A super-Earth planet has been discovered near the habitable zone of a red dwarf star only 37 light-years from the Earth.
The new discovery of a super-Earth is the first breakthrough by a new instrument on the Subaru Telescope. It offers a chance to investigate the possibility of life on planets located by nearby stars. With such a successful first result, expectations are that the Subaru Telescope will discover more, potentially even better, candidates for habitable planets around red dwarfs.
Analysing red dwarfs
Red dwarfs – stars that are smaller than the Sun – account for three-quarters of the stars in the Milky Way and are abundant in the neighbourhood around the Sun. As such, they are important targets in the searching nearby extra-solar planets and extra-terrestrial life. However, red dwarfs are cool and do not emit much visible light compared to other types of stars, making it difficult to study them.
In infrared wavelengths, red dwarfs are brighter. As a result, the Astrobiology Centre in Japan developed an infrared observational instrument mounted on the Subaru Telescope to search for signs of planets around red dwarf stars. The instrument is called IRD for Infrared Doppler, the observational method used in this search.
Schematic diagram of the newly discovered Ross 508 planetary system. The green region represents the habitable zone where liquid water can exist on the planetary surface. The planetary orbit is shown as a blue line. Ross 508 b skims the inner edge of the habitable zone (solid line), possibly crossing into the habitable zone for part of the orbit (dashed line). Credit: Astrobiology Center
The Subaru Telescope: locating a super-Earth
The first fruits of this search are signs of a super-Earth four times the mass of the Earth circling the star Ross 508, located 37 light-years away in the constellation Serpens. This planet, Ross 508 b, has a year of only 11 Earth-days and lies at the inner edge of the habitable zone around its host star.
Interestingly, there are indications that the orbit is elliptical, which would mean that for part of the orbit, the planet would be in the habitable zone. In this region, conditions would be right for liquid water to exist on the surface of the planet. Whether or not there is water or life present are questions for further studies.
Ross 508 b planet
To have the very first planet discovered by this new method be so tantalisingly close to the habitable zone seems too good to be true and bodes well for future discoveries. Bun’ei Sato, a Professor at the Tokyo Institute of Technology and the Principal Investigator in this search concluded: “It has been 14 years since the start of IRD’s development. We have continued our development and research with the hope of finding a planet exactly like Ross 508 b.”
These results appeared as Harakawa et al. ‘A Super-Earth Orbiting Near the Inner Edge of the Habitable Zone around the M4.5-dwarf Ross 508’ in Publication of the Astronomical Society of Japan on 30 June 2022.
