A UCLA researcher working with a team of astronomers has
determined that the asteroid Hermes, recently spotted for the first
time since 1937, is in fact two separate rocks travelling on an
orbit around the sun.
Jean-Luc Margot, a researcher for the department of earth and
space sciences, used radar equipment rather than optical
observations to come to the conclusion that Hermes is a binary
Hermes has been flying near the Earth undetected for the past 66
years until recently, when Brian Skiff caught a glimpse of it from
Arizona’s Lowell Observatory.
Through collaboration with other researchers at the Arecibo
Observatory in Puerto Rico, Margot estimated that each rock is
about 300 to 500 meters in diameter, roughly the size of a large
“The radar data allows us to predict, over a much longer
time span, what the actual trajectory of the object is,” said
Although Hermes is a near-Earth asteroid, meaning it was
originally ejected from the main belt of asteroids between the
orbit of Mars and Jupiter, Margot assured us that there is no
possibility of the asteroid impacting the earth ““ at least
not in our lifetime.
“It comes close enough to the earth that over thousands of
years, the orbits got nudged together,” said Mike Nolan, a
radar-imaging scientist at the Arecibo Observatory.
This explains why the asteroid was about 13 million kilometers
from the earth when it was observed on October 15, coming closer to
the Earth than Mars.
“Asteroids in the main belt of asteroids “¦
occasionally experience gravitational perturbations that eject them
into trajectories that cross the orbit of the Earth,” Margot
Currently, Margot and his team of astronomers are using the
radar system to determine physical properties of the asteroid, such
as its velocity, density and most importantly, trajectory.
“We’re trying to characterize the object as best as
we can,” Margot said.
The radar equipment they are using sends radio waves to Hermes,
which then sends echoes back to Earth. These echoes produce the
image of the two objects, help determine their sizes, show how they
spin in space, and help establish other aspects of the rocks.
After this information is collected, the researchers can
determine the orbital history of the asteroid.
There are several theories as to how the objects were
“(Hermes) is a banged up pile of rocks that came so close
to the earth that tidal forces pulled it to pieces and it never
came back together, although it can come back together in the
future,” Nolan speculated, referring to one theory of how the
Hermes came about.
Another theory was suggested by Brian Marsden, director of the
Minor Planet Center in Cambridge, MA.
“There have been interactions among the asteroids,
including those that have come near the Earth,” he said.
“If you have potential for collision among asteroids, and
there is a fair bit of evidence that we do, then the by-product of
collisions are companions.”
The data the team has amassed so far indicate that the two
elements of the asteroid are relatively equal, both in size and in
“They may be made of the same material. This is what one
would expect if the binary formed by tidal disruption during a
close encounter with a planet,” Margot said.
Margot and his team of researchers will continue observing the
asteroid at the Goldenstone Solar System Radar, located in
California, in order to determine what constitutes the two