Do all galaxies have black holes at their centers? If not, what provides
the gravity to hold the galaxy together?
Joseph L. Heil
According to computer models and theory, it is not necessary for a galaxy to have a black hole at its center. The mass of the stars and gas clouds in the galaxy attracts and this gravitational attraction holds many galaxies together. This said, many, and probably most galaxies do have massive black holes at their center, including ellipsoidal galaxies and spiral galaxies with central bulges.
Rob Landolfi, Science Teacher, Washington, DC
'I beseech you to take interest in these sacred domains so expressively called laboratories. Ask that there be more and that they be adorned for these are the temples of the future, wealth and well-being. It is here that humanity will grow, strengthen and improve. Here, humanity will learn to read progress and individual harmony in the works of nature, while humanity's own works are all too often those of barbarism, fanaticism and destruction.'