(79983) 1999 DF9

(79983) 1999 DF₉ (provisional designation 1999 DF₉) is a trans-Neptunian object of the Kuiper belt, classified as a non-resonant cubewano, that measures approximately 270 kilometers in diameter.

(79983) 1999 DF₉

Discovery[1]
Discovered by	J. X. Luu C. Trujillo D. C. Jewitt
Discovery site	Kitt Peak National Obs.
Discovery date	20 February 1999
Designations
MPC designation	(79983) 1999 DF9
Alternative designations	1999 DF9
Minor planet category	TNO[1] · cubewano[2][3]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 2
Observation arc	17.06 yr (6,231 days)
Aphelion	53.567 AU
Perihelion	39.830 AU
Semi-major axis	46.698 AU
Eccentricity	0.1471
Orbital period (sidereal)	319.12 yr (116,560 days)
Mean anomaly	19.489°
Mean motion	0° 0m 11.16s / day
Inclination	9.8105°
Longitude of ascending node	334.84°
Argument of perihelion	178.63°
Physical characteristics
Dimensions	265 km (calculated)[4] 306 km[3]
Synodic rotation period	6.65 h[5]
Geometric albedo	0.10 (assumed)[4]
Spectral type	B–V = 0.920±0.060[6] V–R = 0.710±0.050[6] V–I = 1.360±0.060[6]
Absolute magnitude (H)	5.797±0.110 (R)[7] · 6.0[1][4]

Discovery

It was discovered on 20 February 1999, by American and British astronomers Jane Luu, Chad Trujillo and David C. Jewitt at the U.S. Kitt Peak National Observatory in Arizona.^[8] As no precoveries were taken, the minor planet's observation arc begins with its discovery observation in 1999.^[8]

Classification and orbit

The minor planet is a classical Kuiper belt object or "cubewano", which are not in an orbital resonance with Neptune and do not cross the giant planet's orbit. It orbits the Sun at a distance of 39.8–53.6 AU once every 319 years and 1 month (116,560 days). Its orbit has an eccentricity of 0.15 and an inclination of 10° with respect to the ecliptic.^[1] This makes it a relatively eccentric body for a classical Kuiper belt object, which typically have low-eccentricities of 0.10 or less.

Physical characteristics

In February 2001, a rotational lightcurve was published for this minor planet from photometric observations by Portuguese astronomer Pedro Lacerda and the discovering astronomer Jane Luu. Lightcurve analysis gave a relatively short rotation period of 6.65 hours with a brightness variation of 0.40 magnitude (U=2).^[5]

The Collaborative Asteroid Lightcurve Link assumes a low albedo of 0.10 and calculates a mean-diameter of 265 kilometers, based on an absolute magnitude of 6.0,^[4] while Johnston's Archive give a diameter of 306 kilometers for an albedo of 0.09.^[3]

Numbering and naming

This minor planet was numbered by the Minor Planet Center on 4 May 2004.^[9] As of 2025, it has not been named.^[8]