Using the radial velocity technique, astronomers have discovered a super-Earth exoplanet orbiting near the inner edge of the habitable zone of the cool M-dwarf Ross 508.
“Exoplanets are known to orbit various types of stars such as solar-type stars, low-mass M-dwarfs (red dwarf stars), evolved stars, and stellar remnants,” said Subaru Telescope astronomer Hiroki Harakawa and colleagues.
“Among them, M-type stars are especially promising targets for the detection of Earth-like planets.”
“These stars’ small sizes make transits relatively deep, and their low luminosities make the habitable zone close to the star where the radial velocity amplitude is larger.”
“Nevertheless, exoplanet discoveries around cool M-dwarfs are still limited.”
The newly-discovered exoplanet orbits Ross 508, an M4.5-type dwarf about five times smaller and less massive than the Sun.
Also known as Gliese 585, LTT 14584, LHS 396 and LSPM J1523+1727, the parent star is located 36.5 light-years (11.2 parsecs) away in the constellation of Serpens.
Named Ross 508b, the alien world is approximately 4 times more massive than Earth.
The planet orbits its star once every 10.77 days at a distance of only 0.054 astronomical units (AU).
“This gives an orbit-averaged insolation of 1.4 times the Earth’s value, placing Ross 508b near the inner edge of its star’s habitable zone,” the researchers said.
“Future surveys with IRD and other high-precision NIR spectrographs will enable the discovery of planets around more stars like Ross 508, and will establish the diversity of their planetary systems,” the authors said.
“Exoplanet exploration will be advanced by the other late-M-dwarf radial velocity surveys using high-dispersion spectrographs, such as HPF, CARMENES, and SPIROU, as well as exoplanet surveys using the transit technique from space (e.g., TESS) and the ground (e.g., SPECULOOS).”
“Hence, the findings from various late-M-dwarf observing campaigns in the 2020s will be combined to provide important clues to reveal the true nature of planetary systems around cool M-dwarfs.”
Hiroki Harakawa et al. 2022. A Super-Earth Orbiting Near the Inner Edge of the Habitable Zone around the M4.5-dwarf Ross 508. PASJ, in press; arXiv: 2205.11986