C/2025 D1 (Gröller)

Comet Gröller, also known as C/2025 D1, is a very distant hyperbolic 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,^[3] which will approach the Sun no closer than 14.12 AU (2.112 billion km) by May 2028,^[2] surpassing the record previously held by C/2003 A2 (Gleason) by 2.7 AU.^[3][4]

C/2025 D1 (Gröller)

Discovery[1]
Discovered by	Hannes Gröller
Discovery site	Kitt Peak, Arizona (Bok Telescope)
Discovery date	20 February 2025
Orbital characteristics[2]
Epoch	27 December 2023 (JD 2460305.5)
Observation arc	6.73 years (2,457 days)
Earliest precovery date	6 June 2018
Number of observations	41
Perihelion	14.123 AU
Eccentricity	1.00282
Inclination	84.507°
Longitude of ascending node	312.88°
Argument of periapsis	185.84°
Mean anomaly	–0.004°
Next perihelion	18 May 2028
Earth MOID	13.142 AU
Jupiter MOID	8.825 AU
Comet total magnitude (M1)	6.5

Observational history

The comet was discovered by Hannes Gröller using the 2.25 m (7.4 ft) Bok Telescope of the Kitt Peak Observatory in Arizona.^[1] Images obtained through stacking of 30-second exposures show a magnitude 20.6 object with a condensed coma measuring 3 arcseconds across.^[5][6]