1995 SN55
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(
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 The provisional designation is usually superseded by a permanent designation once a reliable orbit has been cal ...
) 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 ...
that orbits in the
outer Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...
beyond the orbit of Neptune. First observed as by
Spacewatch The Spacewatch Project is an astronomical survey that specializes in the study of minor planets, including various types of asteroids and comets at University of Arizona telescopes on Kitt Peak near Tucson, Arizona, in the United States. The Spa ...
on 20 September 1995, it was a
lost minor planet A minor planet is "lost" when today's observers cannot find it, because its location is too uncertain to target observations. This happens if the orbital elements of a minor planet are not known accurately enough, typically because the observat ...
with an insufficiently defined orbit with only 36 days of observations. On 8 October 2010, it was rediscovered by the
Pan-STARRS 1 The Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1; obs. code: F51 and Pan-STARRS2 obs. code: F52) located at Haleakala Observatory, Hawaii, US, consists of astronomical cameras, telescopes and a computing facility that is ...
survey and later announced as in July 2016. It was not until November 2020 when
amateur astronomer Amateur astronomy is a hobby where participants enjoy observing or imaging celestial objects in the sky using the unaided eye, binoculars, or telescopes. Even though scientific research may not be their primary goal, some amateur astronomers ...
s S. Deen and K. Ly identified and as the same object. This identification was confirmed and announced by the Minor Planet Center in January 2021. Once thought to be a centaur crossing the orbits of the
gas giant A gas giant is a giant planet composed mainly of hydrogen and helium. Gas giants are also called failed stars because they contain the same basic elements as a star. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" ...
s, is now known to be a trans-Neptunian object in a 3:5
orbital resonance In celestial mechanics, orbital resonance occurs when orbiting bodies exert regular, periodic gravitational influence on each other, usually because their orbital periods are related by a ratio of small integers. Most commonly, this relationsh ...
with Neptune. With an estimated diameter between , it was formerly considered one of the largest centaurs.


Observations


First observation and loss

was near
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 ...
35.4 Astronomical unit, AU from the Sun when it was first observed in 1995, by astronomers Nichole M. Danzl, Nichole Danzl and Arianna Gleason of the
Spacewatch The Spacewatch Project is an astronomical survey that specializes in the study of minor planets, including various types of asteroids and comets at University of Arizona telescopes on Kitt Peak near Tucson, Arizona, in the United States. The Spa ...
survey at Kitt Peak Observatory in Arizona, United States. It was only observed 14 times over 36 days, from 20 September to 26 October 1995. The discovery observations of were published and announced by the Minor Planet Center on 11 June 1999. By 2020 the 3-sigma uncertainty in the heliocentric distance to the original orbit solution for was approximately ±.


Recovery

On 30 November 2020, amateur astronomers S. Deen and K. Ly identified as the 3:5 resonant trans-Neptunian object , which was discovered by
Pan-STARRS 1 The Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1; obs. code: F51 and Pan-STARRS2 obs. code: F52) located at Haleakala Observatory, Hawaii, US, consists of astronomical cameras, telescopes and a computing facility that is ...
in 2010. The identification was published by the Minor Planet Center on 27 January 2021.


Classification and orbit

orbits the Sun at an average distance of 42.33 Astronomical unit, AU once every 275 years. Its orbit has an orbital eccentricity, eccentricity of 0.16 and an orbital inclination, inclination of 4Degree (angle), ° with respect to the ecliptic plane. Over the course of its orbit, its distance from the Sun ranges from 35.4 AU at
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 ...
to 49.3 AU at aphelion. is in a 3:5 orbital resonance, mean-motion orbital resonance with Neptune; for every three orbits it makes, Neptune orbits five times. Its orbit has a minimum orbit intersection distance approximately from Neptune's orbital path.


Numbering and naming

was Minor planet designation, numbered by the Minor Planet Center on 25 September 2018 and received the number in the LOMP, minor planet catalog. The alternate provisional designation in astronomy, provisional designation was given by the Minor Planet Center on 27 January 2021 after the two objects were linked. , it has not been List of named minor planets (numerical), named.


See also

* Lost minor planet * 1995 GJ – lost trans-Neptunian object * – misidentified nonexistent minor planet * – main-belt asteroid originally misidentified as a trans-Neptunian object


References


External links


A 300-kilometre space rock has vanished since we saw it in 1995
Joshua Sokol, ''New Scientist'', 25 October 2017 * {{DEFAULTSORT:2014 OK394 Trans-Neptunian objects in a 3:5 resonance, 523731 Minor planet object articles (numbered), 523731 Discoveries by Pan-STARRS, 523731 Astronomical objects discovered in 1995, 19950920 Astronomical objects discovered in 2010, 20101008