LTT 1445Ac, a terrestrial planet in the triple star system LTT 1445, is only 1.07 times the size of Earth, according to a paper to be published in the Astronomical Journal.
LTT 1445 is a hierarchical trio of M dwarfs located 22.5 light-years away in the constellation of Eridanus.
Also known as TIC 98796344, TOI 455, L 730-18 or BD-17 588, the system consists of the brighter star LTT 1445A and the fainter visual binary LTT 1445BC.
LTT 1445A hosts at least three exoplanets: LTT 1445Ab, LTT 1445Ac and LTT 1445Ad.
“Photometry from NASA’s Transiting Exoplanet Survey Satellite (TESS) revealed two small transiting planets in the LTT 1445 system: planet b and planet c,” said Dr. Emily Pass from the Harvard & Smithsonian’s Center for Astrophysics and her colleagues.
“High-precision radial velocity follow-up of LTT 1445A from the ESPRESSO spectrograph on ESO’s Very Large Telescope also yielded an additional candidate planet d, which is likely non-transiting.”
“LTT 1445A is the nearest M dwarf with a known transiting planet,” they added.
“Planets b and c therefore offer some of the most favorable conditions to characterize the atmospheres of terrestrial exoplanets.”
Previous studies of LTT 1445Ac concluded that the light curve from TESS was consistent with both grazing and non-grazing geometries.
As a result, the radius and hence density of the planet remained unknown.
“There was a chance that this system has an unlucky geometry and if that’s the case, we wouldn’t measure the right size,” Dr. Pass said.
“But with the capabilities of the NASA/ESA Hubble Space Telescope we nailed its diameter.”
In their research, the astronomers observed the LTT 1445 system for six spacecraft orbits of Hubble, including one partial transit of LTT 1445Ac.
The observations show that the planet makes a normal transit fully across the star’s disk, yielding a true size of only 1.07 times Earth’s diameter.
This means the planet is a rocky world, like…
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