Comet Gröller, also known as C/2025 D1 (Gröller), is a very distant non-periodic comet discovered by Hannes Gröller of the Catalina Sky Survey on 20 February 2025. It is the comet with the most distant perihelion ever known, which will approach the Sun no closer than by May 2028, surpassing the record previously held by C/2003 A2 (Gleason) by 2.7 AU.
It was Hannes Gröller's fourth comet discovery since 2019.
Observational history The comet was discovered by Hannes Gröller using the Bok Telescope of the Kitt Peak Observatory in Arizona. Images obtained through stacking of 30-second exposures show a magnitude 20.6 object with a condensed coma measuring 3 arcseconds across. Amateur astronomer Sam Deen found several precovery observations of C/2025 D1 from 2018, when the comet was more than from the Sun (beyond the orbit of Uranus). This makes C/2025 D1 one of the few known "ultradistant comets" that have been observed beyond from the Sun. The ultradistant comets, which include the giant Oort cloud comet (Bernardinelli–Bernstein), are believed to contain supervolatile compounds such as carbon monoxide and carbon dioxide, which are known to easily vaporize at low temperatures far from the Sun.
Orbit Astrometric measurements and orbital calculations reveal that C/2025 D1 is a dynamically new comet from the Oort cloud, with its previous perihelion distance approximately 6 million years ago were estimated to be greater than or equal to . It will reach its next perihelion on 18 May 2028, and is expected to be ejected from the Solar System on its outbound flight.
See also Other ultradistant comets: Comet Hale–Bopp C/2010 U3 (Boattini) C/2017 K2 (PanSTARRS) (Bernardinelli–Bernstein) C/2019 E3 (ATLAS)
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References
External links
at the Minor Planet Center database