1998 SN165 orbits the Sun at a distance of 36.5–39.7 AU once every 234 years and 9 months (85,755 days; semi-major axis of 38.06 AU). Its orbit has an eccentricity of 0.04 and an inclination of 5° with respect to the ecliptic.[2] As of 2021[update] the object is at 37.2 AU,[14] approaching the Sun until 15 July 2065, when it will come to perihelion.[a] The body's observation arc begins at Kitt Peak in September 1998, just eight nights prior to its official discovery observation.[1]
As a cubewano, also known as classical Kuiper belt object,[4]1998 SN165 is located in between the resonant plutino and twotino populations and has a low-eccentricity orbit. It belongs to the cold population, distinct from the "stirred" hot population with inclinations higher than 5°. In a previous publication, the object was originally classified as a plutino.[15]
1998 SN165 has a blue-grey color (BB),[10] with various color indices measured,[7][13] giving a difference between the blue and red filter magnitude (BR) of 1.123 and 1.13, respectively.[3][11][12]
Rotation period
In February 2001, a rotational lightcurve of 1998 SN165 was obtained from photometric observations by Pedro Lacerda and Jane Luu. Lightcurve analysis gave an ambiguous rotation period of 8.84 hours with a brightness amplitude of 0.16 magnitude (U=2). An alternative period of 8.70 hours is also possible.[9][13]
Diameter and albedo
According to observations by the space-based Herschel and Spitzer telescopes, 1998 SN165 measures between 393 and 460 kilometers and its surface has a low albedo between 0.043 and 0.060.[6][7][8] While Johnston's Archive adopts a diameter of 393 kilometers, astronomer Michael Brown gives a radiometric diameter of 473 kilometers and lists this object as a "probable" dwarf planet (400–500 km), which is the category with the second lowest certainty in his 5-class taxonomic system.[5] The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.10 and calculates a diameter of 334 kilometers based on an absolute magnitude of 5.5.[13] A generic magnitude-to-diameter conversion with an albedo of 0.9 gives a diameter of 352 kilometers.[18]
Notes
^ abJPL Horizons Observer Location: @sun (Perihelion occurs when deldot changes from negative to positive. Uncertainty in time of perihelion is 3-sigma, ±9 days.)
^ abcVilenius, E.; Kiss, C.; Müller, T.; Mommert, M.; Santos-Sanz, P.; Pál, A.; et al. (April 2014). ""TNOs are Cool": A survey of the trans-Neptunian region. X. Analysis of classical Kuiper belt objects from Herschel and Spitzer observations". Astronomy and Astrophysics. 564: 18. arXiv:1403.6309. Bibcode:2014A&A...564A..35V. doi:10.1051/0004-6361/201322416. S2CID118513049.
^ abcStansberry, John; Grundy, Will; Brown, Michael E.; Cruikshank, Dale; Spencer, John; Trilling, David; Margot, Jean-Luc (2008). "Physical Properties of Kuiper Belt and Centaur Objects: Constraints from Spitzer Space Telescope". In M. Antonietta Barucci; Hermann Boehnhardt; Dale P. Cruikshank; Alessandro Morbidelli (eds.). The Solar System beyond Neptune. University of Arizona Press. arXiv:astro-ph/0702538. Bibcode:2008ssbn.book..161S.