Astronomers
have detected three new rocky bodies which share the same orbit as Neptune as
it travels around the Sun.
The
finding, detailed in the June 16 issue of the journal Science, brings the
total number of the gas giant's asteroid companions, or "Trojans," up to four.
The highly
inclined orbit of one of them supports the hypothesis that the Neptune Trojans
were captured from a much larger asteroid "cloud" that surrounds the
planet, and that they are not the broken remains of some larger object as some
scientists have speculated.
The
Trojans gather around one of Neptune's two so-called "Lagrangian"
points. In these regions--located 60 degrees in front of and behind the planet
in its orbit--the Sun and Neptune's gravity combine to ensnare passing objects.
The orbit
of one of the new Trojans is tilted about 25 degrees relative to the plane that
Neptune orbits the Sun, compared to only about 5 degrees for the other three
Trojans.
The way the
survey was set up, it was very unlikely that such a highly inclined object
would be detected. The fact that it was indicates that there are at least as
many--and possibly more--highly inclined Trojans existing far from the solar
system plane compared to low inclination ones, said study team member Chadwick
Trujillo of the Gemini Observatory Hawaii.
"The
Neptune Trojans are a thick 'swarm,' not a thin population confined to the
plane," Trujillo told SPACE.com.
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