Critically, the Baptistina family of asteroids - those that were formed when the larger asteroid destructively entered the main belt - were only formed around 80 million years ago.
It was once thought that asteroids in the main belt occasionally collided with one another, sending fragments into orbital resonance bands where they could be affected by the gravity of Jupiter or Saturn.
ECONOMIST: Celestial mechanics: A rock in a hard place | The
Scientists believe it would take an asteroid around 10 million years to travel from the main belt to Earth, so "this doesn't give a Baptistina fragment much time to get into a suitable position", said Dr Mainzer.
This gives the dinosaur-killing rock only 15 million years to move into a suitable place to be flung out of the main belt and to travel to Earth in time for the impact 65 million years ago.
Vesta and Ceres are the two most massive objects in the main asteroid belt.
The inner main-belt asteroid 5806 Archieroy was named after Professor Roy shortly after its discovery in 1986.
Although downward-looking diagrams of the Main Asteroid Belt make it look incredibly dense, the region has significant gaps, clumps and clusters.
They are believed to have broken away from the main asteroid belt between Mars and Jupiter and are our nearest neighbours in space after the Moon.
Abell says the best estimates now are that the Russian object was initially a rocky silicate asteroid that almost certainly originated from the main asteroid belt.
But astronomers have been unable to figure out how they get from the main asteroid belt between Mars and Jupiter to the vicinity of the Earth.
T. and an expert on the Main Asteroid Belt, points out, the belt could have never hosted a planet large enough to claim Mars as a satellite.
Right now, our economy is trapped in a vicious cycle: The turmoil on Wall Street means a new round of belt-tightening for families and businesses on Main Street--and as folks produce less and consume less, that just deepens the problems in our financial markets.
The government's main hope of boosting output lies in the Orinoco heavy-oil belt.
The main source of meteorites, Chinese folklore notwithstanding, is the asteroid belt between Mars and Jupiter, a rough-and-tumble region of our solar system in which would-be planets are upset by Jovian gravity.
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