DNA and Pulsar Research Win 1993 Nobels
Lipkin, Richard, Science News
Methods that enhance the study of genetic material and the discovery of an unusual type of star garnered this year's Nobel Prizes in Chemistry and Physics.
In physics, Russell A. Hulse, 42, and Joseph H. Taylor Jr., 52, both at Princeton University, were cited for their discovery of a binary pulsar -- a pair of rotating neutron stars that has a illuminated the study of gravity waves in the universe. In chemistry, Kary B. Mullis, 48, formerly with Xytronyx Inc. in La Jolla, Calif., and Michael Smith, 61, at the University of British Columbia in Vancouver, will share the $825,000 prize for the powerful DNA research techniques each developed.
In 1974, Hule and Taylor used the 300-meter radio telescope at Arecibo, Puerto Rico, to monitor the beacon-like emissions of a pulsar. This stellar object, called PSR 1913+16, emits bursts of energy about 17 times a second with a steadiness comparable to that of the best atomic clocks. Noticing oddities in the pulsar's emission cycle -- believed at the time to be caused by one rapidly rotating neutron star -- Hulse and Taulor figured out that a second, companion star must be involved. In fact, the second star of this stellar system has one and a half times the mass of the sun compressed into a ball only 20 kilometers in diameter.
Moreover, by timing signals from the binary pulsar over many years, physicists have further verified aspects of Einstein's theory of general relativity. At a barely detectable level, the two stars are spiraling toward each other orbiting more quickly -- a rate change of only 75 milli-seconds per year. But the energy loss in the binary system is significant, falling in line with Einstein's predictions, if one assumes the pulsar emits gravity waves. Thus, many physicists see PSR 1913+16's behavior as good evidence for the existence of these otherwise unseen waves.
Smith's 1978 invention of oligonucleotide-based, site-directed mutagensis has enabled scientists to "reprogram" the genetic code by the changing the order of specific nucleic acid -- the building blocks of DNA. …