NASA's TESS Observes Interstellar Comet 3I/ATLAS to Study Rotation

NASA's Transiting Exoplanet Survey Satellite (TESS), primarily designed to detect exoplanets, has recently observed interstellar comet 3I/ATLAS during its journey out of the solar system. Between January 15 and January 22, TESS captured images of the comet, appearing as a bright, fast-moving dot with a faint tail against a backdrop of stars.

Daniel Muthukrishna of the Massachusetts Institute of Technology compiled these images into a 28-hour video, illustrating the comet's trajectory. The observations were briefly interrupted when TESS entered 'safe mode' due to a solar panel issue, resulting in a time gap from January 15 to January 18.

Scientists aim to use this dataset to study the comet's activity and rotation, providing insights into its dust and gas emissions and the spin rate of its nucleus. TESS's measurements indicate that comet 3I/ATLAS has an apparent magnitude of about 11.5, making it approximately 100 times fainter than the naked eye can perceive but observable with telescopes.

Although TESS is primarily tasked with finding exoplanets through the transit method, its wide field of view and continuous monitoring capabilities also make it valuable for detecting and tracking nearby objects like comets and asteroids over extended periods. Notably, TESS observed comet 3I/ATLAS in May 2025, two months before its official discovery, allowing astronomers to retrospectively analyze its movements and gather additional data.