WASHINGTON, January 21, 2026, 12:34 EST
NASA has retasked its Transiting Exoplanet Survey Satellite (TESS) to run a special observation of interstellar comet 3I/ATLAS, temporarily interrupting its Sector 99 schedule, the agency said. The Jan. 15–22 pointing will deliver continuous photometry — precise brightness measurements — and NASA said the data will be calibrated and publicly archived with no proprietary period.
The move reflects a short window. NASA says 3I/ATLAS is only the third known interstellar object — after 1I/’Oumuamua (2017) and 2I/Borisov (2019) — and its hyperbolic track means it will not stay bound to the sun. It poses no danger to Earth and should remain observable with a small telescope into spring, NASA says.
Fresh measurements from NASA’s SPHEREx observatory suggest the comet has become far more active since its late-October perihelion, when it passed closest to the sun. A team analysing SPHEREx data said carbon monoxide and water-vapor emissions were about 20 times stronger in December than in August, a sign that a wider mix of ices is sublimating — turning straight into gas. They also reported new signatures from cyanide and organic gases that were not seen before perihelion.
Carey Lisse of the Johns Hopkins University Applied Physics Laboratory and colleagues wrote that SPHEREx re-observed 3I/ATLAS in mid-December, “finding a much more active object compared to the August 2025 SPHEREx pre-perihelion observations”. The group said the data show a coma — the gas-and-dust cloud around the nucleus — with emissions from cyanide (CN), water, carbon dioxide and carbon monoxide, along with organics. Sci.News: Breaking Science News
SPHEREx, short for Spectro-Photometer for the History of the Universe, Epoch of Reionization and Ices Explorer, measures light in dozens of infrared colors to help identify gases and dust, NASA said. The mission tracked 3I/ATLAS for about a week in August, laying down a pre-perihelion baseline that other observatories, including Hubble and Webb, have been building on.
But the December SPHEREx results are still being refined. In their preprint, the authors said “No obvious jet or anti-solar tail structures were found” during the Dec. 8–15 run, and they flagged the work as preliminary ahead of a fuller analysis expected before another SPHEREx pass in April 2026. arXiv
NASA has been pulling images and spectra from spacecraft spread across the solar system — including three missions at Mars — to follow 3I/ATLAS as it heads outbound, the agency said. The agency expects to keep watching as the comet moves toward the orbit of Jupiter in spring 2026.
3I/ATLAS was first spotted by a NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope in Rio Hurtado, Chile and reported to the Minor Planet Center on July 1, 2025, Reuters reported. University of Hawaii astronomer Larry Denneau, a co-principal investigator for ATLAS, said then “there are many efforts underway to observe this object with larger telescopes to determine composition”. Reuters
