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NASA's Transiting Exoplanet Survey Satellite (TESS) has found a star, known as "TESS Object of Interest 270," or TOI 270, 73 light-years away from Earth that has three exoplanets orbiting it, including a so-called "super-Earth" and two others that are described as Neptune-like.
“This system is exactly what TESS was designed to find — small, temperate planets that pass, or transit, in front of an inactive host star, one lacking excessive stellar activity, such as flares,” said the study's lead author, Maximilian Günther, in a statement on NASA's website. “This star is quiet and very close to us, and therefore much brighter than the host stars of comparable systems. With extended follow-up observations, we’ll soon be able to determine the make-up of these worlds, establish if atmospheres are present and what gases they contain, and more.”
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Of particular interest is the smaller planet, TOI 270 b, as it is particularly close to the star and only slightly larger than our Earth. Described as an "oven-hot world" by NASA, TOI 270 b orbits the star every 3.4 days, is roughly 25 percent larger than Earth and is estimated to have a mass around 1.9 times greater than Earth’s.
“We’ve found very few planets like this in the habitable zone, and many fewer around a quiet star, so this is rare,” said Stephen Kane, a UC Riverside associate professor of planetary astrophysics, in a separate statement. “We don’t have a planet quite like this in our solar system.”
The other two planets, TOI 270 c and TOI 270 d, are described by NASA as "mini-Neptunes, a type of planet not seen in our own solar system." They are 2.4 and 2.1 times larger than Earth and orbit TOI 270 every 5.7 and 11.4 days, respectively.
“An interesting aspect of this system is that its planets straddle a well-established gap in known planetary sizes,” said one of the study's co-authors, Fran Pozuelos, in the NASA release. “It is uncommon for planets to have sizes between 1.5 and two times that of Earth for reasons likely related to the way planets form, but this is still a highly controversial topic. TOI 270 is an excellent laboratory for studying the margins of this gap and will help us better understand how planetary systems form and evolve.”
TOI 270 d is attracting interest from Günther’s team, as they believe the equilibrium temperature on the exoplanet is approximately 150 degrees Fahrenheit.
"TOI 270 is perfectly situated in the sky for studying the atmospheres of its outer planets with NASA's future James Webb Space Telescope," the study's co-author Adina Feinstein added in the NASA release. "It will be observable by Webb for over half a year, which could allow for really interesting comparison studies between the atmospheres of TOI 270 c and d."
Günther added that the discovery of TOI-270 will let researchers look at the "'missing link' between rocky Earth-like planets and gas-dominant mini-Neptunes, because here all of these types formed in the same system."
Results of the findings were published in the scientific journal Nature Astronomy.
TESS, which launched in April 2018, replaced the Kepler telescope, which started to malfunction towards the latter part of last year and was eventually retired in October 2018 after discovering more than 2,600 exoplanets, including 18 Earth-sized exoplanets.