4489 Dracius, ( ''prov. designation'': ), is a large

Jupiter trojan The Jupiter trojans, commonly called trojan asteroids or simply trojans, are a large group of asteroids that share the planet Jupiter's orbit around the Sun. Relative to Jupiter, each trojan librates around one of Jupiter's stable Lagrange poin ...

from the

Greek camp This is a list of Jupiter trojans that lie in the Greek camp, an elongated curved region around the leading Lagrangian point (), 60 ° ahead of Jupiter in its orbit. All the asteroids at Jupiter's point have names corresponding to participants ...

, approximately in diameter. It was discovered on 15 January 1988, by American astronomer Edward Bowell at the Anderson Mesa Station of the

Lowell Observatory Lowell Observatory is an astronomical observatory in Flagstaff, Arizona, United States. Lowell Observatory was established in 1894, placing it among the oldest observatories in the United States, and was designated a National Historic Landmark ...

near Flagstaff, Arizona, in the United States. The dark

D-type asteroid D-type asteroids have a very low albedo and a featureless reddish Asteroid spectral types, spectrum. It has been suggested that they have a composition of organic-rich silicates, carbon and anhydrous silicates, possibly with water ice in their inte ...

belongs to the 50 largest Jupiter trojans and has a

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 ...

of 12.58 hours. It was named after

Dracius In Greek mythology, Dracius (Ancient Greek: Δρακίος) was a commander of the Epeans of Elis, together with Meges and Amphion, during the Trojan War. See also * for Jovian asteroid 4489 Dracius Notes References * Homer Home ...

from Greek mythology, who was a commander of the Epeans who fought against Hector.

Orbit and classification

''Dracius'' is a dark Jovian

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. ...

orbiting in the leading Greek camp at Jupiter's

Lagrangian point In celestial mechanics, the Lagrange points (; also Lagrangian points or libration points) are points of equilibrium for small-mass objects under the influence of two massive orbiting bodies. Mathematically, this involves the solution of th ...

, 60 ° ahead of its orbit in a 1:1 resonance ''(see Trojans in astronomy)''. It is a non- family asteroid in the Jovian background population. It orbits the Sun at a distance of 4.9–5.5 AU once every 11 years and 11 months (4,354 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 5.22 AU). Its orbit has an eccentricity of 0.06 and an inclination of 22 ° with respect to the ecliptic. The body's observation arc begins with its first observation as ' at

Crimea–Nauchnij The Crimean Astrophysical Observatory (CrAO, obs. code: 095) is located at Nauchnij research campus, near the Central Crimean city of Bakhchysarai, on the Crimean peninsula. CrAO is often called simply by its location and campus name, ...

in May 1980, almost 8 years prior to its official discovery observation at Anderson Mesa.

Numbering and naming

This minor planet was numbered on 8 June 1990 (). As of 2018, it had not been named. On 14 May 2021, the object was named by the Working Group Small Body Nomenclature (WGSBN), after

from Greek mythology, who was a commander of the Epeans of Elis, who defended the Argive ships from Hector's attack during the Trojan War. Before ''Dracius'' was named, it belonged to a small group of only 8 unnamed minor planets with a designated number smaller than 5000. (All of them are Jupiter trojans or

near-Earth asteroid A near-Earth object (NEO) is any small Solar System body whose orbit brings it into proximity with Earth. By convention, a Solar System body is a NEO if its closest approach to the Sun (perihelion) is less than 1.3 astronomical units (AU). ...

s). Since then, several have been named : *

3708 Socus 3708 Socus ( ''provisional designation'': ) is a large Jupiter trojan from the Trojan camp, approximately in diameter. It was discovered on 21 March 1974, by staff members of the Cerro El Roble Observatory owned and operated by the Department of ...

– named in May 2021 *

4035 Thestor 4035 Thestor, ''provisional designation:'' 1986 WD, is a large Jupiter trojan from the Greek camp, approximately in diameter. It was discovered on 22 November 1986, by Japanese astronomers Kenzo Suzuki and Takeshi Urata at the Toyota Observato ...

– named in May 2021 * 4489 Dracius – named in May 2021 * * *

4715 Medesicaste 4715 Medesicaste ( ''prov. designation'': ) is a dark Jupiter trojan from the Trojan camp, approximately in diameter. It was discovered on 9 October 1989, by Japanese astronomer Yoshiaki Oshima at the Gekko Observatory east of Shizuoka, Japan. ...

– named in May 2021 * 4835 Asaeus *

Physical characteristics

In the SDSS-based taxonomy, as well as in both the Tholen- and SMASS-like taxonomy of the

Small Solar System Objects Spectroscopic Survey An asteroid spectral type is assigned to asteroids based on their emission spectrum, color, and sometimes albedo. These types are thought to correspond to an asteroid's surface composition. For small bodies that are not internally differentiated ...

(S3OS2), ''Dracius'' is a dark

. It has also been characterized as a D-type by Pan-STARRS' survey. On 18 December 2012, ' has

occulted An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks ...

the star TYC 2467-00054-1 over parts of the United States. The asteroid's brightness was measured at 16.1 and that of the star at 11.1 magnitude.

Rotation period

Since 1992, several rotational lightcurves of ''Dracius'' have been obtained from photometric observations by

Stefano Mottola This is a list of minor-planet discoverers credited by the Minor Planet Center with the discovery of one or several minor planets (such as near-Earth and main-belt asteroids, Jupiter trojans and distant objects). , the discovery of 612,011 numb ...

, as well as Daniel Coley and

Robert Stephens Sir Robert Graham Stephens (14 July 193112 November 1995) was a leading English actor in the early years of Britain's Royal National Theatre. He was one of the most respected actors of his generation and was at one time regarded as the natur ...

at the

Center for Solar System Studies This is a list of observatory codes (IAU codes or MPC codes) published by the Minor Planet Center. For a detailed description, ''see observations of small Solar System bodies''. List References * {{DEFAULTSORT:Observat ...

, California, in collaboration with Linda French and Brian Warner. Lightcurve analysis gave a well-defined

of 12.582 hours with a consolidated brightness amplitude between 0.20 and 0.26 magnitude ().

Diameter and albedo

According to the surveys carried out by the Japanese Akari satellite, the Infrared Astronomical Satellite IRAS, and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, ''Dracius'' measures between 76.60 and 95.02 kilometers in diameter and its surface has an albedo between 0.050 and 0.069. The ''Collaborative Asteroid Lightcurve Link'' adopts the results obtained by IRAS, that is, an albedo of 0.0514 and a diameter of 92.93 kilometers based on an absolute magnitude of 9.0.

Notes

References

External links

Lightcurve Database Query
(LCDB), at ''www.minorplanet.info''

– Minor Planet Center * * {{DEFAULTSORT:Dracius 004489 Discoveries by Edward L. G. Bowell 004489 Named minor planets 19880115