C/1999 S4 (LINEAR)

For other comets of the same name, see List of comets discovered by the LINEAR project.

C/1999 S4 (LINEAR) was a hyperbolic comet discovered by the Lincoln Near-Earth Asteroid Research survey on 27 September 1999.^[1]

C/1999 S4 (LINEAR)

Hubble image of C/1999 S4 disintegrating on 5 August 2000
Discovery[1]
Discovered by	LINEAR (704)
Discovery site	Socorro, New Mexico
Discovery date	27 September 1999
Designations
Alternative designations	CJ99S040[1]
Orbital characteristics[2][3]
Epoch	13 February 2000 (JD 2451587.5)
Observation arc	300 days
Number of observations	1,230
Aphelion	~1400 AU
Perihelion	0.765 AU
Semi-major axis	~700 AU
Eccentricity	1.00010
Orbital period	~18,700 years
Inclination	149.38°
Longitude of ascending node	83.181°
Argument of periapsis	151.05°
Last perihelion	26 July 2000
Earth MOID	0.174 AU
Jupiter MOID	0.802 AU
Physical characteristics[4][5]
Dimensions	0.9 km (0.56 mi)
Comet total magnitude (M1)	9.6
Apparent magnitude	6.6–6.8 (2000 apparition)

Physical properties

Its nucleus was estimated to be about 0.9 km in diameter.^[4] Before the comet broke up, the (dust and water) nucleus erosion rate was about 1 cm per day.^[4] The comet brightened near 5 July 2000, and underwent a minor fragmentation event.^[6] The comet brightened again around 20 July 2000, and then disintegrated.^[7] The published optical and most radio data support that the main nuclear decay started 23 July 2000.^[4] The dust cloud expanded at about 20 m/s (66 ft/s) while the fragments expanded at around 7 m/s (23 ft/s).^[4] Other comets are known to have disappeared, but Comet LINEAR is the first one to have been caught in the act.^[8]

Orbit

The orbit of a long-period comet is properly obtained when the osculating orbit is computed at an epoch after leaving the planetary region and is calculated with respect to the center of mass of the Solar System. Using JPL Horizons, the barycentric orbital elements for epoch 2010-Jan-01 generate a semi-major axis of 700 AU, an aphelion distance of 1400 AU, and a period of approximately 18,700 years.^[2]

The comet made its closest approach to the Earth on 22 July 2000, at a distance of 0.372 AU (55.7 million km).^[3] It came to perihelion on 26 July 2000, at a distance of 0.765 AU (114.4 million km) from the Sun.^[3]