On its mission to discover new planetary worlds, NASA’s Transiting Exoplanet Survey Satellite, or TESS, mission uncovered its smallest exoplanet to date. The planet measures between the sizes of Mars and Earth and orbits a bright, cool star in our solar system’s neighborhood.
This is the tiniest planet discovered by the TESS mission so far. The mission also found that there are two more planets orbiting the same star. However, other than their size, scientists can’t determine much else. They will have to conduct further studies to learn more about the planets, like whether they have atmospheres and which gases could be present in their atmospheres.
“The discovery is a great engineering and scientific accomplishment for TESS,” said Veselin Kostov, an astrophysicist at NASA’s Goddard Space Flight Center and the SETI Institute, in a statement. “For atmospheric studies of small planets, you need short orbits around bright stars, but such planets are difficult to detect. This system has the potential for fascinating future studies.”
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The new findings about the smallest exoplanet to date were published in The Astronomical Journal. The planet is called L 98-59b, and it measures about 80% of Earth’s size and is only 10% smaller than the last record holder discovered by TESS. The star it orbits, L-98-59, is classified as an M dwarf, which is one-third the mass of the sun and located 35 light-years away in the constellation Volans.
While this is the TESS mission’s smallest exoplanet to date, the Kepler space telescope uncovered a planet that is only 20% larger than the moon. Thus, the TESS mission has a ways to go before it will beat that record. The two other planets, L 98-59c and L 98-59d, are about 1.4 and 1.6 times bigger than Earth, respectively, and they were discovered using the transit method, or gaps of darkness in the host star caused by planets passing in front of them.
“If you have more than one planet orbiting in a system, they can gravitationally interact with each other,” said study co-author Jonathan Brande, an astrophysicist at Goddard and the University of Maryland, College Park. “TESS will observe L 98-59 in enough sectors that it may be able to detect planets with orbits around 100 days. But if we get really lucky, we might see the gravitational effects of undiscovered planets on the ones we currently know.”
Scientists have big plans for the TESS mission, the successor of the Kepler space telescope, which shut down in October. Scientists plan to build a database of small, rocky planets with short orbits around brighter stars which are scheduled for study via the upcoming James Webb Space Telescope.
“If we viewed the Sun from L 98-59, transits by Earth and Venus would lead us to think the planets are almost identical, but we know they’re not,” co-author and Goddard astrophysicist Joshua Schlieder said. “We still have many questions about why Earth became habitable and Venus did not. If we can find and study similar examples around other stars, like L 98-59, we can potentially unlock some of those secrets.”
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