7066 Nessus is a very red

centaur A centaur ( ; ; ), occasionally hippocentaur, also called Ixionidae (), is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse that was said to live in the mountains of Thessaly. In one version o ...

on an eccentric orbit, located beyond

Saturn Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...

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 "Sol ...

. It was discovered on 26 April 1993, by astronomers 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. The Spacewatch Project has be ...

program at the

Kitt Peak National Observatory The Kitt Peak National Observatory (KPNO) is a United States astronomy, astronomical observatory located on Kitt Peak of the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono Oʼodham Nation, west-southwest of Tucson, Arizona. With ...

Tucson, Arizona Tucson (; ; ) is a city in Pima County, Arizona, United States, and its county seat. It is the second-most populous city in Arizona, behind Phoenix, Arizona, Phoenix, with a population of 542,630 in the 2020 United States census. The Tucson ...

. The dark and reddish

minor planet According to the International Astronomical Union (IAU), a minor planet is an astronomical object in direct orbit around the Sun that is exclusively classified as neither a planet nor a comet. Before 2006, the IAU officially used the term ''minor ...

is likely elongated and measures approximately in diameter. It was named after Nessus from Greek mythology.

Orbit and classification

Nessus is a

, a dynamically unstable population of

s between the classical

asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...

s and the

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 an orbital semi-major axis of 30.1 astronomical units (AU). ...

s. It orbits the Sun at a distance of 11.9–37.4 AU once every 122 years and 4 months (44,670 days;

semi-major axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the longe ...

of 24.64 AU). Its orbit has an

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...

of 0.52 and an

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

of 16 ° with respect to the

ecliptic The ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making. Fr ...

. At its

perihelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

(11.9 AU), it moves much closer to the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

than

Uranus Uranus is the seventh planet from the Sun. It is a gaseous cyan-coloured ice giant. Most of the planet is made of water, ammonia, and methane in a Supercritical fluid, supercritical phase of matter, which astronomy calls "ice" or Volatile ( ...

(19.2 AU) but not as close as Saturn (9.6 AU), while at its

aphelion An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

(37.4 AU), it moves out well beyond the orbit of

Neptune Neptune is the eighth and farthest known planet from the Sun. It is the List of Solar System objects by size, fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 t ...

(30.1 AU). The orbits of centaurs are unstable due to perturbations by the

giant planet A giant planet, sometimes referred to as a jovian planet (''Jove'' being another name for the Roman god Jupiter (mythology), Jupiter), is a diverse type of planet much larger than Earth. Giant planets are usually primarily composed of low-boiling ...

s. Nessus is an "SE object" because currently Saturn controls its perihelion and its aphelion is within the

Kuiper belt The Kuiper belt ( ) is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times ...

. It is estimated to have a relatively long orbital half-life of about 4.9 million years. Fifty clones of the orbit of Nessus suggest that it will not pass within 1 AU (or 150 million kilometers) of any planet for at least 20,000 years.

Discovery and naming

Nessus was discovered by

David Rabinowitz David Lincoln Rabinowitz (born 1960) is an American astronomer, discoverer of minor planets and researcher at Yale University. Career David Rabinowitz has built CCD cameras and software for the detection of near-Earth and Kuiper belt obje ...

(not officially credited), working with the

program, at

on 26 April 1993. The discovery was announced on 13 May 1993 in an ''

IAU Circular The International Astronomical Union Circulars (IAUCs) are notices that give information about astronomical phenomena. IAUCs are issued by the International Astronomical Union's Central Bureau for Astronomical Telegrams (CBAT) at irregular interva ...

'' (IAUC 5789) of the

Central Bureau for Astronomical Telegrams The Central Bureau for Astronomical Telegrams (CBAT) is an official international clearing house for information relating to transient astronomical events. The CBAT collects and distributes information on comets, natural satellites, novae, mete ...

. It was the third discovery of a centaur after

2060 Chiron 2060 Chiron is a ringed small Solar System body in the outer Solar System, orbiting the Sun between Saturn and Uranus. Discovered in 1977 by Charles Kowal, it was the first-identified member of a new class of objects now known as centaurs— ...

and

5145 Pholus 5145 Pholus is an eccentric centaur (minor planet), centaur in the outer Solar System, approximately in diameter, that crosses the orbit of both Saturn and Neptune. It was discovered on 9 January 1992 by American astronomer David Rabinowitz (u ...

, discovered by Charles Kowal and David Rabinowitz in 1977 and 1992, respectively. The body's

observation arc In observational astronomy, the observation arc (or arc length) of a Solar System body is the time period between its earliest and latest observations, used for tracing the body's path. It is usually given in days or years. The term is mostly use ...

begins with its official discovery observation at

Kitt Peak Kitt Peak () is a mountain in the U.S. state of Arizona, and at is the highest point in the Quinlan Mountains. It is the location of the Kitt Peak National Observatory. The radio telescope at the observatory is one of ten dishes comprising the ...

in April 1993. This

was named after Nessus, a

from

Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and a genre of ancient Greek folklore, today absorbed alongside Roman mythology into the broader designation of classical mythology. These stories conc ...

, who poisoned and was killed by the divine hero

Heracles Heracles ( ; ), born Alcaeus (, ''Alkaios'') or Alcides (, ''Alkeidēs''), was a Divinity, divine hero in Greek mythology, the son of ZeusApollodorus1.9.16/ref> and Alcmene, and the foster son of Amphitryon.By his adoptive descent through ...

. The official was published by the

Minor Planet Center The Minor Planet Center (MPC) is the official body for observing and reporting on minor planets under the auspices of the International Astronomical Union (IAU). Founded in 1947, it operates at the Smithsonian Astrophysical Observatory. Funct ...

on 22 April 1997 (). A symbol derived from that for

, ( x14px), was devised in the late 1990s by German astrologer Robert von Heeren. It replaces Chiron's K with an N for Nessus.

Physical characteristics

Nessus has a very red color ( RR), with a B–R magnitude of 1.847 and 1.88, respectively.

Color indices In astronomy, the color index is a simple Numerical analysis, numerical Expression (mathematics), expression that determines the color of an object, which in the case of a star gives its temperature. The lower the color index, the more blue (or ...

were also determined by Bauer (2003) and Hainaut (2002, 2012).

Rotation period

As of 2018, no rotational

lightcurve In astronomy, a light curve is a graph (discrete mathematics), graph of the Radiance, light intensity of a celestial object or region as a function of time, typically with the magnitude (astronomy), magnitude of light received on the ''y''-axis ...

of Nessus has been obtained from photometric observations. However, a brightness variation of 0.5

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

was measured in the 1990s, indicating that the body has a non-spherical, elongated shape. The body's

rotation period In astronomy, the rotation period or spin period of a celestial object (e.g., star, planet, moon, asteroid) has two definitions. The first one corresponds to the '' sidereal rotation period'' (or ''sidereal day''), i.e., the time that the objec ...

and pole remain unknown.

Diameter and albedo

According to the

Herschel Space Observatory The Herschel Space Observatory was a space observatory built and operated by the European Space Agency (ESA). It was active from 2009 to 2013, and was the largest infrared telescope ever launched until the launch of the James Webb Space Telesco ...

with its PACS instrument, Nessus measures 57 kilometers in diameter and its surface has an

albedo Albedo ( ; ) is the fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...

of 0.086, while infrared observations with the

Spitzer Space Telescope The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), was an infrared space telescope launched in 2003, that was deactivated when operations ended on 30 January 2020. Spitzer was the third space telescope dedicate ...

gave a diameter of 60 kilometers with an albedo of 0.065. The ''Collaborative Asteroid Lightcurve Link'' assumes a

carbonaceous Carbonaceous refers to something relating to, containing, or composed of carbon. It is a descriptor used for the attribute of any substance rich in carbon. Particularly, ''carbonaceous hydrocarbons'' are very unsaturated, high- molecular-weight h ...

standard albedo of 0.057 and derives a diameter of 68.48 kilometers based on an absolute magnitude of 9.55.

In popular culture

Nessus is a playable destination in the 2017 video game ''

Destiny 2 ''Destiny 2'' is a free-to-play online first-person shooter video game developed by Bungie. It was originally released as a pay-to-play game in 2017 for PlayStation 4, Xbox One, and Windows. It became free-to-play, utilizing the games as a se ...

'', after previously being referenced in the series' 2014 debut entry ''

Destiny Destiny, sometimes also called fate (), is a predetermined course of events. It may be conceived as a predetermined future, whether in general or of an individual. Fate Although often used interchangeably, the words ''fate'' and ''destiny'' ...

''. Known simply as "Nessus," it is described as a planetoid that has been

terraformed Terraforming or terraformation ("Earth-shaping") is the hypothetical process of deliberately modifying the atmosphere, temperature, surface topography or ecology of a planet, moon, or other body to be similar to the environment of Earth to make ...

by a

cybernetic Cybernetics is the transdisciplinary study of circular causal processes such as feedback and recursion, where the effects of a system's actions (its outputs) return as inputs to that system, influencing subsequent action. It is concerned with ...

species known as the Vex into a "machine world".

References

External links

Selected Notable Spacewatch Discoveries
www.spacewatch.lpl.arizona.edu (archived)

Zane B. Stein
Dictionary of Minor Planet Names
Google books

– Minor Planet Center * * {{DEFAULTSORT:Nessus Centaurs (small Solar System bodies) 007066 Named minor planets 19930426