| Discovery[1][2] | |
|---|---|
| Discovered by | Hannes Gröller |
| Discovery site | Kitt Peak, Arizona (Bok Telescope) |
| Discovery date | 20 February 2025 |
| Orbital characteristics[3] | |
| Epoch | 24 June 2024 (JD 2460485.5) |
| Observation arc | 6.90 years (2,522 days) |
| Earliestprecovery date | 6 June 2018 |
| Number of observations | 66 |
| Perihelion | 14.123 AU |
| Eccentricity | 1.00302 |
| Orbital period | ~6 million years (inbound) |
| Inclination | 84.491° |
| 312.89° | |
| Argument of periapsis | 185.85° |
| Mean anomaly | –0.004° |
| Next perihelion | 18 May 2028 |
| EarthMOID | 13.143 AU |
| JupiterMOID | 8.826 AU |
| Physical characteristics[4] | |
Mean radius | ≥ 0.4 km (0.25 mi) |
| Comet total magnitude (M1) | 6.6 |
Comet Gröller, also known asC/2025 D1 (Gröller), is a very distantnon-periodic comet discovered by Hannes Gröller of theCatalina Sky Survey on 20 February 2025. It is the comet with the most distant perihelion ever known,[5] which will approach the Sun no closer than 14.12 AU (2.112 billion km) by May 2028,[3] surpassing the record previously held byC/2003 A2 (Gleason) by 2.7 AU.[5][6]
It was Hannes Gröller's fourth comet discovery since 2019.[a]
The comet was discovered by Hannes Gröller using the 2.25 m (7.4 ft)Bok Telescope of theKitt Peak Observatory in Arizona.[2] Images obtained through stacking of 30-second exposures show a magnitude 20.6 object with a condensedcoma measuring 3 arcseconds across.[1][7] Amateur astronomer Sam Deen found severalprecovery observations of C/2025 D1 from 2018, when the comet was more than 21 AU (3.1 billion km) from the Sun (beyond the orbit ofUranus).[5] This makes C/2025 D1 one of the few known "ultradistant comets" that have been observed beyond 20 AU (3.0 billion km) from the Sun.[5] The ultradistant comets, which include the giantOort cloud cometC/2014 UN271 (Bernardinelli–Bernstein), are believed to containsupervolatile compounds such ascarbon monoxide andcarbon dioxide, which are known to easily vaporize at low temperatures far from the Sun.[5]
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 60 AU (9.0 billion km).[4] It will reach its next perihelion on 18 May 2028,[3] and is expected to be ejected from the Solar System on its outbound flight.[4]
Other ultradistant comets:
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