(307261) 2002 MS4


(307261) 2002 MS4
2002MS4 Hubble.png
2002 MS4 imaged by the Hubble Space Telescope on 9 April 2006
Discovered byChadwick A. Trujillo
Michael E. Brown
Discovery sitePalomar Obs.
Discovery date18 June 2002
2002 MS4
TNO[2] · cubewano[3] · Scat-Ext[4]
Orbital characteristics[2]
Epoch 17 Dec 2020 (JD 2459200.5)
Uncertainty parameter 3
Observation arc24,188 days (66.22 yr)
Earliest precovery date8 April 1954
Aphelion47.925 AU
Perihelion36.141 AU
42.033 AU
272.52 yr (99,537 d)
0° 0m 13.02s / day
≈ 12 June 2123[5]
±14 days
Physical characteristics
Dimensions808±11 × 748±15 km RMS (projected)[6]
Mean diameter
800±24 km (2021)[7]
778±11 km (2020)[6]
770±2 km[8]
934±47 km (2012)[9]
726±123 km (2008, thermal)[10]
7.33 h or 10.44 h (single-peaked)[11]

(307261) 2002 MS4 is a large classical Kuiper belt object and a possible dwarf planet in the Kuiper belt, a region of icy planetesimals beyond Neptune.[3] It was discovered in 2002 by Chad Trujillo and Michael Brown, and has precovery images back to 8 April 1954.[2]

As of 2021, 2002 MS4 is 46.4 AU from the Sun.[13] It will reach perihelion, its closest point to the Sun, in 2123.[5] At 800 km (500 mi) in diameter, it is approximately tied with 2002 AW197 and 2013 FY27 (to within measurement uncertainties) as the largest unnamed object in the Solar System.


2002 MS4 was discovered using the Samuel Oschin telescope at Palomar Observatory

2002 MS4 was discovered on 18 June 2002 by Chad Trujillo and Michael Brown in their Caltech Wide Area Sky Survey conducted at Palomar Observatory.[14] The discovery was announced by the Minor Planet Center on 21 November 2002.[15]

In 2007, an archive search revealed the existence of several precovery observations of 2002 MS4, the earliest of which was taken on 8 April 1954, as part of the Digitized Sky Survey at Palomar Mountain.[16][2]

Orbit and classification

2002 MS4 is similar in orbit and current position to Quaoar, although with higher eccentricity and inclination, orbiting every 272.5 years. 2002 MS4 belongs to the class of dynamically hot Kuiper belt objects.[17] It is in an intermittent 18:11 orbital resonance with Neptune.[18]

The libration of 2002 MS4's nominal orbit, in a frame co-rotating with Neptune
The orbit of 2002 MS4 is similar to, but more inclined than, 50000 Quaoar's.


As of November 2019, 2002 MS4 has an observation arc of 66 years.[2]

EarthMoonCharonCharonNixNixKerberosStyxHydraHydraPlutoPlutoDysnomiaDysnomiaErisErisNamakaNamakaHi'iakaHi'iakaHaumeaHaumeaMakemakeMakemakeMK2MK2XiangliuXiangliuGonggongGonggongWeywotWeywotQuaoarQuaoarSednaSednaVanthVanthOrcusOrcusActaeaActaeaSalaciaSalacia2002 MS42002 MS4File:EightTNOs.png
Artistic comparison of Pluto, Eris, Haumea, Makemake, Gonggong, Quaoar, Sedna, Orcus, Salacia, 2002 MS4, and Earth along with the Moon

In 2008, the Spitzer Space Telescope estimated it to have a diameter of 726±123 km and the Herschel Space Telescope estimated it to be 934±47 km.[10]

Seven occultation events were observed from 2019 to 2021. The most successful was on 08 August 2020, involving 116 telescopes. The result was a diameter of 800±24 km; the ±24-km variation is thought to be largely due to surface features.[7]

2002 MS4 has measured color indices of B−V=0.69±0.02 and V−R=0.38±0.02, which indicates that it has a neutral (gray) surface color.[12] Per Barucci et al.'s classification scheme for TNO color indices, 2002 MS4 falls under the BB group of TNOs with neutral colors.[19]

New Horizons

In July 2016, 2002 MS4 was observed by the New Horizons spacecraft, as part of its extended Kuiper belt mission. The observations significantly improved the knowledge of 2002 MS4's orbit and phase curve.[20][21]

2002 MS4, imaged by the New Horizons spacecraft in July 2016, from a distance of 15.3 AU


2002 MS4's position in Scutum, moving eastward across the brightest areas of the Milky Way

2002 MS4 passes through the Milky Way sky of the constellation Scutum with 7 stellar occultations predicted between 2019 and 2021.

Two stellar occultations by 2002 MS4 were observed from South America and Canada on 9 July and 26 July 2019, both yielding at least two positive detections from participating observers. A negative chord grazing the projected shape of 2002 MS4 on the 9 July event allowed for constraints on its diameter, yielding a best-fit equivalent spherical radius of 770±2 km.[8] In the following month, two observers from Canada recorded another stellar occultation by 2002 MS4 on 19 August 2019. The two positive chords from the event suggested that 2002 MS4 may have an oblate shape, with projected dimensions of 842 × 688 km.[22]

On 8 August 2020, a campaign organized by Lucky Star project successfully observed the occultation of a magnitude 14.6 star with 22 positive detections.[23][24][this contradicts the report in the Sept 2021 meeting, which shows 45–60 cords] The resulting projected dimensions of 2002 MS4 were 808 × 748 km, consistent with the results from the previous year.[6] Topographic features 20 km (12 mi) in depth and height were observed on 2002 MS4's surface.[7]


As of 2019, the rotation period of 2002 MS4 is unknown. Observations in 2005 and 2011 showed possible periods of either 7.33 hours or its alias 10.44 hours (single-peaked), or twice those values for the double-peaked solution, with a small light curve amplitude of 0.05±0.01 mag. Light curve observations of 2002 MS4 are difficult because of the dense field of background stars it is crossing. Observations made in June and July 2011 took advantage of 2002 MS4 moving in front of a dark nebula.[11]

No known moons

2002 MS4 does not have any known moons orbiting it, thus an accurate mass estimate cannot be made. Based on its size alone, Brown lists it as nearly certain to be a dwarf planet.[25] However, its low albedo may imply the opposite: dark, mid-sized bodies such as this, less than about 900–1000 km in diameter and with albedos less than about 0.2 that suggest they have never been resurfaced, have likely never collapsed into solid bodies, much less differentiated or relaxed into hydrostatic equilibrium, and thus are unlikely to be dwarf planets.[26]

See also



  1. ^ a b "(307261) = 2002 MS4". Minor Planet Center. International Astronomical Union. Retrieved 13 September 2021.
  2. ^ a b c d e f "JPL Small-Body Database Browser: 307261 (2002 MS4)" (2020-06-28 last obs.). Jet Propulsion Laboratory. Archived from the original on 30 June 2021. Retrieved 13 September 2021.
  3. ^ a b "MPEC 2009-P26 :Distant Minor Planets (2009 AUG. 17.0 TT)". IAU Minor Planet Center. 7 August 2009. Retrieved 31 August 2009.
  4. ^ Buie, M. W. "Orbit Fit and Astrometric record for 307261". Southwest Research Institute. Archived from the original on 4 June 2011. Retrieved 13 September 2021.
  5. ^ a b JPL Horizons (Perihelion occurs when deldot changes from negative to positive. Uncertainty in time of perihelion is 3-sigma.)
  6. ^ a b c "2020/08/08 - 307261 - 2002 MS4 - 4UC419-096262". euraster.net. Euraster. 16 August 2020. Retrieved 31 August 2020.
  7. ^ a b c Rommel, Flavia L.; Braga-Ribas, Felipe; Vara-Lubiano, Mónica; Ortiz, Jose L.; Desmars, Josselin; Morgado, Bruno E.; et al. (September 2021). Evidence of topographic features on (307261) 2002 MS4 surface. Europlanet Science Congress 2021. Europlanet Society. doi:10.5194/epsc2021-440. EPSC2021-440. Retrieved 13 September 2021.
  8. ^ a b c Rommel, Flavia Luane; Braga-Ribas, Felipe; Pereira, Crystian Luciano; Desmars, Josselin; Santos-Sanz, Pablo; Benedetti-Rossi Rossi, Gustavo; et al. (September 2020). Results on stellar occultations by (307261) 2002 MS4. Europlanet Science Congress 2020. Europlanet Society. Bibcode:2020EPSC...14..866L. doi:10.5194/epsc2020-866. EPSC2020-866. Retrieved 6 September 2021.
  9. ^ a b c Vilenius, E.; Kiss, C.; Mommert, M.; Müller, T.; Santos-Sanz, P.; Pal, A.; et al. (May 2012). ""TNOs are Cool": A survey of the trans-Neptunian region VI. Herschel/PACS observations and thermal modeling of 19 classical Kuiper belt objects" (PDF). Astronomy & Astrophysics. 541: 17. arXiv:1204.0697. Bibcode:2012A&A...541A..94V. doi:10.1051/0004-6361/201118743. S2CID 54222700. A94.
  10. ^ a b Stansberry, John; Grundy, Will; Brown, Mike; Cruikshank, Dale; Spencer, John; Trilling, David; Margot, Jean-Luc (2008). "Physical Properties of Kuiper Belt and Centaur Objects: Constraints from the Spitzer Space Telescope" (PDF). The Solar System Beyond Neptune. University of Arizona Press. pp. 161–179. arXiv:astro-ph/0702538. Bibcode:2008ssbn.book..161S. ISBN 9780816527557.
  11. ^ a b Thirouin, Audrey (2013). Study of Trans-Neptunian Objects using photometric techniques and numerical simulations (PDF) (Thesis). University of Granada. pp. 92–95. S2CID 125259956. Retrieved 19 November 2019.
  12. ^ a b Tegler, S. C.; Romanishin, W.; Consolmagno, G. J. (December 2016). "Two Color Populations of Kuiper Belt and Centaur Objects and the Smaller Orbital Inclinations of Red Centaur Objects". The Astronomical Journal. 152 (6): 13. Bibcode:2016AJ....152..210T. doi:10.3847/0004-6256/152/6/210. S2CID 125183388. 210.
  13. ^ a b "(307261) 2002MS4 Ephemerides". Asteroids Dynamic Site. Department of Mathematics, University of Pisa, Italy. Retrieved 19 November 2019.
  14. ^ Trujillo, C. A.; Brown, M. E. (June 2003). "The Caltech Wide Area Sky Survey". Earth, Moon, and Planets. 92 (1): 99–112. Bibcode:2003EM&P...92...99T. doi:10.1023/B:MOON.0000031929.19729.a1. S2CID 189905639.
  15. ^ "MPEC 2002-W27 : 2002 MS4, 2002 QX47, 2002 VR128". Minor Planet Electronic Circular. Minor Planet Center. 21 November 2002. Retrieved 26 August 2009.
  16. ^ Minor Planets and Comets Supplement (PDF), Minor Planet Center, 30 December 2007, p. 231732, retrieved 19 November 2019
  17. ^ Treatise on Geophysics. 1 (2 ed.). Elsevier. 2015. p. 643. ISBN 9780444538031. Retrieved 19 November 2019.
  18. ^ Lykawka, Patryk Sofia; Tadashi, Mukai (July 2007). "Dynamical classification of trans-neptunian objects: Probing their origin, evolution, and interrelation" (PDF). Icarus. 189 (1): 213–232. Bibcode:2007Icar..189..213L. doi:10.1016/j.icarus.2007.01.001. S2CID 122671996.
  19. ^ Barucci, M. A.; Belskaya, I.; Fulchignoni, M.; Birlan, M. (September 2005). "Taxonomy of Centaurs and Trans-Neptunian Objects". The Astronomical Journal. 130 (3): 1291–1298. Bibcode:2005AJ....130.1291B. doi:10.1086/431957. S2CID 32008426.
  20. ^ Lakdawalla, E. (24 January 2018). "New Horizons prepares for encounter with 2014 MU69". The Planetary Society. Retrieved 13 November 2019.
  21. ^ Verbiscer, A.; Porter, S.; Spencer, J.R.; Buie, M.W.; et al. (2017), "New Horizons High-Phase Observations of Distant Kuiper Belt Objects", AGU Fall Meeting Abstracts, 2017: P11C–2528, Bibcode:2017AGUFM.P11C2528V
  22. ^ "(307261) 2002 MS4, 2019 Aug 19 occultation". IOTA Asteroid Occultation Results Webpage. International Occultation Timing Association. 19 August 2019. Retrieved 19 November 2019.
  23. ^ "2002 MS4 08/08/2020". ERC Lucky Star project. Retrieved 6 September 2021.
  24. ^ Masi, Gianluca (17 August 2020). "Trans-Neptunian object (307261) 2002 MS4 occulted UCAC4 419-096262: a very precious event – 8 Aug. 2020". The Virtual Telescope Project 2.0. Retrieved 6 September 2021.
  25. ^ Brown, Michael E. (23 February 2021). "How many dwarf planets are there in the outer solar system?". California Institute of Technology. Retrieved 13 September 2021.
  26. ^ Grundy, W. M.; Noll, K. S.; Buie, M. W.; Benecchi, S. D.; Ragozzine, D.; Roe, H. G. (December 2019). "The Mutual Orbit, Mass, and Density of Transneptunian Binary Gǃkúnǁʼhòmdímà ((229762) 2007 UK126)". Icarus. 334: 30–38. Bibcode:2019Icar..334...30G. doi:10.1016/j.icarus.2018.12.037. S2CID 126574999.

External links

  • 2002 MS4 Precovery Images
  • (307261) 2002 MS4
  • (307261) 2002 MS4 at the JPL Small-Body Database
    • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters