(153591) 2001 SN263

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(153591) 2001 SN263
Discovery [1]
Discovered by LINEAR
Discovery site Lincoln Lab's ETS
Discovery date 20 September 2001
MPC designation (153591) 2001 SN263
2001 SN263
NEO · Amor[1][2]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc 25.18 yr (9,198 days)
Aphelion 2.9368 AU
Perihelion 1.0363 AU
1.9865 AU
Eccentricity 0.4783
2.80 yr (1,023 days)
0° 21m 7.2s / day
Inclination 6.6853°
Known satellites 2[3]
Earth MOID 0.0520 AU · 20.3 LD
Physical characteristics
Mean diameter
2 km[3]
2.5±0.3 km[4]
2.6 km[5]
2.63±0.40 km[6]
Mass (917.5±2.2)×1010 kg[7]
Mean density
1.1±0.2 g/cm³[4]
3.20±0.01 h[8]
3.423±0.001 h[a]
3.42510±0.00007 h[9]
3.4256±0.0002 h[4]
C[8] · B[b]
16.81[10] · 16.9[1]

(153591) 2001 SN263 is a carbonaceous trinary[3] asteroid, classified as near-Earth object and former potentially hazardous asteroid of the Amor group, approximately 2.6 kilometers in diameter.

It was discovered by the Lincoln Near-Earth Asteroid Research project at Lincoln Lab's Experimental Test Site in Socorro, New Mexico, on 20 September 2001.[2]

The two synchronous minor-planet moons measure approximately 770 and 430 meters and have an orbital period of 16.46 and 150 hours, respectively.[4][10]


2001 SN263, the primary object of this trinary system, is an unusual carbonaceous near-Earth asteroid of a C- or somewhat brighter B-type.[8][b] It orbits the Sun at a distance of 1.0–2.9 AU once every 2 years and 10 months (1,023 days). Its orbit has an eccentricity of 0.48 and an inclination of 7° with respect to the ecliptic.[1] A first precovery was taken at Palomar Observatory during the Digitized Sky Survey in 1990, extending the body's observation arc by 11 years prior to its official discovery observation at Socorro.[2]

It has an Earth minimum orbital intersection distance (MOID) of 0.0520 AU (7,780,000 km), which translates into 20.3 lunar distances.[1] With an Earth MOID above 0.05 AU, 2001 SN263 is no longer a potentially hazardous asteroid, but it was classified as such by the MPC until early 2017.[2][11]

Radar observations show that it measures 2.5 kilometers in diameter.[4] Its surface has a low albedo of 0.048.[6] Rotational lightcurves obtained from photometric observations gave a rotation period of 3.423 hours (best result) with a brightness variation between 0.13 and 0.27 magnitude (U=2/3/3).[8][9][a] Radar observations gave a concurring period of 3.4256 hours, and subsequent modeling of both radiometric and photometric observations gave a spin axis of (309.0°, −80.0°) in ecliptic coordinates (λ, β).[4]

Trinary system[edit]

In 2008, scientists using the planetary radar at Arecibo Observatory discovered that the object is orbited by two satellites, when the triple asteroid made a close approach to Earth of 0.066 AU (nearly 10 million kilometers). The largest body (preliminarily called Alpha) is spheroid in shape, with principal axes of 2.8±0.1 km, 2.7±0.1 km, and 2.9±0.3 km, with an effective diameter of 2.5±0.3 km and a density of 1.1±0.2 g/cm3. The satellites, named Beta and Gamma, are several times smaller in size. Beta is 0.77±0.12 km in diameter and Gamma 0.43±0.14 km.[4]

The only other unambiguously identified triple asteroids in the near-Earth population are (136617) 1994 CC, which was discovered to be a triple system in 2009, and 3122 Florence, which was found to be a triple system in September 2017.[12]

Orbital characteristics of satellites[edit]

The orbital properties of the satellites are listed in this table.[7] The orbital planes of both satellites are inclined relative to each other; the relative inclination is about 14 degrees. Such a large inclination is suggestive of past evolutionary events (e.g. close encounter with a terrestrial planet, mean-motion-resonance crossing) that may have excited their orbits from a coplanar configuration to an inclined state.

Name Mass Semi-major axis Orbital period Eccentricity
Gamma (inner) ~10×1010 kg 3.8 km 0.686 days 0.016
Beta (outer) ~24×1010 kg 16.6 km 6.225 days 0.015

Numbering and naming[edit]

This minor planet was numbered by the Minor Planet Center on 2 April 2007.[13] As of 2018, the primary and its moons have not been named.[2] In the scientific literature, the components of the trinary system are generically referred to as Alpha, Beta and Gamma, but these labels are not recognized by the IAU.[5][4]


  1. ^ a b Warner (2011) web: lightcurve plot of (153591) 2001 SN263, Palmer Divide Observatory, Brian D. Warner (2008). Photometric observations from 20 February 2008: rotation period 3.423±0.001 hours with a brightness amplitude of 0.14±0.02 magnitude. Quality code: 3. Summary figures for all obtained lightcurves at Collaborative Asteroid Lightcurve Link (CALL) for (153591)
  2. ^ a b Perna (2014): photometric observation from 24 June 2011: with a brightness amplitude of mag. Summary figures at Collaborative Asteroid Lightcurve Link (CALL) for (153591)


  1. ^ a b c d e f "JPL Small-Body Database Browser: 153591 (2001 SN263)" (2015-12-01 last obs.). Jet Propulsion Laboratory. Retrieved 1 June 2017. 
  2. ^ a b c d e "153591 (2001 SN263)". Minor Planet Center. Retrieved 3 September 2017. 
  3. ^ a b c Nolan, M. C.; Howell, E. S.; Benner, L. A. M.; Ostro, S. J.; Giorgini, J. D.; Busch, M. W.; et al. (February 2008). "(153591) 2001 SN_263". Central Bureau Electronic Telegrams (1254). Bibcode:2008CBET.1254....1N. Retrieved 22 March 2017. 
  4. ^ a b c d e f g h Becker, Tracy M.; Howell, Ellen S.; Nolan, Michael C.; Magri, Christopher; Pravec, Petr; Taylor, Patrick A.; et al. (March 2015). "Physical modeling of triple near-Earth Asteroid (153591) 2001 SN263 from radar and optical light curve observations". Icarus. 248: 499–515. Bibcode:2015Icar..248..499B. doi:10.1016/j.icarus.2014.10.048. Retrieved 22 March 2017. 
  5. ^ a b Becker, Tracy; Howell, E. S.; Nolan, M. C.; Magri, C. (September 2008). "Physical Modeling of Triple Near-Earth Asteroid 153591 (2001 SN263)". American Astronomical Society. 40: 437. Bibcode:2008DPS....40.2806B. Retrieved 22 March 2017. 
  6. ^ a b c Delbo, Marco; Walsh, Kevin; Mueller, Michael; Harris, Alan W.; Howell, Ellen S. (March 2011). "The cool surfaces of binary near-Earth asteroids". Icarus. 212 (1): 138–148. Bibcode:2011Icar..212..138D. doi:10.1016/j.icarus.2010.12.011. Retrieved 22 March 2017. 
  7. ^ a b Fang, Julia; Margot, Jean-Luc; Brozovic, Marina; Nolan, Michael C.; Benner, Lance A. M.; Taylor, Patrick A. (May 2011). "Orbits of Near-Earth Asteroid Triples 2001 SN263 and 1994 CC: Properties, Origin, and Evolution". The Astronomical Journal. 141 (5): 15. arXiv:1012.2154Freely accessible. Bibcode:2011AJ....141..154F. doi:10.1088/0004-6256/141/5/154. Retrieved 1 June 2017. 
  8. ^ a b c d Betzler, Alberto Silva; Novaes, Alberto Brum; Celedon, Julian Hermogenes Quesada (October 2008). "A Study of the Trinary NEA 2001 SN263". The Minor Planet Bulletin. 35 (4): 182–184. Bibcode:2008MPBu...35..182B. ISSN 1052-8091. Retrieved 22 March 2017. 
  9. ^ a b Oey, Julian (January 2009). "Lightcurve Analysis of Asteroids from Leura and Kingsgrove Observatories in the First Half of 2008". The Minor Planet Bulletin. 36 (1): 4–6. Bibcode:2009MPBu...36....4O. ISSN 1052-8091. Retrieved 22 March 2017. 
  10. ^ a b "LCDB Data for (153591)". Asteroid Lightcurve Database (LCDB). Retrieved 3 September 2017. 
  11. ^ "153591 (2001 SN263)". Minor Planet Center. web.archive.org. 22 March 2017. Archived from the original on 22 March 2017. Retrieved 3 September 2017. 
  12. ^ "Radar Reveals Two Moons Orbiting Asteroid Florence". Jet Propulsion Laboratory. September 1, 2017. 
  13. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 24 February 2018. 

External links[edit]