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2013 FY27, also written 2013 FY27, is a trans-Neptunian object and binary system that belongs to the scattered disc (like Eris).[9] Its discovery was announced on 31 March 2014.[1] It has an absolute magnitude (H) of 3.0.[6] 2013 FY27 is a binary object, with two components approximately 740 kilometres (460 mi) and 190 kilometres (120 mi) in diameter. It is the ninth-intrinsically-brightest known trans-Neptunian object,[10] and is the largest unnumbered minor planet as of September 2018.

2013 FY27
2013 FY27.png
2013 FY27 and its satellite, imaged by the Hubble Space Telescope on 15 January 2018
Discovered byScott Sheppard
Chad Trujillo
Discovery date17 March 2013
announced: 31 March 2014
MPC designation2013 FY27
Orbital characteristics[6]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 7
Observation arc1852 days (5.07 yr)
Aphelion82.0857 AU (12.27985 Tm)
Perihelion35.7151 AU (5.34290 Tm)
58.9004 AU (8.81137 Tm)
452.05 yr (165034 d)
213.3220° (M)
0° 0m 7.849s /day
Known satellites1 [3][4][5]
Physical characteristics
Mean diameter
(primary), 190 km (secondary)[a][3]
780 km (Brown)[7]
530[b]–1100[c] km[6][8]
900 km[9]
0.15 (theoretically expected value)[7]
moderately red
V-R=0.56±0.03, R-I=0.52±0.03[3]
3.0 (JPL/MPC)[6]
3.3 (Brown)[7]
3.15±0.03 (Sheppard)[3]



Orbit of 2013 FY27

2013 FY27 orbits the Sun once every 452 years. It will come to perihelion around 2202,[d] at a distance of about 36 AU.[6] It is currently near aphelion, 80 AU from the Sun, and, as a result, it has an apparent magnitude of 22.[1] Its orbit has a significant inclination of 33°.[6] The sednoid 2012 VP113 and the scattered-disc object 2013 FZ27 were discovered by the same survey as 2013 FY27 and were announced within about a week of one another.

Physical propertiesEdit

2013 FY27 has a diameter of about 740 kilometres (460 mi), placing it at a transition zone between medium-sized and large TNOs. Using the Atacama Large Millimeter Array and Magellan Telescopes, its albedo was found to be 0.17, and its colour to be moderately red. 2013 FY27 is one of the largest moderately red TNOs. The physical processes that lead to a lack of such moderately red TNOs larger than 800 kilometres (500 mi) are not yet well understood.

The brightness of 2013 FY27 varies by less than 0.06 mag over hours and days, suggesting that it either has a very long rotation period, an approximately spheroidal shape, or a rotation axis pointing towards Earth.[3]

Brown estimates that 2013 FY27 is very likely to be a dwarf planet, due to its large size.[7] However, Grundy et al. calculate that bodies such as 2013 FY27, less than about 1000 km in diameter, with albedos less than ≈0.2 and densities of ≈1.2 g/cm3 or less, may retain a degree of porosity in their physical structure, having never collapsed into fully solid bodies.[11]


Using Hubble Space Telescope observations taken in January 2018, Scott Sheppard found a satellite around 2013 FY27, 0.17 arcseconds away and 3.0±0.2 mag fainter than the primary. The discovery was announced on 10 August 2018.[12] Assuming the two components have equal albedos, they are about 740 kilometres (460 mi) and 190 kilometres (120 mi) in size, respectively.[3] Follow up observations have been taken between May and July 2018 in order to determine the orbit of the satellite,[4] but the results of those observations have not yet been released. Once the orbit is known, the masses and densities of the two components can be determined.

See alsoEdit


  1. ^ Assuming the two components have equal albedos
  2. ^ Assuming an albedo of 0.4
  3. ^ Assuming an albedo of 0.1
  4. ^ The uncertainty in the year of perihelion passage is ≈2.5 years.[6]


  1. ^ a b c "MPEC 2014-F82 : 2013 FY27". IAU Minor Planet Center. 2014-03-31. Retrieved 2018-03-29. (K13F27Y)
  2. ^ "List Of Centaurs and Scattered-Disk Objects". Minor Planet Center. Retrieved 2014-04-02.
  3. ^ a b c d e f g Sheppard, Scott; Fernandez, Yanga; Moullet, Arielle (6 September 2018). "The Albedos, Sizes, Colors and Satellites of Dwarf Planets Compared with Newly Measured Dwarf Planet 2013 FY27". arXiv:1809.02184. Retrieved 9 September 2018.
  4. ^ a b Scott Sheppard (21 March 2018). "The Orbit of the Newly Discovered Satellite around the Dwarf Planet 2013 FY27 - HST Proposal 15460". Retrieved 9 September 2018.
  5. ^ Scott Sheppard (7 April 2017). "A Satellite Search of a Newly Discovered Dwarf Planet - HST Proposal 15248". Retrieved 9 September 2018.
  6. ^ a b c d e f g "JPL Small-Body Database Browser: (2013 FY27)" (last observation: 2018-04-12; arc: 5.07 years). Jet Propulsion Laboratory. Retrieved 9 September 2018.
  7. ^ a b c d Mike Brown, How many dwarf planets are there in the outer solar system? Archived 18 October 2011 at the Wayback Machine (assumes H = 3.3)
  8. ^ Dan Bruton. "Conversion of Absolute Magnitude to Diameter for Minor Planets". Department of Physics & Astronomy (Stephen F. Austin State University). Archived from the original on 2011-07-23. Retrieved 2014-03-26.
  9. ^ a b Lakdawalla, Emily (2014-04-02). "More excitement in the outermost solar system: 2013 FY27, a new dwarf planet". The Planetary Society. Retrieved 18 January 2017.
  10. ^ "JPL Small-Body Database Search Engine: orbital class (TNO) and H < 3.1 (mag)". JPL Solar System Dynamics. Retrieved 2014-03-31.
  11. ^ W.M. Grundy, K.S. Noll, M.W. Buie, S.D. Benecchi, D. Ragozzine & H.G. Roe, 'The Mutual Orbit, Mass, and Density of Transneptunian Binary Gǃkúnǁʼhòmdímà ((229762) 2007 UK126)', Icarus [1] doi: 10.1016/j.icarus.2018.12.037,
  12. ^ "CBET 4537: 2013 FY27". 10 August 2018. Retrieved 9 September 2018.

External linksEdit