The term "Trojan asteroid" is normally understood to specifically mean the Jupiter trojans because the first Trojans were discovered near Jupiter's orbit and Jupiter currently has by far the most known Trojans. == Observational history == In 1772, Italian-born mathematician Joseph-Louis Lagrange, in studying the restricted three-body problem, predicted that a small body sharing an orbit with a planet but lying 60° ahead or behind it will be trapped near these points.
Barnard made the first recorded observation of a trojan, (identified as A904 RD at the time), in 1904, but neither he nor others appreciated its significance at the time.
Jupiter trojans are distributed in two elongated, curved regions around these Lagrangian points with an average semi-major axis of about 5.2 AU. The first Jupiter trojan discovered, 588 Achilles, was spotted in 1906 by German astronomer Max Wolf.
The object's identity was not understood until its orbit was calculated in 1999. The first accepted discovery of a trojan occurred in February 1906, when astronomer Max Wolf of Heidelberg-Königstuhl State Observatory discovered an asteroid at the Lagrangian point of the Sun–Jupiter system, later named 588 Achilles.
In 1906–1907 two more Jupiter trojans were found by fellow German astronomer August Kopff (624 Hektor and 617 Patroclus).
By 1938, 11 Jupiter trojans had been detected.
This number increased to 14 only in 1961.
The object's identity was not understood until its orbit was calculated in 1999. The first accepted discovery of a trojan occurred in February 1906, when astronomer Max Wolf of Heidelberg-Königstuhl State Observatory discovered an asteroid at the Lagrangian point of the Sun–Jupiter system, later named 588 Achilles.
As instruments improved, the rate of discovery grew rapidly: by January 2000, a total of 257 had been discovered; by May 2003, the number had grown to 1,600.
Jupiter-trojan families are much smaller in size than families in the asteroid belt; the largest identified family, the Menelaus group, consists of only eight members. In 2001, 617 Patroclus was the first Jupiter trojan to be identified as a binary asteroid.
As instruments improved, the rate of discovery grew rapidly: by January 2000, a total of 257 had been discovered; by May 2003, the number had grown to 1,600.
By 2003 roughly a dozen dynamical families were identified.
Like main-belt asteroids, Jupiter trojans form families. As of 2004, many Jupiter trojans showed to observational instruments as dark bodies with reddish, featureless spectra.
The Maxwellian distribution of the rotational periods of Jupiter trojans may indicate that they have undergone a stronger collisional evolution compared to the asteroid belt. In 2008 a team from Calvin College examined the light curves of a debiased sample of ten Jupiter trojans, and found a median spin period of 18.9 hours.
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