery is reported in an article published in Astronomy & 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 as it orbits around the star. Thanks to this technique, more than 600 exoplanets have been detected to date.

Now a group of astronomers led by Alejandro Suárez Mascareño of the University of La Laguna, Spain, reports the discovery of two new extrasolar planets following RV measurements of the M dwarf GJ 1002. The observations that led to the discovery were conducted with the SPectrograph Echelle for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) and the Calar Alto High-Resolution Research for M dwarfs with Exoterres with Near Infrared and Optical Scale Spectrographs (CARMENES).

“We studied the neighboring M dwarf GJ 1002 using RV and activity indicators from ESPRESSO and CARMENES. Using a joint model combining information from the FWHM [full-width half maximum] of the CCF [cross-correlation function] and RV in a multi-series 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. They both orbit GJ 1002 in its habitable zone and since the star is only 15.78 Light years away, the planets are some of the closest to Earth that could potentially host habitable environments.

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

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

The parent star GJ 1002 is a weak 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 star’s effective temperature is 3024 K and its metallicity has been measured at around -0.25.

The researchers noted that it is possible that there are other Earth-mass planets in the outer half of GJ 1002. living area.

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

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

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