Quasars IV 
Quasars are the brightest long-lived objects in the universe — disks of superhot gas around giant black holes that shine billions or even trillions of times brighter than the Sun. And they’re some of the most distant objects that we can see — billions of light-years away. At such great distances, they remain “fixed” in the sky compared to the much-closer stars and planets. That makes them good signposts. In fact, scientists use them as a reference system that helps them study our own Earth.
Many quasars produce much of their energy in the form of radio waves. Astronomers use networks of radio telescopes to precisely map the positions of these quasars. About 300 radio quasars form a basic map that can be used to plot the positions of other celestial objects.
Because the quasars form such a stable background, they can also help study the motions of our own Earth, which wiggles and wobbles like crazy. The quasars allowed scientists to plot the motion of the north pole, for example, as well as the motions of Earth’s crust, and even tiny changes in the length of the day. The observations provided new information about Earth’s interior.
Today, quasars are helping improve the GPS system. Ultra-precise measurements of the positions of ground stations improve the accuracy of GPS time signals, which then provide even more detailed readings on Earth’s motions. So the distant quasars are providing valuable information about our own world.
Script by Damond Benningfield, Copyright 2012