dipper@utastro.UUCP (Debbie Byrd) (06/08/85)
Comets -- like lizards -- lose their tails and then grow new ones. More about comet tails -- after this. June 8 Tales of Comet Tails Comets such as Comet Halley are famous for their tails -- long luminous streamers of dust and gas coming out from the comet's head. The dust and gas form different types of tails -- both extending from the head of the comet in a direction generally opposite from the sun. DUST tails appear broad and diffuse as the tiny bits of dust are swept outward by the radiation pressure of sunlight. The PLASMA tail is usually more narrow and straighter than the dust tail -- and is made of the electrically charged particles of the gases released by the comet. The comet's plasma tail interacts with the solar wind -- also a plasma of ionized gases ejected continually from the sun. The solar wind carries with it the polarization of the sun's magnetic field -- which frequently reverses. The charged ions in the comet's plasma tail suddenly and abruptly face a solar wind with the opposite electrical charge. This interaction with the solar wind sometimes causes the comet to "lose" its tail -- with the tail breaking away from the comet's head to drift away into space. Then, like a lizard on Earth, the comet rapidly grows a new tail. In June of l910 -- photographs of Comet Halley showed the comet losing its plasma tail. This time around very detailed records will be made of the interaction of the solar wind and the tail of Comet Halley. Script by Diana Hadley. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin