research project, performed at
The study of
asteroids was part of the PhD thesis research of
discovery, obtained by the participation of the Wise Observatory in an
international network of 15 institutions around the world, led by Petr Pravec from the Astronomical Institute of the
brightness changes of these asteroids allows us to derive their rotation
rates," said Polishook, "this is an essential property when studying
the origin and formation mechanism of these interesting objects”.
The pair asteroid 10484 Hecht moving in front of the background stars." Copy rights: David Polishook.
The research team
showed that all the asteroid pairs in the study had a specific relationship
between the larger and smaller members, with the smaller one always less than
60 percent of the size of its companion asteroid. The measurement fits
precisely the prediction of a theory developed in 2007 by a Colorado
University-Boulder aerospace engineering sciences Professor and Nature paper
co-author, Daniel Scheeres.
predicts that if a binary asteroid forms by rotational fission, the two can
only escape from each other if the smaller one is less than 60 percent the size
of the larger asteroid. During rotational fission the asteroids separate gently
from each other at relatively low velocities. “The smaller guy steals
rotational energy from the bigger guy, causing the bigger guy to rotate more
slowly and the size of the orbit of the two bodies to expand." Scheeres
said. "If the second asteroid is small enough, there is enough excess
energy for the pair to escape from each other and go into their own orbits
around the sun.”
An artist impression of a binary asteroid." Copy rights: W. M. Keck Observatory/Lynette Cook.
pairs were first discovered in 2008 by Nature paper co-author David Vokrouhlicky of
around the world were used for the study, with the most thorough observations,
of more than 320 hours, being made with the 0.46-meter and 1-meter telescopes
Observatory in the
The 1-meter telescope of the Wise Observatory,
"By now it
seems that most of the jigsaw puzzle is solved," Polishook said. "The
sunlight is responsible for the spinning-up of the asteroids, as if they were
windmills reacting to the wind; the fragile nature of asteroids, the rubble
pile structure, allows the centrifugal force to disrupt them; and there is
sufficient time for this process to recur again and again making asteroids
smaller and rounder."
An illustration of the 'separated pairs of asteroids' formation mechanism." Copy rights: David Polishook.
important for the understanding of life on Earth,” said Scheeres. He pointed to the Chicxulub
asteroid, believed to have impacted the Earth near the
An artist impression of a binary asteroid." Copy rights: ESO.
Other co-authors of
the Nature paper are from institutions in the