Editors' Choice

Science  17 Dec 1999:
Vol. 286, Issue 5448, pp. 1
  1. OVERLINE: A Quirky, Quiet Quasar – Jasny

    1. Barbara Jasny

    Quasars or quasi-stellar radio sources, are point-like sources of light that look like stars, but are the most energetic objects in the universe. One model to explain their extreme luminosity is a supermassive black hole at the center of the quasar. As the black hole feeds on another object or as two galaxies collide to form a black hole, an accretion disk of gas and dust forms around the black hole. Gravitational energy from the black hole heats the accretion disk, andthis thermal radiation is the energetic source of the quasar. The most distant quasars (with a high redshift) may represent the earliest objects formed in the universe, and observations of distant quasars should help solve the riddle of which formed first, black holes or galaxies.

    Fan et al. describe their discovery of an extremely luminous and very distant object. Astrometry and photometry carried out during the commissioning s tage of the Sloan Digital Sky Survey (http://www.sdss.org/)indicated that the object was a a redshift of about 4.62 and might be a quasar. Optical and radio spectra of the object obtained by the authors lead to a consistently mysterious set of characteristics. The object does not have broad optical emission lines like normal quasars, and it does not show any radio emissions, like radio-loud quasars or other possible radio-loud objects. Thus this early, bright beacon of the universe may represent a new type of quasar that is radiating its energy by a different process than the standard black hole model.–PDS

    Astrophys. J. 256, L57 (1999); http://arXiv.org/abs/astro-ph/?9910001

  2. OVERLINE: A Cooler Route to Nanotubes – Szuromi

    1. Phil Szuromi

    Carbon nanotubes can be generated on a surface through chemical vapor deposition. If part of a surface is covered with a transition metal catalyst such as iron or cobalt, simple hydrocarbons such as ethylene (C2H4) can decompose at high temperatures and form straight single-walled nanobutes growing normal to the surface. Dosa et al. have been exploring whether larger hydrocarbons with many double and triple bonds would react to form nonotubes at lower temperatures. These species reacted explosively however and yielded only a small fraction of carbon particles. Adding metal catalysts simply produced carbon soots. They now report that large unsaturated hydrocarboins that incorporate cobalt, nickel, or iron (complexed with carbonyl ligands) did react at relatively low temperatures (below 200) and prodced multiwalled carbon nanobutes with the metals trapped as particles withing nanotubes. Because numerous variants of these starting materials can be prepared, this lower temperature route may lead to greater synthetic control of nanotube fabrication.–PDS

    J. Am. Chem. Soc. 121, 10430 (1999)

  3. OVERLINE: Plant Responses to Climate Warming Change over Time – Hanson

    1. Brooks Hanson

    Carbon nanotubes can be generated on a surface through chemical vapor deposition. If part of a surface is covered with a transition metal catalyst such as iron or cobalt, simple hydrocarbons such as ethylene (C2H4) can decompose at high temperatures and form straight single-walled nanobutes growing normal to the surface. Dosa et al. have been exploring whether larger hydrocarbons with many double and triple bonds would react to form nonotubes at lower temperatures. These species reacted explosively however and yielded only a small fraction of carbon particles. Adding metal catalysts simply produced carbon soots. They now report that large unsaturated hydrocarboins that incorporate cobalt, nickel, or iron (complexed with carbonyl ligands) did react at relatively low temperatures (below 200) and prodced multiwalled carbon nanobutes with the metals trapped as particles withing nanotubes. Because numerous variants of these starting materials can be prepared, this lower temperature route may lead to greater synthetic control of nanotube fabrication.–BH

    Ecological Monographs 69, 491 (1999)