NASA's Hubble telescope is employed to gauge the size of the closest Earth-sized planet in transit.

By utilizing NASA's Hubble Space Telescope, scientists have successfully determined the dimensions of the nearest Earth-sized exoplanet that undergoes a transit event across a neighbouring star. This breakthrough enables further exploration into the possible atmospheric composition of this rocky celestial body.

In 2022, NASA's Transiting Exoplanet Survey Satellite (TESS) unveiled the existence of the small-scale celestial body named LTT 1445Ac. However, due to TESS's limited optical resolution, the precise alignment of the planet's orbital plane with respect to its star remained uncertain when observed from Earth. This uncertainty led to the possibility of a grazing transit, where the planet merely brushes against a fraction of the parent star's disk. Consequently, this scenario would yield an imprecise lower boundary for the planet's diameter. Based on Hubble observations, it has been determined that the planet undergoes a complete transit across the star's disk, indicating that its true size is merely 1.07 times that of Earth. Consequently, this planet is classified as a rocky world, similar to Earth, and possesses a comparable surface gravity. However, with a scorching surface temperature of approximately 500 degrees Fahrenheit, it is inhospitable for life as we currently understand it.

Positioned in the constellation Eridanus, the star LTT 1445A is orbited by a planet. This star is part of a triple system consisting of three red dwarf stars, with LTT 1445A being the primary star. Interestingly, LTT 1445A has two other planets that are larger in size compared to LTT 1445Ac. Furthermore, there is a close pair of dwarf stars, LTT 1445B and C, located approximately 3 billion miles away from LTT 1445A. The Hubble telescope has successfully resolved this distant pair of stars. The alignment of these three stars, combined with the edge-on orbit of the LTT 1445B and C pair, suggests that all components within this system lie on the same plane, including the known planets. The value of our measurement lies in its revelation that this planet is likely a nearby terrestrial one. We are eagerly anticipating subsequent observations that will help us gain a better understanding of the diversity of planets present in other star systems.