Noe1 Crawford, age 12, of Nipomo, Calif., for his question:
What happens if two galaxies collide?
A collision of galaxies rocks the imagination. You would expect it to create the biggest bang in the universe and shatter billions of suns and their planets. There is indeed a big bang, but astronomers say that stars and solar systems are not annihilated in the cosmic collision.
The countless galaxies Of the cosmos are separated by vast distances. What's more, We are told that, the universe is expanding, and the spaces between the galaxies are increasing at fantastic speeds. A collision between two galaxies seems unlikely, but the rare event does occur. We can perhaps imagine the staggering event if We stretch our minds to grasp the dimensions of our own galaxy. If a spacecraft could maintain a speed of 70 million miles an hour, it could cross the big pinwheel in about 800,000 earth years.
The galaxy contains about 100 billion widely separated stars. The spaces between them are strewn with immense clouds of gas and cosmic dust. Our spacecraft might tangle with some of these cosmic clouds, but it would not be likely to crash into a star. It might come within range of a solar system perhaps once in several hundred years. Should our galaxy collide with another, the two systems would intersect with plenty of room for the stars.
But the interstellar gases would collide at fantastic speeds. This would create heat up to perhaps 100 million degrees, brilliant light and intense radio energy. In time the colliding galaxies would separate with no harm done to stars or planets. But much of the interstellar gas and dust would be swept away and perhaps left hove=ing in space between the separating galaxies.
Some years ago radio telescopes detected intense signals from the direction of the constellation Cygnus, the Swan. The source was finally tracked down and photographed by the 200 inch telescope. Two galaxies Were shown intersecting in a collision. Astronomical figuring showed that the event occurred 200 million light years away, and the big bang took 200 million years to reach us. We can assume that the colliding pair have long since parted and gone their separate ways.
Stars are nuclear powerhouses, and a collision between two stars would be disastrous. But the event is unlikely. Suppose there were only two cars in California. The chances of a collision between them would be as unlikely as one between two stars, even when a pair of galaxies meet and intersect each other.