7066 Nessus is a very red

centaur A centaur ( ; grc, κένταυρος, kéntauros; ), or occasionally hippocentaur, is a creature from Greek mythology with the upper body of a human and the lower body and legs of a horse. Centaurs are thought of in many Greek myths as being ...

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 nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...

in the outer Solar System. It was discovered on 26 April 1993, by astronomers of the Spacewatch program at the Kitt Peak National Observatory in Tucson, Arizona. The dark and reddish minor planet 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 minor planets between the classical

asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

s and the trans-Neptunian objects. 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 long ...

of 24.64 AU). Its orbit has an eccentricity of 0.52 and an inclination of 16 ° with respect to the ecliptic. At its perihelion (11.9 AU), it moves much closer to the Sun than Uranus (19.2 AU) but not as close as Saturn (9.6 AU), while at its aphelion (37.4 AU), it moves out well beyond the orbit of

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

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

perturbations Perturbation or perturb may refer to: * Perturbation theory, mathematical methods that give approximate solutions to problems that cannot be solved exactly * Perturbation (geology), changes in the nature of alluvial deposits over time * Perturbatio ...

by the giant planets. ''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 (not officially credited), working with the Spacewatch program, at Kitt Peak National Observatory on 26 April 1993. The discovery was announced on 13 May 1993 in an '' IAU Circular'' (IAUC 5789) of the Central Bureau for Astronomical Telegrams. It was the third discovery of a centaur after

2060 Chiron 2060 Chiron is a 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—bodies orb ...

and

5145 Pholus 5145 Pholus is an eccentric 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 (uncredited) of UA's Space ...

, discovered by

Charles Kowal Charles Thomas Kowal (November 8, 1940 – November 28, 2011) was an American astronomer known for his observations and discoveries in the Solar System. As a staff astronomer at Caltech's Mount Wilson and Palomar Mountain observatories between ...

and David Rabinowitz in 1977 and 1992, respectively. The body's observation arc begins with its official discovery observation at Kitt Peak in April 1993. This minor planet was named after Nessus, a

from Greek mythology, who poisoned and was killed by the divine hero Heracles. 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. Function ...

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 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 hotter) the object is. Conversely, the large ...

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

Rotation period

As of 2018, no rotational lightcurve of ''Nessus'' has been obtained from photometric observations. However, a brightness variation of 0.5 magnitude was measured in the 1990s, indicating that the body has a non-spherical, elongated shape. The body's

rotation period The rotation period of a celestial object (e.g., star, gas giant, planet, moon, asteroid) may refer to its sidereal rotation period, i.e. the time that the object takes to complete a single revolution around its axis of rotation relative to the ...

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 Telesc ...

with its PACS instrument, ''Nessus'' measures 57 kilometers in diameter and its surface has an albedo 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. Operations ended on 30 January 2020. Spitzer was the third space telescope dedicated to infrared astronomy, f ...

gave a diameter of 60 kilometers with an albedo of 0.065. The ''Collaborative Asteroid Lightcurve Link'' assumes a carbonaceous 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 present in the online video game Destiny 2, and is referenced in its predecessor Destiny 1. Nessus can be visited by players. In the game, Nessus has been terraformed by a cybernetic 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