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:
“Amour is the one human activity of any importance in which laughter and pleasure preponderate, if ever so slightly, over misery and pain.”
—Aldous Huxley (1894–1963)
“The teacher must derive not only the capacity, but the desire, to observe natural phenomena. In our system, she must become a passive, much more than an active, influence, and her passivity shall be composed of anxious scientific curiosity and of absolute respect for the phenomenon which she wishes to observe. The teacher must understand and feel her position of observer: the activity must lie in the phenomenon.”
—Maria Montessori (1870–1952)
“History does nothing; it does not possess immense riches, it does not fight battles. It is men, real, living, who do all this.... It is not “history” which uses men as a means of achieving—as if it were an individual person—its own ends. History is nothing but the activity of men in pursuit of their ends.”
—Karl Marx (1818–1883)