In a significant breakthrough, NASA’s Hubble Space Telescope has accurately measured the size of the nearest Earth-sized exoplanet, LTT 1445Ac, providing essential information for follow-on studies to explore its potential atmosphere. The transit of this rocky world across its neighboring star’s face, known as a transit, was observed, allowing astronomers to determine its diameter with unprecedented precision.
Discovery and Uncertainties
Discovered by NASA’s Transiting Exoplanet Survey Satellite (TESS) in 2022, LTT 1445Ac posed uncertainties due to the limited optical resolution of TESS. The geometry of the planet’s orbital plane relative to its star was unclear, raising the possibility of an inaccurate measurement of its diameter, especially if it had a grazing transit.
Hubble’s Precision Measurements
Hubble’s observational capabilities played a crucial role in resolving these uncertainties. The telescope observed that LTT 1445Ac makes a normal transit fully across the star’s disk, providing a precise size measurement equivalent to only 1.07 times Earth’s diameter. This revelation confirms that the planet is a rocky world with a surface gravity similar to Earth. However, its surface temperature of approximately 500 degrees Fahrenheit makes it inhospitable for life as we know it.
Characteristics of LTT 1445Ac
The exoplanet orbits the star LTT 1445A, part of a triple system with three red dwarf stars located 22 light-years away in the constellation Eridanus. LTT 1445A has two other reported planets, larger than LTT 1445Ac. The Hubble observations also resolved a tight pair of dwarf stars, LTT 1445B and C, situated about 3 billion miles away from LTT 1445A. The alignment of the three stars and the edge-on orbit of the BC pair suggest a co-planar system, including the known planets.
Future Atmospheric Studies
The confirmation of LTT 1445Ac as a nearby terrestrial planet opens the door for atmospheric studies using spectroscopy. The James Webb Space Telescope, alongside Hubble, will contribute to advancing our understanding of the diversity of planets around other stars. Researchers eagerly anticipate follow-on observations to delve deeper into the characteristics of this intriguing exoplanet.
This groundbreaking research has been accepted for publication in The Astronomical Journal. The Hubble Space Telescope is a project of international cooperation between NASA and ESA. NASA’s Goddard Space Flight Center manages the telescope, while the Space Telescope Science Institute conducts Hubble science operations.
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