Astronomers using NASA’s Transiting Exoplanet Survey Satellite (TESS) have discovered a planetary system containing at least three small planets, orbiting an M3V-type star called TOI 270.
An artist’s impression of the TOI 270 planetary system. Image credit: Sci-News.com.
TOI 270, also known as TIC 259377017, 2MASS J04333970-5157222 and L 231-32, is approximately 73 light-years away from Earth.
The star has a magnitude of 8.3 and is roughly 40% the size and mass of our Sun.
The Super-Earth-sized and two sub-Neptune-sized exoplanets transiting TOI-270 were detected by NASA’s TESS mission in 2018, and followed up with ground-based telescopes.
Named TOI-270b, c and d, the planets are between 1.25 and 2.42 times the size of Earth.
They have orbital periods of 3.4, 5.7, and 11.4 days, respectively.
This image, taken by the NaCo (NAOS-CONICA) instrument on ESO’s Very Large Telescope, shows TOI 270. Image credit: Günther et al / ESO.
“The radius of TOI-270b places it in a planetary population distinct from planets TOI-270c and d,” said MIT astronomer Maximilian Günther and co-authors.
“The trio is separated by the planetary radius gap around 1.7-2 Earth radii which divides two populations of planets, rocky super-Earths and gas-dominated sub-Neptunes.”
“TOI-270b likely falls into the regime of Earth-like/rocky compositions, while planets TOI-270c and d likely have rocky/icy compositions.”
“Notably, the surface temperature of TOI-270d (153 degrees Fahrenheit, or 67 degrees Celsius) lies within the survivable range for extremophile organisms.”
The three exoplanets are among the smallest and nearest transiting exoplanets known to date.
“The TOI-270 system shows great potential for accurate characterization and formation studies of small planets near the habitable zone,” the astronomers said.
“It will be a prime target for future studies since: (i) its near-resonance allows the detection of transit timing variations for precise mass measurements and detailed dynamical studies; (ii) its brightness enables independent radial velocity mass measurements; (iii) the outer planets are ideal for atmospheric characterization via transmission spectroscopy with the future James Webb Space Telescope (JWST); and (iv) the quiet host star is well suited for future searches of terrestrial planets within the habitable zone.”
“Altogether, very few systems with temperate small exoplanets are as suitable for complementary characterization by transit timing variations, radial velocities and transmission spectroscopy as TOI-270.”
A paper reporting the discovery was published on arXiv.org.
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Maximilian N. Günther et al. 2019. A Super-Earth and two sub-Neptunes transiting the bright, nearby, and quiet M-dwarf TOI-270. arXiv: 1903.06107
