167P/CINEOS

167P/CINEOS
Discovery
Discovered by	CINEOS
Discovery date	August 10, 2004
Designations
Alternative designations	P/2004 PY42
Orbital characteristics
Epoch	2066-03-11
Observation arc	9.35 years
Aphelion	20.8 AU
Perihelion	11.77 AU; (outside Saturn's orbit)
Semi-major axis	16.28 AU
Eccentricity	0.27705
Orbital period	65.67 yr
Max. orbital speed	9.8 km/s
Min. orbital speed	5.6 km/s (2033-Nov-30)
Inclination	19.0529°
Last perihelion	April 24, 2001
Next perihelion	March 18, 2066; March 22, 2066; March 23, 2066;
TJupiter	3.52
Physical characteristics
Dimensions	66.17±22.9 km
Geometric albedo	0.053±0.019
Spectral type	sdfg

167P/CINEOS (P/2004 PY₄₂) is a large periodic comet and active, grey centaur, approximately 66 kilometers (41 miles) in diameter, orbiting the Sun outside the orbit of Saturn. It was discovered on August 10, 2004, by astronomers with the CINEOS survey at Gran Sasso in Italy. It is one of only a handful known Chiron-type comets.

The comet nucleus (~66 km) is roughly half the size of C/2014 UN271 (Bernardinelli–Bernstein) and it has a similar perihelion point just outside the orbit of Saturn.

Large comets with perihelion near Saturn's orbit at 10 AU
Comet	Nucleus diameter	Perihelion (Sun approach)	Perihelion velocity
95P/Chiron	215 km	8.5 AU	12.0 km/s
C/2014 UN271 (Bernardinelli–Bernstein)	120 km	10.95 AU	12.7 km/s
167P/CINEOS	66 km	11.77 AU	9.8 km/s^[1]

Description

Due to its high Jupiter tisserand of 3.5, and a semi-major axis larger than that of Jupiter, 167P/CINEOS is classified as a Chiron-type comet, named after the groups namesake, 2060 Chiron or 95P/Chiron, designated as both minor planet and comet.^[4]

167P/CINEOS was first reported as a minor planet, designated 2004 PY₄₂, but was found to have a very faint asymmetric cometary coma.^[5] Contrary to Chiron, which is the prototype object for the dynamical group of centaurs, 167P/CINEOS has no "dual status" as comet and minor planet, and demonstrates the inconsistencies in applying the current rules for designating small Solar System bodies.^[6] 167P/CINEOS not only has orbital parameters similar to those of Chiron, but also a low B–R magnitude of 1.29±0.03, which places it into the group grey centaurs.^[7]