X-rays pass right through human flesh, making it possible to study what’s under the skin. But they don’t pass through the atmosphere — not very far, anyway. So to study what’s under the skin of X-ray-producing stars and galaxies, astronomers must loft their telescopes into space.
X-rays are important for diagnosing what’s happening in some of the most interesting objects and events in the universe. That includes the environments around black holes, the remnants of exploded stars, and brilliant flares from some of the smallest stars.
The first X-ray telescope was launched aboard a V-2 rocket in 1949. During its few minutes above the atmosphere, it measured X-rays from the Sun. The first X-ray source beyond the solar system was discovered in 1962. And since then, more than three dozen X-ray telescopes have been sent into space. The largest, Chandra X-Ray Observatory, turns 20 years old this year.
X-ray telescopes operate in a different way from optical telescopes, which use glass mirrors to gather starlight. X-rays would pass right through such mirrors. So in the X-ray telescopes that take pictures, the inside of the telescope’s barrel is coated with a substance that reflects X-rays. The X-rays glance off this “mirror” and into the instruments that measure them. That produces pictures of X-ray objects — some of the most interesting objects in the universe.
We’ll have more about X-ray astronomy tomorrow.
Script by Damond Benningfield