Black holes are the rock stars of the universe. They thrill us with their strangeness, and attract everything within reach, all the while keeping their private domains out of sight. What’s more, they appear to break all the rules and get away with it. No wonder they keep us curious! So what exactly is a black hole? In Einstein’s General Theory of Relativity, he conceived of space as being like a thin rubber sheet. If you place a heavy object on the sheet it makes a dent. The sun, the most massive object in our solar system, warps the space around it, making a small dent or gravitational well. Objects, as well as light, moving through space, curve towards more massive objects. In the case of a black hole, the object in space is so dense, and therefore has such powerful gravity that it sucks in all the light and matter that come near enough to it, never allowing them to escape. Surrounding a black hole is the event horizon, the spherical boundary beyond which nothing can escape. Within it all presently known laws of physics become meaningless. Black holes come in different sizes. Super-massive ones are found at the centers of many galaxies, including our own Milky Way, and have masses up to several billion times the mass of our sun. Smaller ones form as the result of the gravitational collapse of a star, and it is possible that very small black holes formed in the early universe. So, if black holes give off no light, how do we know they are there? We can infer their presence from their gravitational effect on nearby matter, for example by tracking stars orbiting a region of space that appears to be empty. If a black hole is surrounded by nearby dust, gas and stars, an accretion disk is formed that swirls around it. The black hole’s gravity is so great that it rips the stars to pieces and they are sucked into the hole. This rapid movement heats the stars’ gas to such high temperatures that it causes the black hole to emit powerful radiation in the form of rotating beams of energy. We call this a quasar, and see some of its radiation as light. Quasars can be about 100 times brighter than the combined brightness of all the billions of stars in a galaxy. So while a black hole itself cannot be seen its effects are dazzling.
For more on the wonders of the universe, join the Springfield STARS Club for a talk by guest speaker James van Luik, Professor Emeritus of philosophy of science at Columbia University who will present: Cosmic Theories of Everything: GUTs and TOEs. Prof. van Luik has advanced degrees from the University of Paris and Oxford. His publications range from theoretical physics and cosmology to poetry and novels. He currently teaches cosmology classes at the Amherst Senior Center. His talk for the Springfield STARS Club will be held on Tuesday, October 27th at 7:30pm in the Science Workshop next to the Planetarium at the Springfield Science Museum at the Quadrangle. Refreshments will be served, and the public is welcome free of charge.
Also at the Springfield Science Museum, the next Stars over Springfield will be held on Friday, November 6th at 7:30pm. Richard Sanderson, curator of physical science, will present “The Nights of Raining Fire: The Great Leonid Meteor Storms.” The public is welcome. Admission is $3.00 for adults and $2.00 for children 17 and under.
Amanda Jermyn, of Longmeadow, has been a member of the Springfield Stars Club since 2000 and currently serves on the club's board of directors. For more information, visit the Springfield Stars Club Web site at www.reflector.org or call 1(800)336-9054.
Copyright © Amanda Jermyn