Number 69, February 27, 1992 by Phillip F. Schewe and Ben Stein SUPERNOVA 1987A IS FIVE YEARS OLD . The brightest supernova in four centuries, SN1987A is now dimmer than its progenitor star, Sanduleak -69 202, but it still entertains astronomers. The lightcurve, long dominated by radiation from the decay of radioactive cobalt-56, may now be more dependent on radiation from the longer-lived isotope cobalt-57. Meanwhile a ring of gas surrounding SN1987A (at a radius of 0.68 light years) was illuminated (beginning in 1988) by light from the supernova. Measurements by the Hubble Space Telescope of the ring's angular diameter allowed the most accurate estimation yet of the distance between SN1987A and the Earth. Some scientists expect that the ring will brighten further when, around the turn of the century, the supernova shockwave itself reaches the gas ring. (Astronomy, Feb. 1992; Nature 20 Feb. 1992; New Scientist, 22 Feb. 1992.) ULYSSES HAS VAULTED PAST JUPITER and is now aiming to pass under the solar south pole in 1994. The first spacecraft to visit Jupiter in 12 years, Ulysses sampled the Jovian magnetic field, the strongest in the solar system. The magnetosphere was flatter than expected. Mission scientist Andre Balogh partly attributes this to the presence of a huge billion-ampere current flowing in the Io Torus, a sheet of sulphur an oxygen ions issuing from Jupiter's volcanic moon Io. (New Scientist, 22 Feb. 1992.) GRAPHITIC MICRO-TUBULES , the recently discovered structures consisting of concentric, hollow carbon needles, should possess a wide variety of conducting properties. Scientists at the NEC Corporation in Japan have performed calculations which show that the tubules, essentially one-dimensional objects, would behave like metals or like semiconductors depending on the diameter (typically a few nm) and the helical arrangement of the rolled carbon sheets forming the tubules. (Noriaki Hamada et al., Physical Review Letters, 9 Mar. 1992.) BLACK HOLE CANDIDATES are becoming more numerous. Besides the telltale bursts of x rays, the chief evidence for black-hole status seems to be the estimation of a mass of three or more solar masses for the unseen partner of a binary pair; this criterion rules out neutron stars, which must have lower masses. V404 Cygni, Nova Musca, and A0620 are the names of some the heavier contenders. None of these, of course, are in the same league with those million-solar-mass black holes suspected of living at the heart of certain active galaxies. (Astronomy, Mar. 1992; Science, 14 Feb. 1992.) POLARIZED BEAMS AND TARGETS for particle-physics experiments can often be achieved with the help of laser light. "One watt of laser light contains about the same number of photons as there are electrons in one ampere of current," according to Olin van Dyck of Los Alamos. Although the transfer of polarization from the photons in a polarized laser beam to electrons in, say, a photocathode, is inefficient, polarizations above 50% are common. Record-high proton polarizations of 78% have been achieved with this method at TRIUMF, the accelerator in Vancouver. (CERN Courier, Feb. 1992.)