I | | INTRODUCTION |
Dark matter is a still unidentified substance that makes up about 23 percent of the universe. It is thought to surround most galaxies, affecting their shapes by its gravity. Ordinarily it cannot be seen. This composite picture of galaxy cluster 1E 0657-556 was created from images taken by different space telescopes in X-ray and visible light. The cluster is actually two giant groups of galaxies that collided head-on. The dark matter around the groups of galaxies is indicated by the blue regions, which bend the light from more distant galaxies in the background. The pink regions are hot gas stripped away in the collision.
Dark Matter, in astronomy, designation for matter that does not give off or reflect detectable electromagnetic radiation, the radiant energy that includes visible light, radio waves, infrared radiation, X rays, and gamma rays. Although dark matter is practically invisible, astrophysicists have determined its existence by detecting its gravitational interaction with matter that does give off detectable electromagnetic radiation, such as stars, galaxies, and clusters of galaxies. Dark matter has become a vital component of modern theories of cosmology and elementary particle physics. Along with the phenomenon of dark energy, the puzzle of what dark matter is represents one of the most important questions in physics today.
II | | THE DISCOVERY OF DARK MATTER |
The existence of dark matter was first suggested in the early 20th century by the Swiss American astronomer Fritz Zwicky, but convincing and overwhelming evidence of its existence was gathered by the American astronomer Vera Rubin in the 1970s. In the early 1930s, Zwicky studied the rotational motions of thousands of galaxies clustered together in a large group of galaxies known as the Coma Cluster. He found that the orbital motion of the galaxies around their common center of mass could only be explained...