Dark matter in spiral galaxies
Abstract
Studies of the rotational-velocity distribution in 60 spiral galaxies of morphological types Sa, Sb, and Sc and of different luminosities are reported and analyzed in terms of galactic mass/luminosity distribution and its implications for the expansion of the universe. Spectrographic images obtained with a photomultiplier tube on sensitized plates during 3-hour observations at the 4-m telescopes at Kitt Peak National Observatory and Cerro Tololo Inter-American Observatory were examined for Doppler-shift evidence of rotational velocity distribution across the visible disk of each galaxy. It was found that rotational velocity increases with radial distance from the galaxy center, a phenomenon best explained by a non-luminous spherical halo of matter extending beyond the visible galactic disk. This hypothesis can be seen as consistent with recent observations of the Milky Way, of AO 136-0801 (a faint galaxy consisting of a disk surrounded by a ring), and of pairs of galaxies. It is considered possible that such invisible galactic halos contain enough mass to increase the mass/luminosity ratio of the universe to near the 700 solar units theoretically necessary to brake the expansion of, or 'close', the universe.
- Publication:
-
Scientific American
- Pub Date:
- June 1983
- DOI:
- 10.1038/scientificamerican0683-96
- Bibcode:
- 1983SciAm.248f..96R
- Keywords:
-
- Dark Matter;
- Galactic Nuclei;
- Galactic Rotation;
- Mass Distribution;
- Spiral Galaxies;
- Doppler Effect;
- Emission Spectra;
- Galactic Mass;
- Galactic Structure;
- Kepler Laws;
- Luminosity;
- Velocity Distribution;
- Astrophysics