# Trojan Asteroid

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## Trojan asteroid

[‚trō·jən ′as·tə‚rȯid]
(astronomy)
One of a group of asteroids orbiting near the equilateral Lagranginan stability points of the sun-Jupiter system, which are located on Jupiter's orbit, 60° ahead of or 60° behind Jupiter. Also known as Jupiter Trojan.
More generally, an object that is orbiting near one of the equilateral Lagrangian stability points of any pair of bodies.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

## Trojan Asteroid

(also Trojan planet, Trojan), in astronomy, one of a group of asteroids that revolve around the sun in such a way that their mean celestial longitudes are always approximately 60° more or 60° less than the celestial longitude of Jupiter. The sun, Jupiter, and each of the Trojan asteroids form an approximate equilateral triangle in space.

The periods of revolution of the Trojans around the sun and, consequently, the Trojans’ mean distances from the sun are almost exactly equal to the period of revolution and the mean distance, respectively, of Jupiter. Asteroids with these characteristics of motion are named for heroes of the Trojan War; hence the term “Trojans.” The study of the Trojans is of great interest since the motion of each such asteroid corresponds approximately to the motion in the Lagrange problem, a special case of the three-body problem that has been completely solved (seeCELESTIAL MECHANICS).

In all, 15 Trojan asteroids are known; they were discovered between 1906 and 1950. Their mean eccentricity is 0.096, and their mean inclination to the plane of the ecliptic is 16.4°. The Trojans are faint objects, having stellar magnitudes of 12.6 to 15.0. The photometric mean diameter of the Trojans is 140 km, which has been determined on the assumption that their albedo equals the arithmetic mean of the albedos of Mars and Mercury.

References in periodicals archive ?
In 2006, a small team of astronomers led by Franck Marchis, astronomer at the Carl Sagan center of the SETI Institute, detected the presence of a small 12 km diameter moon around the large Trojan asteroid (624) Hektor.
A spectrum of this object was typical of that of a D type asteroid -70% of Trojan asteroids have this type of spectrum.
Thousands of Trojan asteroids circle the Sun in Jupiter's orbit, in the stable points roughly 60[degrees] ahead of and behind the giant planet itself.
We found evidence of the migration in the Trojan asteroids orbiting close to Jupiter," explains Simona Pirani, doctoral student in astronomy at Lund University, and the lead author of the study.
The NASA contract for launching the Lucy mission seeks to study Trojan asteroids of Jupiter.
NASA has announced it has selected Colorado-based United Launch Services LLC (ULS) to provide launch services for Lucy Mission, the the agency's first mission to explore Trojan asteroids, the company said.
The Lucy mission will explore the trojan asteroids of Jupiter, a group of objects captured from the asteroid belt.
TROJAN ASTEROIDS orbit ahead of and behind Mars in the stable regions where the gravitational pull of the Red Planet balances that of the Sun.
The objects of their research include comets, asteroids, planetary rings, and Trojan asteroids. Among their methods are the nonlinear dynamical method, the mapping method, the symplectic integrator, and spectral analysis.
Others, called "Trojan asteroids," cloud beside Jupiter, held captive by the planet's and the sun's gravity (attracting force).
This is a comparatively stable gravitational position, called a Trojan situation because it is also the position of the Sun, Jupiter, and the Trojan asteroids (see 1906).

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