(55565) 2002 AW197

(55565) 2002 AW₁₉₇ (provisional designation 2002 AW₁₉₇) is a classical, non-resonant trans-Neptunian object from the Kuiper belt in the outermost region of the Solar System, also known as a cubewano. It is the tenth-intrinsically-brightest known trans-Neptunian object,^[23] and with a likely diameter of at least 600 kilometers (400 miles), it is approximately tied with 2002 MS4 and 2013 FY27 (to within measurement uncertainties) as the largest unnamed object in the Solar System. It was discovered at Palomar Observatory in 2002.

(55565) 2002 AW₁₉₇

Hubble Space Telescope image of 2002 AW197 taken in 2006
Discovery[1][2]
Discovered by	Palomar Obs. (team)
Discovery site	Palomar Obs.
Discovery date	10 January 2002
Designations
MPC designation	2002 AW197
Minor planet category	TNO[3] · cubewano[4] p-DP[5] · extended[6] distant[1]
Orbital characteristics[3]
Epoch 31 May 2020 (JD 2459000.5)
Uncertainty parameter 3
Observation arc	21.23 yr (7,756 d)
Earliest precovery date	29 December 1997
Aphelion	53.161 AU
Perihelion	40.922 AU
Semi-major axis	47.042 AU
Eccentricity	0.13009
Orbital period (sidereal)	322.65 yr (117,848 d)
Mean anomaly	294.532°
Mean motion	0° 0m 10.998s / day
Inclination	24.451°
Longitude of ascending node	297.606°
Time of perihelion	≈ 5 May 2078[7] ±4 days
Argument of perihelion	297.494°
Physical characteristics
Mean diameter	768±39 km[8] 734±116 km[9] 700±50 km[10][11] 886 km[12]
Synodic rotation period	8.87±0.01 h[13] 8.78±0.05 h[14] 8.86±0.01 h[15]
Geometric albedo	0.112+0.012 −0.011[8]
Spectral type	IR[16][17] · (moderately red) B–V = 0.920±0.020[18] V–R = 0.560±0.020[18] V–I = 1.170±0.010[17]
Apparent magnitude	20.0 (opposition)[19][20]
Absolute magnitude (H)	3.568±0.046 (V)[21] 3.156±0.059 (R)[22] 3.3 (assumed)[3]

2002 AW₁₉₇ has a rotation period of 8.8 hours and is a moderately red color.^[16] Tancredi notes that photometric observations suggest that it is a spheroid with small albedo spots.^[24] However, its low albedo suggests it does not have the planetary geology expected of a dwarf planet.

Description

2002 AW₁₉₇'s orbit is outside that of Pluto's, with a higher inclination and different orientation

Discovery

2002 AW₁₉₇ was discovered on 10 January 2002, by astronomers at the Palomar Observatory in California.^[1] Astronomers involved in the discovery were Michael Brown, Chad Trujillo, Eleanor Helin, Michael Hicks, Kenneth Lawrence and Steven H. Pravdo.^[2] It is located near the Kuiper cliff.

Orbit and classification

2002 AW₁₉₇ orbits the Sun at a distance of 40.9–53.2 AU once every 322.6 years (over 117,800 days; semi-major axis of 47 AU). Its orbit has an eccentricity of 0.13 and an inclination of 24° with respect to the ecliptic.^[3] The body's observation arc begins with a precovery taken at Haleakala-NEAT/GEODSS (566) in December 1997, more than 4 years prior to its official discovery observation at Palomar.^[1] At 45.4 AU from the Sun,^[19] it continues to slowly approach the Sun until its perihelion passage at 41.1 AU in May 2078.^[7]

Physical characteristics

2002 AW₁₉₇ imaged by Spitzer on 13 April 2004

Combined observations of thermal emissions by the Herschel Space Observatory and Spitzer Space Telescope give a diameter of 768+39
−38 km and a geometric albedo of 0.112+0.012
−0.011.^[8]

Surface

ESO analysis of spectra reveals a strong red slope and no presence of water ice^[25] (in contrast to Quaoar, also red) suggesting organic material (see comparison of colours and typical composition inferred from spectra of the TNOs).

See also

• 174567 Varda – a similar TNO by orbit, size and color
• List of Solar System objects by size