Contents

4489 Dracius

4489 Dracius

Shape model of Dracius from its lightcurve
Discovery [1]
Discovered by	E. Bowell
Discovery site	Lowell Obs.
Discovery date	15 January 1988
Designations
MPC designation	(4489) Dracius
Named after	Dracius (Greek mythology)[2]
Alternative designations	1988 AK · 1980 KA1 1989 AQ1
Minor planet category	Jupiter trojan [1][3][4] Greek [5][6] · background [6]
Adjectives	Dracian
Orbital characteristics [3]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc	37.94 yr (13,857 d)
Aphelion	5.5196 AU
Perihelion	4.9173 AU
Semi-major axis	5.2184 AU
Eccentricity	0.0577
Orbital period (sidereal)	11.92 yr (4,354 d)
Mean anomaly	174.79°
Mean motion	0° 4m 57.72s / day
Inclination	22.224°
Longitude of ascending node	86.540°
Argument of perihelion	6.5830°
Jupiter MOID	0.1975 AU
TJupiter	2.8480
Physical characteristics
Mean diameter	76.60±0.41 km[7] 92.93±7.4 km[8] 95.02±2.47 km[9]
Synodic rotation period	12.580±0.001 h[10][a] 12.58±0.1 h[11] 12.582±0.001 h[12][a] 12.582±0.004 h[13]
Geometric albedo	0.050±0.003[9] 0.0514±0.009[8] 0.069±0.005[7]
Spectral type	D (SDSS-MOC)[14] D (S3OS2)[15] D (Pan-STARRS)[4][16] V–I = 0.950±0.037[4]
Absolute magnitude (H)	9.00[1][3][4][9] 9.1[7] 9.12±0.22[16]

4489 Dracius, (prov. designation: 1988 AK), is a large Jupiter trojan from the Greek camp, approximately 90 kilometers (56 miles) in diameter. It was discovered on 15 January 1988, by American astronomer Edward Bowell at the Anderson Mesa Station of the Lowell Observatory near Flagstaff, Arizona, in the United States.^[1] The dark D-type asteroid belongs to the 50 largest Jupiter trojans and has a rotation period of 12.58 hours.^[4] It was named after Dracius from Greek mythology, who was a commander of the Epeans who fought against Hector.^[2]

Orbit and classification[edit]

Dracius is a dark Jovian asteroid orbiting in the leading Greek camp at Jupiter's L₄ 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.^[6][17] 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.^[3]

The body's observation arc begins with its first observation as 1980 KA₁atCrimea–Nauchnij in May 1980, almost 8 years prior to its official discovery observation at Anderson Mesa.^[1]

Numbering and naming[edit]

This minor planet was numbered on 8 June 1990 (M.P.C. 16414).^[18] As of 2018, it had not been named.^[1] 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.^[2]

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 :

Physical characteristics[edit]

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.^[14][17][15] It has also been characterized as a D-type by Pan-STARRS' survey.^[4][16]

On 18 December 2012, 1988 AK 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.^[19]

Rotation period[edit]

Since 1992, several rotational lightcurvesofDracius 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 (U=3/3).^{[4][10][11][12][13][a]}

Diameter and albedo[edit]

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.^[7][8][9]

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.^[4]

Notes[edit]

References[edit]

External links[edit]

• Lightcurve Database Query (LCDB), at www.minorplanet.info
• Discovery Circumstances: Numbered Minor Planets (1)–(5000) – Minor Planet Center
• 4489 DraciusatAstDyS-2, Asteroids—Dynamic Site
  • Ephemeris · Observation prediction · Orbital info · Proper elements · Observational info
• 4489 Dracius at the JPL Small-Body Database
  • Close approach · Discovery · Ephemeris · Orbit diagram · Orbital elements · Physical parameters