(

provisional designation Provisional designation in astronomy is the naming convention applied to astronomical objects immediately following their discovery. The provisional designation is usually superseded by a permanent designation once a reliable orbit has been calcu ...

) is a trans-Neptunian object and binary system that belongs to the scattered disc (like Eris). Its discovery was announced on 31 March 2014. It has an absolute magnitude (H) of 3.2. is a binary object, with two components approximately and in diameter. It is the ninth-intrinsically-brightest known trans-Neptunian object, and is approximately tied with and (to within measurement uncertainties) as the largest unnamed object in the Solar System.

Orbit

orbits the Sun once every 449 years. It will come to perihelion around November 2202, at a distance of about 35.6 AU. It is currently near aphelion, 80 AU from the Sun, and, as a result, it has an apparent magnitude of 22. Its orbit has a significant inclination of 33°. The

sednoid A sednoid is a trans-Neptunian object with a perihelion well beyond the Kuiper cliff at . Only four objects are known from this population: 90377 Sedna, , 541132 Leleākūhonua (), and , but it is suspected that there are many more. All four ha ...

and the scattered-disc object were discovered by the same survey as and were announced within about a week of one another.

Physical properties

has a diameter of about , 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. is one of the largest moderately red TNOs. The physical processes that lead to a lack of such moderately red TNOs larger than are not yet well understood. The brightness of varies by less than 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. Brown estimated, prior to the discovery of its satellite, that was very likely to be a dwarf planet, due to its large size. However, Grundy et al. calculate that bodies such as , 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.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 ()', ''Icarus'

doi: 10.1016/j.icarus.2018.12.037,

Satellite

Using Hubble Space Telescope observations taken in January 2018,

Scott Sheppard Scott Sander Sheppard (born 1977) is an American astronomer and a discoverer of numerous moons, comets and minor planets in the outer Solar System. He is an astronomer in the Department of Terrestrial Magnetism at the Carnegie Institution for Scie ...

found a satellite around , that was 0.17 arcseconds away and fainter than its primary. The discovery was announced on 10 August 2018. The satellite does not have a

nor a proper name. Assuming the two components have equal albedos, they are about and in diameter, respectively. Follow-up observations were taken between May and July 2018 in order to determine the orbit of the satellite, but the results of these observations remain yet to be published . Once the orbit is known, the mass of the system can be determined.

Notes

References

External links