4489 Dracius

Orbit and classification

Dracius is a dark Jovian asteroid orbiting in the leading Greek camp at Jupiter's Lagrangian point, 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 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 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 (M.P.C. 16414). As of 2018, it had not been named. On 14 May 2021, the object was named by the Working Group for Small Bodies Nomenclature (WGSBN), after Dracius 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 asteroids). Since then, several have been named:

• 3708 Socus – named in May 2021
• 4035 Thestor – named in May 2021
• 4489 Dracius – named in May 2021
• 4715 Medesicaste – 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 (S3OS2), Dracius is a dark D-type asteroid. It has also been characterized as a D-type by Pan-STARRS' survey.

On 18 December 2012, Dracius has occulted 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, as well as Daniel Coley and Robert Stephens at the Center for Solar System Studies, California, in collaboration with Linda French and Brian Warner. Lightcurve analysis gave a well-defined rotation period 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

References

1. (April 2011). "Preliminary Results from a Study of Trojan Asteroids". Minor Planet Bulletin. link
2. (October 2016). "Lightcurves of Jovian Trojan Asteroids from the Center for Solar System Studies: L4 Greek Camp and Spies". Minor Planet Bulletin. link
3. (January 2016). "Large L5 Jovian Trojan Asteroid Lightcurves from the Center for Solar System Studies". Minor Planet Bulletin. link
4. [http://www.asteroidoccultation.com/2012_12/1218_4489_27150.htm Asteroid Occultation Updates] {{webarchive. link. (2012-07-11)