145452 Ritona

145452 Ritona
	Ritona imaged by the Hubble Space Telescope on 25 April 2010
Discovery
Discovered by	Andrew C. Becker; Andrew W. Puckett; Jeremy M. Kubica;
Discovery site	Apache Point Obs.
Discovery date	10 September 2005
Designations
MPC designation	(145452) Ritona
Pronunciation	/ˈrɪtənə/
Named after	Ritona
Alternative designations	2005 RN43
Minor planet category	TNO; classical (hot); distant; Scat-Ext;
Orbital characteristics (barycentric)
	Epoch 5 May 2025 (JD 2460800.5)
	Uncertainty parameter 0
Observation arc	70.99 yr (25930 days)
Earliest precovery date	2 June 1954
Aphelion	42.450 AU
Perihelion	40.575 AU
Semi-major axis	41.512 AU
Eccentricity	0.0226
Orbital period (sidereal)	267.29 yr (97,627 d)
Mean anomaly	352.812°
Mean motion	0° 0m 13.275s / day
Inclination	19.274°
Longitude of ascending node	186.989°
Time of perihelion	≈ 15 June 2029
Argument of perihelion	172.899°
Known satellites	0
Physical characteristics
Mean diameter	679+55; −73 km
Sidereal rotation period	6.946±0.05 h (single-peaked); or 13.892±0.05 h (double-peaked);
Geometric albedo	0.107+0.029; −0.018
Temperature	43.2 K (perihelion)
Spectral type	CO; 2-type ("double-dip"); IR–RR (red); B–V = 0.95±0.02; V–R = 0.59±0.01; V–I = 1.08±0.02;
Apparent magnitude	≈ 20 (average)
Absolute magnitude (H)	3.882±0.036 (2016); 3.89±0.05 (2012); 3.69 (JPL);

145452 Ritona (provisional designation 2005 RN₄₃) is a large trans-Neptunian object orbiting the Sun in the Kuiper belt. It was discovered on 10 September 2005 by astronomers Andrew Becker, Andrew Puckett and Jeremy Kubica at Apache Point Observatory in Sunspot, New Mexico. Ritona has a measured diameter of 679+55
−73 km, which is large enough that some astronomers consider it a possible dwarf planet.

Ritona has a dark and reddish surface made of water ice, carbon dioxide ice, carbon monoxide ice, and various organic compounds (tholins). Observations by the James Webb Space Telescope have shown that carbon dioxide ice is more abundant than water ice in Ritona's surface, which suggests that there is a thin layer of carbon dioxide ice covering Ritona's surface. Ritona is not known to have any natural satellites or moons, which means there is currently no way to measure its mass and density.