Astronomers have discovered and validated two small exoplanets orbiting the nearby red dwarf star TOI-1266.
An artist’s impression of the TOI-1266 planetary system. Image credit: Sci-News.com.
TOI-1266, also known as TIC 467179528 and 2MASS J13115955+6550017, is an M2-type dwarf star approximately 118 light-years away in the constellation of Draco.
The star has less than half the mass and size of the Sun and is almost 8 billion years old.
It hosts at least two planets, TOI-1266b and c, which are much closer to the star than our planet is to the Sun.
The inner planet is 2.46 times bigger than Earth and belongs to a class of exoplanets called mini-Neptunes.
It orbits TOI-1266 once every 10.9 days at a distance of only 0.07 AU (astronomical units).
The outer planet has an orbital period of 18.8 days and is 0.1 AU from the star.
The alien world is 1.67 times the size of Earth and resides in the Fulton gap (also known as the radius valley), the transition region between rocky planets and gas giants.
“If TOI-1266c has a rocky composition, it could potentially be a super-Venus,” said Princeton University astronomer Gudmundur Stefansson and colleagues.
TOI-1266b and c receive 4.7 and 2.4 times more sunlight than Earth does from the Sun, respectively.
Both planets are in the so-called Venus-zone, a range of stellar distances where a planet with an initial Earth-like atmosphere could experience a runaway greenhouse effect that transforms it into a Venus-like atmosphere.
“The detailed characterization of systems in the Venus-zone, including mass and atmospheric compositions, will increase our understanding of the limits of habitable environments,” the astronomers said.
Dr. Stefansson and co-authors detected TOI-1266b and c using NASA’s Transiting Exoplanet Survey Satellite (TESS).
They then observed transits of the planets using the 0.43-m Richard S. Perkin telescope at Hobart and William Smith Colleges and the ARCTIC Imager on the 3.5-m ARC telescope at Apache Point Observatory.
They also obtained and analyzed high-resolution spectra of TOI-1266 with the Habitable-Zone Planet Finder to place upper limits on the masses of both planets and to obtain precise parameters of the star.
“We obtained an upper mass limit of 15.9 and 6.4 Earth masses at 95% confidence for planets TOI-1266b and c, respectively,” the researchers said.
“Our current mass constraints hint that TOI-1266c could have a predominantly non-rocky composition, which could indicate that the planet is either water-rich and/or could have retained an atmosphere despite its small size.”
A paper reporting this discovery will be published in one of the AAS journals and is available online.
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Gudmundur Stefansson et al. 2020. A Mini-Neptune and a Venus-Zone Planet in the Radius Valley Orbiting the Nearby M2-dwarf TOI-1266: Validation with the Habitable-zone Planet Finder. AAS journals, in press; arXiv: 2006.11180
