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The discovery and confirmation of TOI-4465 b, a giant planet about 1.25 times the size of Jupiter and nearly six times its mass, is reported. This planet orbits a Sun-like star approximately 122 parsecs (about 398 light-years) away. It was initially detected as a single transit event—when a planet passes in front of its star—in data from Sector 40 of NASA’s Transiting Exoplanet Survey Satellite (TESS). Radial velocity measurements, which track a star’s motion caused by an orbiting planet, revealed that TOI-4465 b completes an orbit roughly every 102 days and follows a somewhat elliptical path (eccentricity = 0.24 ± 0.01).
TESS later observed the star during Sectors 53 and 80, but no additional transits were detected, as the planet was not expected to pass in front of the star during those times based on its orbital period. A coordinated global effort was launched to observe the next predicted transit, resulting in successful observations of the approximately 12-hour-long event from multiple locations worldwide. These included contributions from 24 citizen scientists, confirming the planet’s orbital period of about 102 days.
TOI-4465 b is relatively dense (about 3.73 grams per cubic centimeter) and has a moderate temperature, estimated between 375 and 478 Kelvin (roughly 212°F to 404°F). According to models of giant planet structure, it likely contains a high amount of heavy elements, consistent with having accumulated icy material during the later stages of its formation. The planet is also considered a promising target for future studies of its atmosphere and orbital tilt (obliquity). Confirming long-period planets like TOI-4465 b—especially those initially seen in only one transit—is essential for improving understanding of how planets form and how common they are in the outer regions of planetary systems.
Figure 1. SED of TOI-4465. Red symbols represent the observed photometric measurements, where the horizontal bars represent the effective width of the passband. Blue symbols are the model fluxes from the best-fit PHOENIX atmosphere model (black). The inset shows the absolute flux-calibrated Gaia spectrophotometry as a gray swathe overlaid on the model (black).
