C/2009 F6 (Yi–SWAN)

For other comets discovered by the SWAN instrument, see Comet SWAN.

C/2009 F6 (Yi–SWAN) is a non-periodic comet which first appeared in March 2009.

C/2009 F6 (Yi–SWAN)

Discovery
Discovered by	Dae-am Yi Robert D. Matson (SWAN)
Discovery site	SOHO
Discovery date	26 March 2009
Orbital characteristics[1][2]
Epoch	22 May 2009 (JD 2454973.5)
Observation arc	330 days
Earliest precovery date	25 March 2009
Number of observations	487
Aphelion	904 AU
Perihelion	1.274 AU
Semi-major axis	453 AU
Eccentricity	0.99751
Orbital period	~9,600 years
Inclination	85.764°
Longitude of ascending node	278.68°
Argument of periapsis	129.77°
Mean anomaly	0.0012°
Last perihelion	8 May 2009
TJupiter	0.113
Earth MOID	0.505 AU
Jupiter MOID	0.724 AU
Physical characteristics[3][4]
Mean radius	2.54 km (1.58 mi)
Comet total magnitude (M1)	9.7
Comet nuclear magnitude (M2)	13.2
Apparent magnitude	8.3 (2009 apparition)

Discovery and observations

On 4 April 2009, Robert D. Matson reported the discovery of a comet spotted from images taken by the SWAN instrument of the SOHO spacecraft.^[5] Around the same time, Hereupon H. Yamaoka of the University of Tokyo received an email from South Korean astronomer, Dae-am Yi, where he reported that he had discovered the comet nine days earlier on 26 March, at the time a 12th-magnitude object within the constellation Lacerta.^[4]

The comet was too dim to be seen by the naked eye, though it was observed through small telescopes. It is hard to watch because it is small with a tiny tail in the visible-light spectrum. The comet reached a peak magnitude of 8.3 on 6 April,^[5] and passed 1.5 degrees south of the Double cluster in Perseus on 23 April.^[6] Preliminary calculations of its orbit by Brian G. Marsden indicate the comet is traveling in a highly inclined parabolic orbit, tipped 85.7° to the plane of the ecliptic. It reached perihelion on 8 May, where it came as close as 1.27 AU (190 million km) from the Sun.^[6]