3548 Eurybates (/jʊˈrɪbətiːz/ yə-RIB-ə-teez) is a carbonaceous Jupiter trojan from the Greek camp and the parent body of the Eurybates family, approximately 68 kilometers (42 miles) in diameter. It is a target to be visited by the Lucy mission in August 2027. Discovered during the second Palomar–Leiden Trojan survey in 1973, it was later named after Eurybates from Greek mythology. This C-type asteroid is among the 60 largest known Jupiter trojans and has a rotation period of 8.7 hours. Eurybates has one kilometer-sized satellite, named Queta, that was discovered in images taken by the Hubble Space Telescope in September 2018.

Eurybates was discovered on 19 September 1973, by Dutch astronomers Ingrid and Cornelis van Houten at Leiden, on photographic plates taken by Tom Gehrels at the Palomar Observatory in California, United States. In 1951, it was first observed as 1954 CB at the Goethe Link Observatory, extending the asteroid's observation arc by 22 years prior to its official discovery observation at Palomar.^[1] Since the discovery of 588 Achilles by Max Wolf in 1906, more than 7,000 Jupiter trojans, with nearly 4,600 bodies in the Greek camp, have already been discovered.^[6]

Eurybates is a dark Jupiter trojan asteroid orbiting in the leading Greek camp at Jupiter's L₄ Lagrangian point, 60° ahead of Jupiter's orbit in a 1:1 resonance (see Trojans in astronomy).^[6][7] It orbits the Sun at a distance of 4.7–5.7 AU once every 11 years and 10 months (4,321 days; semi-major axis of 5.19 AU). Its orbit has an eccentricity of 0.09 and an inclination of 8° with respect to the ecliptic.^[4]

Eurybates has been characterized as a carbonaceous C-type asteroid by both the Lucy mission team and Brian Warner's Lightcurve Data Base.^[5][11] The overall spectral type for members of the Eurybates family is that of a C- and P-type.^[13]: 23

This minor planet was named after Eurybates, the Ancient hero from Greek mythology, who was a herald for the Greek armies during the Trojan War.^[3] The official naming citation was published by the Minor Planet Center on 28 April 1991 (M.P.C. 18138).^[21]

Eurybates has one known satellite, named Queta after Mexican Olympic athlete Enriqueta Basilio.^[26] Provisionally designated S/2018 (3548) 1, the satellite was discovered by Keith S. Noll and colleagues in images taken with the Hubble Space Telescope in September 2018.^[25][27] Subsequent follow-up observations later confirmed the satellite's existence, and the discovery was announced on 9 January 2020. The satellite was given the name Queta on 15 October 2020, in accordance with the International Astronomical Union's Olympic athlete naming convention for small Jupiter trojans (H > 12). In the naming citation, Enriqueta Basilio was recognized as the first woman torchbearer at the 1968 Summer Olympics, analogous to the role of heralds like Eurybates.^[26]

Queta is extremely faint, with an apparent magnitude of ~26.77.^[25] It is at least 6,000 times fainter than Eurybates, suggesting that Queta is likely very small, about 1.2 ± 0.4 km (0.75 ± 0.25 mi) in diameter if it has the same albedo as Eurybates.^[24] The satellite has an orbital period of 82.46±0.06 days, with a semi-major axis of 2,350 ± 11 km (1,460.2 ± 6.8 mi) and low eccentricity of 0.125±009.^[10] It is probably a fragment of Eurybates since it is part of a known collisional family.^[28][10] The presence of the satellite does not pose any adverse effects on the Lucy mission, though it provides an additional object for the spacecraft to study during its flyby in 2027.^[29][28]