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:
“Life is a series of diminishments. Each cessation of an activity either from choice or some other variety of infirmity is a death, a putting to final rest. Each loss, of friend or precious enemy, can be equated with the closing off of a room containing blocks of nerves ... and soon after the closing off the nerves atrophy and that part of oneself, in essence, drops away. The self is lightened, is held on earth by a gram less of mass and will.”
—Coleman Dowell (1925–1985)
“You must learn to be still in the midst of activity and to be vibrantly alive in repose.”
—Indira Gandhi (1917–1984)
“A constant smirk upon the face, and a whiffling activity of the body, are strong indications of futility.”
—Philip Dormer Stanhope, 4th Earl Chesterfield (1694–1773)