How faraway asteroid with its moon may have formed
Researchers have said that exotic orbit for the largest Trojan asteroid, (624) Hektor -- the only one known to possess a moon, may be products of the collision of two icy asteroids.
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.
Trojan asteroids are those that are temporarily trapped in regions 60 degrees in front of or 60 degrees behind the planet Jupiter in its orbit around the Sun.
The research, conducted with expert assistance from colleagues at the Institut de Mecanique Celeste et de Calcul des Ephemerides (IMCCE) of the Observatoire de Paris, revealed that the 12 km moon orbits the large 250 km asteroid every 3 days at a distance of 600 km in an ellipse inclined almost 45 degrees with respect to the asteroid's equator.
Matija Cuk, coauthor and scientist at the Carl Sagan Center of the SETI Institute, said that the orbit of the moon is elliptical and tilted relative to the spin of Hektor, which is very different from other asteroids with satellites seen in the main-belt.
He said, however, they did computer simulations, which include Hektor being a spinning football shape asteroid and orbiting the Sun, and found that the moon's orbit is stable over billions of years.
Josef Durech, co-author and researcher at the Charles University in Prague, said that they built several models of equal quality from the photometric data, but they favored a model made of two lobes since some of the best adaptive optics observations suggest that the Trojan asteroid has a dual structure.
The team speculated that the moon could be ejecta produced by a slow encounter that formed the bi-lobed asteroid, but emphasized the need for robust and accurate simulations.
The results have been published in Astrophysical Journal Letters.
(Posted on 01-03-2014)