An international team of astronomers using NASA’s Transiting Exoplanet Survey Satellite (TESS) has discovered a new exoplanet orbiting a distant star. The newly discovered alien world, called TOI-1420 b, has an extraordinarily low density. The finding was reported in an article published on the preprint server on September 18. arXiv.

TESS surveys some 200,000 of the brightest stars near the Sun in search of transiting exoplanets. Approximately 6,800 candidate exoplanets (TESS Objects of Interest, or TOIs) have been detected so far, of which 385 have been confirmed.

Now, a team of astronomers led by Stephanie Yoshida of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts, reports confirmation of another planet observed by TESS. The team detected a transition signal in the light curve of the late G dwarf star TOI-1420, located approximately 658 light-years away. The planetary nature of this signal was confirmed by subsequent observations using various telescopes.

“We confirm that TOI-1420b is an extremely low-density planet orbiting the last G dwarf in 6.96 days,” the researchers wrote in the paper.

TOI-1420 b has a radius of about 11.89 Earth radii and a mass of about 25.1 Earth masses, giving it an ultra-low density of only 0.082 g/cm.³. The planet orbits at a distance of 0.07 AU from the host and has an equilibrium temperature of approximately 957 K.

Astronomers emphasized that TOI-1420 b is the largest known planet with a mass of less than 50 Earth masses. The planet’s low density suggests that it contains a significant envelope of hydrogen and helium. Using planetary structure models, the researchers calculated that TOI-1420 b has a large envelope mass ratio of about 0.82, meaning its core mass is 4.0 Earth masses.

Looking at TOI-1420’s parent star, it appears to be comparable to the Sun in size and mass. The effective temperature of the star is about 5510 K and its metallicity is 0.28. There is no clear limit to the age of TOI-1420, but the authors of the article suggest that the age of the star does not exceed 10.7 billion years.

In summary, the scientists noted that low-density planets such as TOI-1420 b are excellent targets for future atmospheric characterization and dynamic studies because they are more susceptible to outflows compared to high-gravity planets.

“Overall, TOI-1420 b opens up a number of exciting future prospects in terms of atmospheric and dynamic performance. Comparative planetology of TOI-1420 b, WASP-107 b and other similar low-density worlds will ultimately help unravel their formation and evolution histories.” “, the researchers concluded. Source