Troy Groupasteroid(Trojan astroids)JupiterShare the track, circle togethersunlightA large group of asteroids in motion.Judging from the coordinate system fixed on Jupiter, they areLagrange pointThe two stable points are located at 60 degrees in front (L4) and behind (L5) of Jupiter's orbit.
In 2006,HawaiiKeck Observatory A team of, announced that they had measured an asteroid (617), Patroclus, whose density was lower than ice, so they suggested that it was a pair of asteroids, and many trojan asteroids might be binary stars.
Barnard is believed to be the first person to observe an asteroid in Troy.In 1904, no one noticed his observation, but thought that what he observed wasSaturn's satelliteIapetus(Phoebe), because at that time, the distance between the two in the sky was only two minutes of arc, or just onefixed star。Barnard's observation was not taken seriously until the Trojanian asteroid (12126) 1999 RM11 was discovered and its orbit was confirmed again in 1999.But it is probably only historians who are interested in confirming which celestial body Barnard saw.
In February 1906, German astronomersMax Wolf Max Wolf discovered a solar JupiterLagrange pointLfourAsteroids onHomerThe hero of Iliad in the fairy taleAchillesNamed (588) Achilles, it showed abnormal orbital motion within a few months, and many other asteroids were also found near this point soon (including another Lagrangian point L of the sun Jupiter systemfive）。
As of September 2007, 2239 Trojanian asteroids have been confirmed, of which 1192 are located in LfourPoint, 1047 at LfiveIn October 1999, there were only 177 numbers, 877 in July 2004, 1826 in August 2005, and 2049 in June 2006.In addition, there are 6 in the orbit of Neptune and 4 in the orbit of Mars.The largest trojan asteroid is (624) Hektor, measured 370 kilometers long and 195 kilometers wide.There is no doubt that there are many smaller celestial bodies that cannot be seen by instruments.
Causes
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According to the original specification, the major half axis of the trojan asteroid's orbit is between 5.05 and 5.40 AU, and it is in twoLagrange pointWithin an arc area of.This rule also applies to similar cases of other celestial bodies, in which major celestial bodies will be marked, such as:NeptuneTrojanian asteroid 2001 QR322.
In 2006, HawaiiKeck Observatory A team of, announced that they observed that the density of the asteroid Patroclus was lower than that of frozen water, so they speculated that it might be a pair of asteroids, and many trojan asteroids might be binary stars.
According to traditional theory, Troy asteroid was formed by stars near Jupiter, and was captured by its gravity with the growth of Jupiter.But this theory cannot explain TroyAsteroid beltOfTrack planedip angle.Others believe that the Troy asteroid belt was formed in a relatively far place, but because Jupiter has disturbed the original motion of these asteroids, they were brought to roughly the same orbit.
Naming rules
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Troy asteroids are located 60 degrees ahead or behind Jupiter.
In 1906, after Max Wolf named asteroid 588 after Achilles, the Greek hero in the Trojan War, other Trojan asteroids were named after the Greek heroes in the Iliad dramas. In fact, they are only limited to L4 points, so they are also called the Greek group or the Achilles group represented by Achilles;At L5, it is named after the hero of Troy, whose representative is Patroclus, so it is also called Troy Group or Patroclus Group.Since there was no separate naming rule for Greece and Troy at that timeGreek groupThere is also the hero of Troy (624) Hector.
Because the characters of Iliad's Trojan War were usedTroy group asteroidTroy was originally only used to call asteroids in the same orbit as Jupiter, so when Mars andNeptuneAfter the discovery of asteroids at the Lagrange point of Mars, these Trojans must be called Trojans of Mars or Neptune.
Widely distributedTrojan asteroids , may also play an important role in satellite formation.In the leading positionLarge collision theoryIn the very early solar system, a planet the size of Mars collided with the Earth.Because the impact must not only hit the side of the earth, but also not be too violent (otherwise the two celestial bodies will be completely destroyed).So this hypothetical planetTheia (Theia) must be stable in the Earth solar system before hitting the EarthLagrange pointThen some factors slowly changed his orbit, and finally entered the orbit of collision with the young earth.
observation data
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In the circle is 2010TK7[1]
In July 2011, astronomers discovered the Earth's first trojan asteroid through the Wide Area Infrared Survey (WISE).The asteroid is located at the Sun Earth 4 Lagrange Point.This asteroid is called 2010 TK7, with a diameter of nearly 300 meters and a current distance of 80 million kilometers from Earth.The 2010 TK7 asteroid has a strange and disordered orbit. Normally, the Troy asteroid will not orbit on the right side of the Lagrange point, but will orbit the planet in a tadpole shaped orbit, which is caused by the gravitational effect of other stars in the solar system.The tadpole orbit of the 2010 TK7 asteroid is very large, close to the farthest end of the Earth's orbit to the sun.
[2]
In July 2023, according to a new research published in the journal Astronomy and Astrophysics, astronomers found the evidence that two planets outside the solar system may share the same orbit for the first time.The international research team observed the PDS70 system of Centaurus 370 light-years away.Two Jupiter like planets, PDS70b and PDS70c, are known to orbit this star.But the research team found a debris cloud in the orbit of PDS70b, which may be part of a new planet that is forming or has formed.If confirmed, this discovery will become the strongest evidence so far that two exoplanets can share the same orbit.[3]
