(

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 The provisional designation is usually superseded by a permanent designation once a reliable orbit has been calc ...

) is a

trans-Neptunian object A trans-Neptunian object (TNO), also written transneptunian object, is any minor planet in the Solar System that orbits the Sun at a greater average distance than Neptune, which has a semi-major axis of 30.1 astronomical units (au). Typically ...

and

binary system A binary system is a system of two astronomical bodies which are close enough that their gravitational attraction causes them to orbit each other around a barycenter ''(also see animated examples)''. More restrictive definitions require that th ...

that belongs to the

scattered disc The scattered disc (or scattered disk) is a distant circumstellar disc in the Solar System that is sparsely populated by icy small solar system bodies, which are a subset of the broader family of trans-Neptunian objects. The scattered-disc obje ...

(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 An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any elli ...

around November 2202, at a distance of about 35.6 AU. It is currently near

aphelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ell ...

, 80 AU from the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

, and, as a result, it has an

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...

of 22. Its orbit has a significant inclination of 33°. The sednoid 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 The Atacama Large Millimeter/submillimeter Array (ALMA) is an astronomical interferometer of 66 radio telescopes in the Atacama Desert of northern Chile, which observe electromagnetic radiation at millimeter and submillimeter wavelengths. The ...

and

Magellan Telescopes The Magellan Telescopes are a pair of optical telescopes located at Las Campanas Observatory in Chile. The two telescopes are named after the astronomer Walter Baade and the philanthropist Landon T. Clay. First light for the telescopes was on ...

, its

albedo Albedo (; ) is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body that refle ...

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 The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most vers ...

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 A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioiso ...

around , that was 0.17

arcseconds A minute of arc, arcminute (arcmin), arc minute, or minute arc, denoted by the symbol , is a unit of angular measurement equal to of one degree. Since one degree is of a turn (or complete rotation), one minute of arc is of a turn. The ...

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