S/2010 (225088) 1

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
S/2010 (225088) 1
Moon Around the Dwarf Planet 2007 OR10.jpg
Hubble images of 2007 OR10 and its moon, taken in 2009 and 2010 with the Wide Field Camera 3[1]
Discovered byGábor Marton
Csaba Kiss
Thomas Müller[a]
Discovery date18 September 2010
(announced 17 October 2016)[a]
Orbital characteristics[5]
Epoch 8 December 2014 (JD 2457000.0)
24021±202 km (prograde), 24274±193 km (retrograde)
Eccentricity0.2908±0.007 (prograde), 0.2828±0.0063 (retrograde)
25.22073±0.000357 d (prograde), 25.22385±0.000362 d (retrograde)
Inclination83.08°±0.86° (prograde), 119.14°±0.89° (retrograde)
31.99°±1.07° (prograde), 104.09°±0.82° (retrograde)
Satellite of(225088) 2007 OR10
Physical characteristics
Mean diameter
< 100 km[b]
~237 km (assuming an albedo of 0.089)[7]
Albedo> 0.2
Spectral type

S/2010 (225088) 1 is the only known moon of scattered disc object and possible dwarf planet 2007 OR10, unofficially known as Gonggong. It was discovered by a team of astronomers led by Csaba Kiss during an analysis of archival Hubble Space Telescope images of 2007 OR10. The discovery team had suspected that the slow rotation of 2007 OR10 was caused by tidal forces exerted by an orbiting satellite.[4][3] The satellite was first identified in archival Hubble images taken with Hubble's Wide Field Camera 3 on 18 September 2010.[7] Its discovery was reported and announced by Gábor Marton, Csaba Kiss, and Thomas Müller at the 48th Meeting of the Division for Planetary Sciences on 17 October 2016,[4][2] and was subsequently assigned the provisional designation S/2010 (225088) 1.[8]


Hubble image sequence of 2007 OR10 and its satellite

Following the March 2016 discovery that 2007 OR10 was an unusually slow rotator, the possibility was raised that a satellite may have slowed it down via tidal forces.[4] The indications of a possible satellite orbiting 2007 OR10 led Csaba Kiss and his team to analyze archival Hubble observations of 2007 OR10.[7] Their analysis of Hubble images taken on 18 September 2010 revealed a faint satellite orbiting 2007 OR10 at a distance of at least 15,000 km (9,300 mi).[2] The discovery was announced on 17 October 2016 and the satellite was provisionally designated S/2010 (225088) 1.[8] The discovery team later also identified the satellite in earlier archival Hubble images taken on 9 November 2009.[7]

From follow-up Hubble observations in 2017, the absolute magnitude of the satellite is estimated to be at least 4.59 magnitudes dimmer than 2007 OR10, or 6.93±0.15 given the estimated absolute magnitude of 2.34 for the primary.[9][5]


Based on Hubble images of 2007 OR10 and its satellite taken in 2009 and 2010, the discovery team constrained the satellite's orbital period to between 20 and 100 days.[7] They better determined the orbit with additional Hubble observations in 2017.[9] The satellite is believed to be tidally locked to the primary.[5]

Because the observations of the satellite only span a small fraction of 2007 OR10's orbit around the Sun,[c] it is not yet possible to determine whether the orbit of the satellite is prograde or retrograde.[5] Based on a prograde orbit model, the satellite orbits the primary at a distance of around 24,021 km (14,926 mi) and completes one orbit in 25.22 days.[d] Using the same prograde orbit model, the discovery team has estimated that its orbit is inclined to the ecliptic by about 83 degrees, implying that 2007 OR10 is being viewed at a nearly pole-on configuration under the assumption that the satellite's orbit has a low inclination to the primary's equator.[5]

The orbit of S/2010 (225088) 1 is highly eccentric. The value of 0.29 is thought to have been caused by either an intrinsically eccentric orbit or by slow tidal evolution, in which the time for its orbit to circularize is comparable to the age of the Solar System.[5] It may have also resulted from the Kozai mechanism, driven by perturbations either from the Sun's tidal forces, or from higher order terms in the gravitational potential of 2007 OR10 due to its oblate shape.[5] The orbital dynamics are thought to be similar to that of Quaoar's satellite Weywot, which has a moderate eccentricity of about 0.14.[5]

Physical characteristics[edit]

In order for the satellite's orbit to remain eccentric over a timescale comparable to the age of the Solar System, it must be less than 100 km (62 mi) in diameter, corresponding to an albedo greater than 0.2.[5][b] Upon its discovery, the satellite's diameter was initially estimated at 237 km (147 mi), under the assumption that the albedos of the satellite and the primary were equal.[7] Photometric measurements in 2017 showed that the satellite is far less red than the primary.[5] The color difference of ΔV–I=0.43±0.17 between the primary (V–I=1.65±0.03) and satellite (V–I=1.22±0.17) is the largest among all known binary trans-Neptunian objects.[5] This large color difference is atypical for trans-Neptunian binary systems: the components of most trans-Neptunian binaries display little color variation, unlike the 2007 OR10 system.[5]


As of 2019, S/2010 (225088) 1 has not been named. When the discoverers of 2007 OR10 proposed choices for a public vote on its name, they chose figures that had associates that could provide a name for the satellite.[10]


  1. ^ a b The discoverers of S/2010 (225088) 1 began their analysis of archival Hubble images in 2016. The satellite was first identified in Hubble images taken on 18 September 2010, and was later reported and announced by Gábor Marton, Csaba Kiss, and Thomas Müller in the 48th Meeting of the Division for Planetary Sciences on 17 October 2016.[2][3][4]
  2. ^ a b The minimum diameter is 36 km (radius 18 km), corresponding to an albedo of 1.[6] The 100 km corresponds to an albedo of 0.2.[5]
  3. ^ Less than 10 years, compared to 2007 OR10's orbital period of 553 years.
  4. ^ The values in the retrograde model are similar.


  1. ^ "Moon Around the Dwarf Planet 2007 OR10". spacetelescope.org. Retrieved 22 May 2017.
  2. ^ a b c "The moon of the large Kuiper-belt object 2007 OR10" (PDF). DPS48 120.22. 2016. Retrieved 24 May 2019.
  3. ^ a b "Moon orbits third largest dwarf planet in our solar system". Science Daily. 18 May 2017. Retrieved 19 May 2017.
  4. ^ a b c d Lakdawalla, E. (19 October 2016). "DPS/EPSC update: 2007 OR10 has a moon!". The Planetary Society. Retrieved 19 October 2016.
  5. ^ a b c d e f g h i j k l m n o Kiss, Csaba; Marton, Gabor; Parker, Alex H.; Grundy, Will; Farkas-Takacs, Aniko; Stansberry, John; Pal, Andras; Muller, Thomas; Noll, Keith S.; Schwamb, Megan E.; Barr, Amy C.; Young, Leslie A.; Vinko, Jozsef (October 2018). "The mass and density of the dwarf planet (225088) 2007 OR10". Icarus. arXiv:1903.05439. Bibcode:2018DPS....5031102K. doi:10.1016/j.icarus.2019.03.013.
    Initial publication at the American Astronomical Society DPS meeting #50, with the publication ID 311.02
  6. ^ "Conversion of Absolute Magnitude to Diameter for Minor Planets". physics.sfasu.edu. Retrieved 14 May 2019.
  7. ^ a b c d e f Kiss, Csaba; Marton, Gábor; Farkas-Takács, Anikó; Stansberry, John; Müller, Thomas; Vinkó, József; Balog, Zoltán; Ortiz, Jose-Luis; Pál, András (16 March 2017). "Discovery of a Satellite of the Large Trans-Neptunian Object (225088) 2007 OR10". The Astrophysical Journal Letters. 838 (1): L1. Bibcode:2017ApJ...838L...1K. doi:10.3847/2041-8213/aa6484.
  8. ^ a b "Help Name 2007 OR10". Archived from the original on 25 May 2019. Retrieved 9 April 2019.
  9. ^ a b Parker, Alex (7 April 2017). "The Moons of Kuiper Belt Dwarf Planets Makemake and 2007 OR10 HST Proposal 15207". Mikulski Archive for Space Telescopes. Space Telescope Science Institute. Retrieved 21 September 2018.
  10. ^ "Astronomers Invite the Public to Help Name Kuiper Belt Object". International Astronomical Union. 10 April 2019. Retrieved 12 May 2019.