Astronomers establish high-inclination asteroids` strength

Washington: Astronomers used the Subaru Prime Focus Camera (Suprime-Cam) that is mounted on the Subaru Telescope to observe faint asteroids that have highly inclined orbits. The astronomers found that a smaller fraction of tiny bodies occur among high-inclination asteroids than those near the ecliptic plane. This means that large asteroids in high-velocity collisions between asteroids probably have a greater increase of strength in resisting disruption than those in the present mean-velocity collisions. Clarification of the relationship between collisional velocity and asteroids` disruptive strength is helpful in understanding the collisional evolution of asteroids in the early Solar System. A so-called "catastrophic collision", when objects suddenly hit each other with great force and incur significant damage, alters asteroids, the fragments of which become newly-born asteroids. Collisional evolution refers to changes in the size and number of asteroids as collisions repeat over time. Asteroids of a certain size decrease, because larger-bodied objects may fragment after catastrophic collisions. The primary factor controlling the balance between the increase and decrease in the size and number of asteroids through continuous collisions is the asteroid`s material strength against impacts. The strength of asteroids larger than about 100 meters in diameter increases with size, because gravity holds such larger objects together in a process called "gravitational binding." The population distribution of asteroids results from how much their strength against collisions increases in relation to their size. Therefore, measurements of their population distribution indicate properties of asteroids` strength and provide information necessary for investigating the collisional history of the asteroid belt.