Distant Galaxies

The development of the radio telescope has led to two of the most important discoveries in modern astronomy: the identification of the most distant galaxies and the smallest stars ever seen. Before these discoveries were made, new large telescopes had to be built.

The most distant galaxies are called quasars. They were discovered in 1963 when astronomers noticed strong radio signals coming from small points in the sky. When the radio astronomer Maarten Schmidt from Mount Palomar Observatory looked at these points, he saw faint galaxies that could be seen only because they were shining brightly. These galaxies, or quasars, were the most powerful objects ever discovered, and are the most distant objects even seen. Some are over 13,000 million light-years away. They get their power from a huge black hole at their center.

A black hole is a region of space where the pull of gravity is so strong that even light cannot escape. When gas and dust fall into the black hole at the center of a quasar, they produce large amounts of light and heat. Although black holes are very small, they are extremely heavy. A black hole less than a centimeter across can weigh the same amount as the Earth. The black holes in the center of quasars may weigh up to 100 million times as much as our sun.