Activity
Some main-belt comets display a cometary dust tail only for a part of their orbit near perihelion. Activity in 133P/Elst–Pizarro is recurrent, having been observed at each of the last three perihelia. The activity persists for a month or several out of each 5-6 year orbit, and is presumably due to ice being uncovered by minor impacts in the last 100 to 1000 years. These impacts are suspected to excavate these subsurface pockets of volatile material helping to expose them to solar radiation.
When discovered in January 2010, P/2010 A2 (LINEAR) was initially given a cometary designation and considered a member of this group, but P/2010 A2 is now believed to the remnant of an asteroid-on-asteroid impact. Observations of (596) Scheila indicated that large amounts of dust were kicked up by the impact of another asteroid of approximately 35 meters in diameter.
Read more about this topic: Main-belt Comet
Famous quotes containing the word activity:
“Genghis Khan, in his usual jodhpurs accessorized with whip, straddled a canvas chair and gloated upon the fairyland he had built. Journalists, photographers, secretaries, sycophants, script girls, and set dressers milled and stirred around him, activity ... irresistibly reminiscent of the movement of maggots upon rotting meat.”
—Angela Carter (1940–1992)
“The superstition respecting power and office is going to the ground. The stream of human affairs flows its own way, and is very little affected by the activity of legislators. What great masses of men wish done, will be done; and they do not wish it for a freak, but because it is their state and natural end.”
—Ralph Waldo Emerson (1803–1882)
“Who shall set a limit to the influence of a human being? There are men, who, by their sympathetic attractions, carry nations with them, and lead the activity of the human race. And if there be such a tie, that, wherever the mind of man goes, nature will accompany him, perhaps there are men whose magnetisms are of that force to draw material and elemental powers, and, where they appear, immense instrumentalities organize around them.”
—Ralph Waldo Emerson (1803–1882)