Professor's research on asteroids published in Nature magazine

ASU News ^ | August 25, 2010 | Appalachian State University

[SunkenCiv]

"It turns out that there are a significant number of asteroids that aren't just a single object, but two and even on occasion three in orbit around one another," Pollock said. He and his colleagues record information related to changes in amount of light reflected from asteroids. Sometimes this indicates the existence of a pair of asteroids that are revolving around each other...

"When a single, irregularly shaped asteroid spins, the amount of reflective area changes and it appears to change brightness," Pollock said. "When you have two rotating asteroids revolving around one another, the brightness changes are much more complicated but analysis of those fluctuations in light provides important information about the size, mass and density for them. The only other way to get such information is to send a spacecraft to the asteroid."

...Asteroid pairs or binary asteroids are often formed when a single asteroid splits or a conglomeration of pieces held together by gravity breaks apart as the asteroid spins. An increase in the spin speed is caused by the heating and cooling of the asteroid's surface as it passes in and out of sunlight.

"As the asteroid spins faster and faster, eventually it gets to the point that it is spinning so fast a chunk of it breaks off like mud flying off of a tire. That process is referred to as rotational fission," Pollock said.

[SunkenCiv]

• Formation of asteroid pairs by rotational fission [Nature 466, 1085-1088] -- Abstract: Pairs of asteroids sharing similar heliocentric orbits, but not bound together, were found recently1, 2, 3. Backward integrations of their orbits indicated that they separated gently with low relative velocities, but did not provide additional insight into their formation mechanism. A previously hypothesized rotational fission process4 may explain their formation—critical predictions are that the mass ratios are less than about 0.2 and, as the mass ratio approaches this upper limit, the spin period of the larger body becomes long. Here we report photometric observations of a sample of asteroid pairs, revealing that the primaries of pairs with mass ratios much less than 0.2 rotate rapidly, near their critical fission frequency. As the mass ratio approaches 0.2, the primary period grows long. This occurs as the total energy of the system approaches zero, requiring the asteroid pair to extract an increasing fraction of energy from the primary's spin in order to escape. We do not find asteroid pairs with mass ratios larger than 0.2. Rotationally fissioned systems beyond this limit have insufficient energy to disrupt. We conclude that asteroid pairs are formed by the rotational fission of a parent asteroid into a proto-binary system, which subsequently disrupts under its own internal system dynamics soon after formation.

[SunkenCiv]

· join · view topics · view or post blog · bookmark · post new topic · subscribe ·

[Jack Hydrazine]

You bet your asteroids!

[SunkenCiv]

You bet your sweet asteroids I am.

[SunkenCiv]

• Asteroid discovered in Neptunian dead zone [L5 Neptune Trojan asteroid]