Slow down a minute."Braking news: Disks slow down stars" (SN: 8/12/06, p. 109) says that a magnetic linkage between spinning stars and the charged particles in the dusty disks that surround them slowed the spin of the stars, but says nothing about its effect on the disk. The law of conservation of angular momentum angular momentum: see momentum. angular momentum Property that describes the rotary inertia of a system in motion about an axis. It is a vector quantity, having both magnitude and direction. dictates that the angular momentum lost by the star would be transferred to the charged particles in the disk, presumably pre·sum·a·ble adj. That can be presumed or taken for granted; reasonable as a supposition: presumable causes of the disaster. raising their orbits around the star. Did the researchers comment on this or the potential effects that it might have on planet formation? JOHN A. BLACK JR., TEMPE, ARIZ ARIZ Arizona (old style) . Astronomer Luisa Rebull of the California Institute of Technology California Institute of Technology, at Pasadena, Calif.; originally for men, became coeducational in 1970; founded 1891 as Throop Polytechnic Institute; called Throop College of Technology, 1913–20. in Pasadena says that angular momentum is indeed being transferred from a star to its disk. However, she adds that her team, as a "humble observer," was concerned only with the effect on the stars.--R. COWEN |
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