In 2023, astronomers discovered a new exoplanet named Gaia23bra b, which is located nearly 40,000 light-years from Earth. This significant finding was made possible by NASA's Transiting Exoplanet Survey Satellite (TESS), which identified the planet despite it being 150 light-years outside its typical search radius. Gaia23bra b is 1.6 times the size of Jupiter and orbits an orange dwarf star that has about 80% of the Sun's mass. The discovery was initially noted by the European Space Agency's Gaia Telescope, which had limited observations of the planet.
The TESS spacecraft's ability to monitor the same area of the sky with denser time coverage allowed researchers to detect additional features in the light curve caused by the planet. Mallory Harris, a Ph.D. candidate at the University of New Mexico, led a study that highlighted the importance of TESS in identifying such distant planets. The findings were published on July 1 in The Astrophysical Journal Letters, showcasing the potential for TESS to uncover more microlensing planets that were previously overlooked.
Typically, TESS focuses on finding star-hugging transitioning planets, making the discovery of Gaia23bra b particularly rare. Diana Dragomir, a professor at the University of New Mexico and co-author of the study, noted that when TESS launched, no one anticipated it would be capable of finding such large planets at significant distances from their host stars. This discovery suggests that there may be many more microlensing planets hidden within TESS's data.
Microlensing is a phenomenon that occurs when two stars align closely from our perspective, causing light from a more distant star to bend due to the warped space-time created by the nearer star's mass. Although microlensing has revealed less than 5% of known exoplanets, the discovery of Gaia23bra b indicates that TESS may be able to identify more planets through this method. NASA's upcoming Nancy Grace Roman Space Telescope is expected to further explore this area, aiming to reveal an estimated 1,000 microlensing planets and around 100,000 transiting planets when it launches later this year.
