C/1999 T1 (McNaught–Hartley)

For other comets discovered by Robert H. McNaught, see Comet McNaught (disambiguation).

C/1999 T1 (McNaught–Hartley) is a near-parabolic long-period comet, discovered by Robert H. McNaught and Malcolm Hartley at the Siding Spring Observatory in 1999.^[4]

C/1999 T1 (McNaught-Hartley)

Discovery[1]
Discovered by	Robert H. McNaught Malcolm Hartley
Discovery site	Siding Spring Observatory
Discovery date	7 October 1999
Designations
Alternative designations	Comet McNaught-Hartley
Orbital characteristics[2][3]
Epoch	2 December 2000 (JD 2451880.5)
Observation arc	787 days (2.15 years)
Number of observations	661
Aphelion	16,247 AU
Perihelion	1.172 AU
Semi-major axis	8,124 AU
Eccentricity	0.99985
Orbital period	732,246 years
Inclination	79.975°
Longitude of ascending node	182.483°
Argument of periapsis	344.758°
Last perihelion	13 December 2000
TJupiter	0.234
Earth MOID	0.19397 AU
Jupiter MOID	3.41621 AU
Physical characteristics
Synodic rotation period	1–10 days
Comet total magnitude (M1)	8.3

Observations

Comet McNaught–Hartley was a magnitude 15 object upon discovery on October 7, 1999.^[4] Gas emissions were measured in x-ray light by the Chandra observatory (alongside C/1999 S4 (LINEAR)) between 8–14 January 2001.^[5][6] Observations of its coma between January 26 and February 5, 2001 show that the nucleus has a rotation period between 1 and 10 days.^[7]

Exploration

Main article: Ulysses (spacecraft) § Comet C/1999 T1 (McNaught–Hartley)

Research published in 2004 found that the Ulysses spacecraft had likely detected ions from the comet tail of C/1999 T1. This was the spacecraft's second encounter with a comet tail, after Comet Hyakutake in 1996.^[8][9]

See also

• Comet McNaught