“Seeing” a Black Hole
January 25, 2013
In a bold venture, a group of scientists is taking steps to make the first-ever image of an invisible black hole, one of the most mysterious objects in the universe. Their target is the black hole at the center of our own galaxy, the Milky Way. (Each of the billions of galaxies in the universe is thought to harbor a massive black hole at its center.) The group, led by Sheperd Doeleman of the Massachusetts Institute of Technology, plans to utiltize as many as 50 radio telescopes to do the job. The scientists will essentially turn the network of telescopes into one giant telescope the size of the Earth itself. They are calling this network the Event Horizon Telescope. Radio telescopes have been chosen for the job because, unlike other types of telescopes, they can “see through” the cloud of dust and gas that surrounds a black hole. The data from the telescopes will be fed into a computer, which will be used to create the image.
Black holes are regions of space whose gravitational force is so strong that nothing can escape from them–not even light. They are believed to be the remains of stars that died in massive explosions called supernovae. The black area around a black hole is known as the event horizon. Astronomers use the radius of the event horizon to specify the size of a black hole. No one has yet discovered a black hole for certain. The fundamental descriptions of black holes are based on equations in the theory of general relativity developed by the German-born American physicist Albert Einstein. The theory was published in 1916.
Scientists have never before imaged a black hole directly. The visual evidence for these objects comes from the behavior of other objects around them. The scientists hope to image the black hole to answer basic questions about them. For example, Einstein predicted that the event horizon is a perfect circle. If the black hole was slightly flattened or distorted from a perfect sphere in some way, Einstein’s theory would need to be revised or discarded. The measurements will be taken over several years using telescopes from around the world.
Additional World Book artices:
- Gravitational wave
- A Cosmic Assignment (a special report)
- The Search for Gravity Waves (a special report)
- Telescopes: 400 Years of Stargazing (a special report)
- The Universe on the Grand Scale (a special report)