[1][2] The dark D-type asteroid measures approximately 133 kilometers (83 miles) in diameter which makes it one of the 10 largest Jupiter trojans.

[3] Achilles is the first known example of the stable solution of the three-body problem worked out by French mathematician Joseph Lagrange in 1772, after whom the minor planet 1006 Lagrangea is named.

Achilles's rotation period of 7.3 hours is somewhat shorter than that of most other large Jupiter trojans but close to that of 911 Agamemnon, 3451 Mentor and 3317 Paris, which are similar in size (see table below).

[12] From July 2007 until September 2008, coordinated photometric observations were carried out by astronomers at Simeiz (Crimea), Rozhen (Bulgaria), Maidanak (Uzbekistan) and Kharkiv (Ukraine) observatories.

[12] Alternative period determinations by Cláudia Angeli (7.0 h), Robert Stephens (7.312 h), Stefano Mottola (7.32 h) and Vincenzo Zappalà (12 h) are mostly in good agreement (U=1/3-/3/1).

It was named after Achilles, the legendary hero from Greek mythology and central figure in Homer's Iliad which tells the accounts of the Trojan War (also see 5700 Homerus and 6604 Ilias).