Hubble Space Telescope Determines the Size of the Closest Earth-sized Transiting Planet

The NASA/ESA Hubble Space Telescope has made an exciting discovery, measuring the size of the nearest Earth-sized exoplanet that passes in front of its neighboring star. This opens up the opportunity for further studies to explore the atmosphere of this rocky world.

The exoplanet, named LTT 1445Ac, was initially discovered by NASA’s Transiting Exoplanet Survey Satellite in 2022. However, the exact geometry of the planet’s orbit in relation to its star was uncertain due to the limitations of TESS’s optical resolution. This uncertainty meant that the previously measured size could have been inaccurate.

Fortunately, the Hubble Space Telescope’s capabilities allowed scientists to accurately measure the diameter of LTT 1445Ac. Through observations, it was determined that the planet fully transits across the star’s disk, resulting in a true size of only 1.07 times the diameter of Earth. This means that LTT 1445Ac is a rocky world with similar surface gravity to our own planet. However, with a surface temperature of approximately 260 degrees Celsius, it is far too hot to sustain life as we know it.

LTT 1445Ac orbits a star called LTT 1445A, which is part of a triple system consisting of three red dwarf stars located 22 light-years away in the constellation Eridanus. The star has two other reported planets that are larger than LTT 1445Ac. Additionally, Hubble observations have also resolved a tight pair of dwarf stars, LTT 1445B and C, which are about 4.8 billion kilometers away from LTT 1445A. The alignment of these stars and the edge-on orbit of the BC pair suggest that everything in the system, including the known planets, is coplanar.

The discovery of LTT 1445Ac as an Earth-sized exoplanet that can be studied in detail is significant. Transiting planets like this one provide an opportunity to analyze their atmospheres using spectroscopy. The Hubble Space Telescope, along with the upcoming James Webb Space Telescope, will play an important role in characterizing the atmospheres of these exoplanets. Scientists are excited about the potential to better understand the diversity of planets around other stars through follow-up observations.

Emily Pass of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, USA, expressed enthusiasm about the measurement, stating that it confirms LTT 1445Ac as a nearby terrestrial planet. This proximity allows for detailed studies of its atmospheric properties. Professor Laura Kreidberg of the Max Planck Institute for Astronomy in Heidelberg, Germany, who was not involved in this study, emphasized the importance of Hubble’s role in characterizing exoplanets. She highlighted the rarity of terrestrial planets that are close enough for atmospheric analysis and described LTT 1445Ac as one of the best planets to study in the sky.

The Hubble Space Telescope is a collaborative project between ESA and NASA, and its contribution to the field of exoplanet research continues to be invaluable. This latest discovery of an Earth-sized exoplanet paves the way for future investigations into the atmospheres of planets beyond our solar system. The scientific community eagerly awaits further insights into the diversity and conditions of planets around other stars.