Free Astronomy Magazine January-February 2024

36 JANUARY-FEBRUARY 2024 ASTRO PUBLISHING was first discovered by NASA’s Tran- siting Exoplanet Survey Satellite in 2022. But the geometry of the planet’s orbital plane relative to its star as seen from Earth was uncer- tain because TESS does not have the required optical resolution. This means the detection could have been a so-called grazing transit, where a planet only skims across a by NASA/ESA Bethany Downer T he NASA/ESA Hubble Space Telescope has measured the size of the nearest Earth-sized exoplanet that passes across the face of a neighbouring star. This align- ment, called a transit, opens the door to follow-on studies to see what kind of atmosphere, if any, the rocky world might have. The diminutive planet, LTT 1445Ac, Hubble measures the size of the nearest transiting Earth-sized planet T his is an artist’s concept of the nearby exoplanet, LTT 1445Ac, which is the size of Earth. The planet orbits a red dwarf star. The star is in a triple system, with two closely or- biting red dwarfs seen at upper right. The black dot in front of the foreground star is planet LTT 1445Ab, transiting the face of the star. [NASA, ESA, L. Hustak (STScI)]