page_title: (55637) 2002 UX25
section_title: Satellite
hierarchical_section_title: (55637) 2002 UX25 / Satellite
caption_attribution_description: English: Simulated orbit of moon around 2002 UX, 210 km diameter moon with 4770 km orbital radius.
context_page_description: (55637) 2002 UX₂₅ is a Trans-Neptunian object that orbits the Sun in the Kuiper belt beyond Neptune. This TNO briefly garnered scientific attention when it was found to have an unexpectedly low density of about 0.82 g/cm³.
  (55637) 2002 UX has an absolute magnitude of about 4.0, and Spitzer Space Telescope results estimate it to be about 681 km in diameter.
  The low density of this - and many other mid sized TNO's - implies that they have likely never compressed into fully solid bodies, let alone differentiated or collapsed into hydrostatic equilibrium, and so are highly unlikely to be dwarf planets.
  It was discovered on 30 October 2002, by the Spacewatch program.
context_section_description: The discovery of a minor-planet moon was reported in IAUC 8812 on 22 February 2007. The satellite was detected using the Hubble Space Telescope in August 2005. The satellite was found at 0.16 arcsec from the primary with an apparent magnitude difference of 2.5. It orbits the primary in 8.309±0.0002 days, at a distance of 4770±40 km, yielding a system mass of (1.25±0.03)×10²⁰ kg. The eccentricity of the orbit is 0.17±0.03.
  This moon is estimated to be 210±30 km in diameter. Assuming the same albedo as the primary, it would have a diameter of 190 km, assuming an albedo of 0.05 (typical of other cold, classical KBOs of similar size) a diameter of 260 km.
caption: A simulated circular orbit of 210-km-diameter moon at a distance of 4770 km
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