Number 160 (Story #2), January 14, 1994 by Phillip F. Schewe and Ben Stein|
GALAXY M81 LACKS DARK MATTER. The very idea of dark matter arose partly to explain the velocity profile of matter swirling around spiral galaxies. In many such galaxies the velocity of objects (determined by the doppler shift of their light emissions) seemed to be nearly constant as a function of the distance out from the center of the galaxy. Such a distribution would not occur, many scientists believed, unless a considerable amount of nonluminous matter were present in or near the galaxy. But new measurements of the neutral hydrogen in galaxy M81, made with the Very Large Array radio telescope, indicate that the velocity of hydrogen falls off with radial distance from the galactic center, a distribution suggesting a lack of dark matter. David Adler of the National Radio Astronomical Observatory and David Westpfahl of the New Mexico Institute of Mining and Technology said that these results, announced at the AAS meeting, demonstrated that dark matter is not distributed in uniform amounts among galaxies.