Astronomers discover a ‘super Earth’ orbiting an M dwarf star

An international team of astronomers reports the discovery of a new “super-Earth” exoplanet with NASA’s Transiting Exoplanet Survey Satellite (TESS). The newly discovered alien world, dubbed TOI-1680 b, is about 50% larger than Earth and orbits an M dwarf star located about 120 light-years away. The finding was detailed in a paper published July 11 on the arXiv preprint server.

TESS is conducting a survey of some 200,000 of the brightest stars near the sun with the aim of looking for transiting exoplanets. So far, it has identified nearly 6,700 candidate exoplanets (TESS OBJECTS OF INTEREST, or TOIs), of which 363 have been confirmed so far.

In a recent research paper, a group of astronomers led by Mourad Ghachoui of the University of Liege, Belgium, confirmed another TOI monitored by TESS. Ghachoui and his colleagues report that a transit signal was identified in the light curve of an inactive M dwarf known as TOI-1680. The planetary nature of this signal was confirmed by ground-based tracking photometry, high-resolution imaging, and spectroscopic observations.

“We have reported the discovery and initial characterization of TOI-1680 b, a super-Earth orbiting a faint medium M dwarf (V = 15.87),” the researchers wrote in the paper.

TOI-1680 b has a radius of 1.46 Earth radii and a predicted mass of about 3.18 Earth masses, giving an average density of 5.5 g/cm3. The planet orbits the host star every 4.8 days, at a distance of about 0.03 AU from it. The equilibrium temperature of TOI-1680 b is estimated to be 404 K.

The parent star TOI-1680 (also known as TIC 259168516) is a faint, inactive star of spectral type M4.5. It is about five times smaller and less massive than the sun. The distance to TOI-1680 was calculated to be 121 light years and the effective temperature of the star was found to be about 3211 K.

The study found that TOI-1680 b has a transmission spectroscopic metric (TSM) at a level of 7.82. This result suggests that TOI-1680 b could be a suitable target for atmospheric characterization studies with the NIRSpec/PRISM instrument aboard the James Webb Space Telescope (JWST).

“According to the transmission spectroscopy metric (TSM) of Kempton et al. (2018), TOI-1680 b could be a promising candidate for atmospheric characterization with the JWST… Specifically, among 63 targets, TOI-1680 b ranks as the 13th most suitable target for these studies,” the paper authors noted.

In addition to atmospheric characterization studies, Ghachoui’s team proposes measurements of the radial velocity of TOI-1680 b with the high-resolution fiber-optic powered echelle spectrograph MAROON-X on the 8.1-m Gemini North telescope. Such research should provide a direct mass measurement, which will be crucial in determining the composition of this planet.