Exploding Galaxies

Exploding Galaxies

One of the many exciting scientific discoveries of recent years was that certain peculiar-looking galaxies are intense sources of radio emission. Prominent in this respect is Cygnus A, the first discrete source to be discovered in the radio sky, and now identified with a faint optical object believed to be 500 million light-years away. Another strong radio source is Virgo A, identified with Messier 87. Photographs of the latter taken in short exposure-times reveal that a long, narrow jet extends from the galaxy’s central region. The jet probably consists of streams of high-energy electrified particles and presumably is responsible for the radio emission.

Similar jets are associated with other galaxies and indicate that these objects are in the throes of violent explosions. Perhaps the most spectacular case is the irregular galaxy Messier 82 in the Ursa Major, for there, if present interpretations are correct, we are witnessing the aftermath of an explosion of series of explosion which affected the entire nucleus. But since Messier 82 has an estimated distance of 10 million light-years, the events we now see took place 10 million years ago.

Messier 87, a short-exposure photograph showing the nuclear “jet”

Galaxies, like the stars in them, are moving objects. They have their own individual motions and, when considered as a whole or on the large scale, have motions away from us and from each other. The situation is somewhat similar to that of an expanding bun well-filled with raisins. As the bun expands the raisins move away from the center and also get further apart.. An insect on any one particular raisin would therefore get the impression that the other raisins were moving away from him. To make the model more apt, the individual raisins should be able to move about slightly, relative to the material of the bun, but they would still share in the overall expansion.