(307261) 2002 MS4
(307261) 2002 MS4 (provisional designation 2002 MS4) is a large trans-Neptunian object in the Kuiper belt, which is a region of icy planetesimals beyond Neptune. It was discovered on 18 June 2002 by Chad Trujillo and Michael Brown during their search for bright, Pluto-sized Kuiper belt objects at Palomar Observatory. To within measurement uncertainties, 2002 MS4, 2002 AW197, and 2013 FY27 have a diameter close to 800 km (500 mi), which makes them the largest unnamed objects in the Solar System. 2002 MS4 is large enough that astronomers consider it a possible dwarf planet.
2002 MS4 imaged by the Hubble Space Telescope on 9 April 2006 | |
| Discovery | |
|---|---|
| Discovered by | Chadwick A. Trujillo Michael E. Brown |
| Discovery site | Palomar Obs. |
| Discovery date | 18 June 2002 |
| Designations | |
| 2002 MS4 | |
| TNO · cubewano (hot): 56 distant · Scat-Ext | |
| Orbital characteristics (barycentric) | |
| Epoch 25 February 2023 (JD 2460000.5) | |
| Uncertainty parameter 2 | |
| Observation arc | 66.22 yr (24,188 d) |
| Earliest precovery date | 8 April 1954 |
| Aphelion | 47.801 AU |
| Perihelion | 35.677 AU |
| 41.739 AU | |
| Eccentricity | 0.14524 |
| 269.48 yr (98,429 d) | |
| 226.844° | |
| 0° 0m 13.167s / day | |
| Inclination | 17.693° |
| 216.075° | |
| ≈ 10 June 2123 ±0.6 days | |
| 214.575° | |
| Physical characteristics | |
| Dimensions | (823±20) × (770±34) km (projected) |
Mean diameter | 796±24 km |
| Flattening | ≥0.066±0.034: 5 |
| 14.251 h: 5, 54 7.33 h or 10.44 h (single-peaked): 158 | |
| 0.100±0.025: 8 or 0.098±0.004: 2 (geometric) 0.039±0.005 (Bond): 23 | |
| Temperature | 65 K |
| B−V=0.69±0.02: 6 V−R=0.38±0.02 B−R=1.07±0.02 | |
| 20.5 | |
| 3.56±0.03: 62, 74 3.63±0.05: 8 3.62 | |
The surface of 2002 MS4 is dark gray and is composed of water and carbon dioxide ices. 2002 MS4 has been observed through stellar occultations, which have revealed massive topographic features along the outline of its shape. These features include a mountain-like peak that is 25 km (16 mi) tall and a crater-like depression that is 320 km (200 mi) wide and 45 km (28 mi) deep. 2002 MS4's topographic features are among the tallest and deepest known for Solar System bodies.