Trojan (astronomy)
Trojans are asteroids in the broader sense that precede or follow a planet in its orbit around the central star as a co-orbital objects. In a narrower sense, it is the two groups of asteroids that orbit the Sun on the same path as Jupiter, but precede it with an average distance of 60 ° and follow.
The Trojans found so far are named after the people of Homer's Iliad: the anticipatory asteroids according to the Greek (except for Hector ), the lagging after the Trojan hero.
Location
The Trojans orbit around the libration or Lagrange points L4 and L5. These are the equilibrium points and are a special case in the otherwise difficult detachable three-body problem Represents the system Sun - Jupiter - Trojan forms for each of these small bodies a stable three-body system. So far in 3035 L4 and L5 in 1734 Trojan known (as of 30 December 2010), the total number is estimated at several thousand. The first Trojan, ( 588 ) Achilles, was discovered in 1906 by Max Wolf. By far the greatest Trojans likely in 1907 discovered ( 624) Hektor be an irregularly shaped asteroid of 370 × 195 km extent ( see also List of asteroids ).
Dark body - from far out?
The planet Jupiter has by its huge mass enormous influence on the outer solar system and causes numerous instabilities of the asteroids and their orbits. Therefore, many astronomers believe that in the field of Trojan horse is a continual slow changes in progress.
Your unexpectedly large number (1960 were known only 20) is explained by mutual collisions. Because they are similar to dark or dark with albedos by 0.04 as the asteroids in the outer solar system, many are believed to date from there (Trans Neptune ). Chance, Trojans should again be solved by perturbations or shocks of the libration points and drift in the direction of Mars' orbit.
Trojans of other planets
The planets have so far been discovered only by Mercury and Saturn not Trojans.
Venus Trojans and companion
In July 2013 was found in the Venus for the first time a Trojan, which received the designation in 2013 ND15. Previously, since 2001, was found already the quasi-satellite ( 322756 ) CK32 2001, 2002 and 2012 VE68 XE133. The less than 100 meters wide in 2013 ND15 was identified as the first real Venus Trojans, however, the asteroid will leave within about 500 years, his Trojan train again and again to a quasi-satellite.
Earth Trojans and companion
From the Earth is so far only a Trojan known, in July 2011, the asteroid was identified in 2010 TK7 as Trojans. Furthermore, there is the asteroid 2002 AA29, the L4 and L5 shuttles back and forth between the Lagrangian points. After the collision theory, the formation of the Moon describing a planet ( Theia ) that caused by a subsequent collision with the Earth for the formation of the Moon developed in the L4 point of the Earth's orbit.
Mars Trojans
In 1990, a Mars Trojan was discovered in the libration point L5 of Mars, the Eureka was baptized. By now you have six more Mars Trojan discovered: (101429) 1998 VF31, ( 311999 ) 2007 NS2, 2001 DH47, 2011 SC191, 2011 UN63 and ( 121514 ) 1999 UJ7, of which the latter L4 point. From the Minor Planet Center, the four numbered so far are, however, not confirmed. An eighth object called 2011 SL25 is treated as a trojan candidate.
Uranus Trojans
Mid-year 2013, the date only Trojan has been discovered orbiting on the Uranus orbit around the sun. The asteroid 2011 QF99 runs his planet to libration point L4 ahead for at least 700,000 years and retains its position in about for the next one million years at. After that, he will be again for Centaur. The discovery of 60 km in diameter asteroid made of ice and rock in the art for a surprise, as was previously thought, it could be due to the gravitational influence of Jupiter and Neptune are no Uranus Trojans.
Neptune Trojans
End of 2001, they found a Trojan and 60 ° in front of Neptune. Taken with the 4 -m telescope at Cerro Tololo, the 230 - km - body received the asteroid number 2001 QR322, but was " saved " after a year. It orbits the sun - just like Neptune - in 166 Earth years. Meanwhile, 8 more Neptune Trojans known: 2004 UP10, 2005 TN53, 2005 TO74, 2006 RJ103, 2007 VL305 and 2004 KV18, 2008 and 2011 LC18 HM102. The six former are all on L4, the last three at L5.
Originally, the L4- position was also adopted in 2008 LC18. On 12 August 2010, the Department of Terrestrial Magnetism ( DTM ) of the Carnegie Institution of Washington in Washington, D.C. was known, however, that in 2008 LC18 moved on long -range position L5. It is the first recorded Neptune Trojans on this position.
On August 24, 2014, the spacecraft New Horizons is the Lagrangian point L5 cross the orbit of Neptune. There, it is hoped that the discovery of more Trojans.
Trojan moons of
Four Trojans are in the moon system of the planet Saturn. Thus the Saturn 's moon Tethys, the small moons Telesto in his L4- L5 and Calypso in his point. Saturn's moon Dione has the moon Helene L4 point and the moon Polydeuces in the L5- point of its path.
In the L4 and L5 points of the orbit of Earth's moon very faint dust clouds were found that Kordylewskischen clouds that are pronounced even weaker than the weak Gegenschein.
Moons of Trojans
On September 22, 2001, a moon of a Trojan was first discovered Menoetius, from ( 617) Patroclus, the moves on the L5 point. Since then, three other moons of Jupiter Trojans were detected. The moons of the asteroid (17365) 1978 VF11 and ( 29314 ) Eurydamas also move to L5, the moon of ( 624) Hektor so far only one on L4. From other Trojans except those of Jupiter 's moons are not yet known.