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Image of a bright quasarRadio Stars

Quasars are the brightest and most distant objects in the known universe. In the early 1960's, quasars were referred to as radio stars because they were discovered to be a strong source of radio waves. In fact, the term quasar comes from the words, "quasi-stellar radio source". Today, many astronomers refer to these objects as quasi-stellar objects, or QSOs. As the resolution of our radio and optical telescopes became better, it was noticed that these were not true stars but some type of as yet unknown star-like objects. It also appeared that the radio emissions were coming from a pair of lobes surrounding these faint star-like objects. It was also discovered that these objects were located well outside our own galaxy. Quasars are very mysterious objects. Astronomers today are still not sure exactly what these objects are. What we do know about them is that they emit enormous amounts of energy. They can burn with the energy of a trillion suns. Some quasars are believed to be producing 10 to 100 times more energy than our entire galaxy. All of this energy seems to be produced in an area not much bigger than our solar system.

Distant Lights

Typical light spectrumWe do know that quasars are extremely distant. In fact, they may be the most distant objects in the universe. They also have the largest red shift of any other objects in the cosmos. Astronomers are able to measure speed and distance of far away objects by measuring the spectrum of their light. If the colors of this spectrum are shifted toward the red, this means that the object is moving away from us. The greater the red shift, the farther the object and the faster it is moving. Since quasars have such a high red shift, they are extremely far away and are moving away from us at extremely high speeds. It is believed that some quasars may be moving away from us at 240,000 kilometers per second or nearly 80% the speed of light. Quasars are, in fact, the most distant objects to ever be detected in the universe. We know that light travels a certain distance in a year. Quasars are so far away that the light we see when we observe them has been traveling for billions of years to reach us. This means that quasars are among the most ancient objects known in the universe. The most distant quasars observed so far are over 10 billion light-years away. This means we are seeing them as they appeared 10 billion years ago. It is entirely possible that some or all of the quasars we see today may not even exist any more.

Accretion disk around a black holeWhat is a Quasar?

We still do not know exactly what a quasar is. But the most educated guess points to the possibility that quasars are produced by super massive black holes consuming matter in an acceleration disk. As the matter spins faster and faster, it heats up. The friction between all of the particles would give off enormous amounts of light other forms of radiation such as x-rays. The black hole would be devouring the equivalent mass of one Sun per year. As this matter is crushed out of existence by the black hole, enormous amounts of energy would be ejected along the black hole's north and south poles. Astronomers refer to these formations as cosmic jets. Another possible explanation for quasars is that they are very young galaxies. Since we know very little about the evolutionary process of galaxies, it is possible that quasars, as old as they are, represent a very early stage in the formation of galaxies. The energy we see may be ejected from the cores of these very young and very active galaxies. Some scientists even believe that quasars are distant points in space where new matter may be entering our universe. This would make them the opposite of black holes. But this is only conjecture. It may be some time before we really understand these strange objects.

Finding Quasars

Hubble Space TelescopeThe first identified quasar was called 3C 273 and was located in the constellation Virgo. It was discovered by T. Matthews and A. Sandage in 1960. It appeared to be associated with a 16th magnitude star like object. Three years later, in 1963, It was noticed that the object had an extremely high red shift. The true nature of this object became apparent when astronomers discovered that the intense energy was being produced in a relatively small area. Today, quasars are identified primarily by their red shift. If an object is discovered to have a very high red shift and appears to be producing vast amounts of energy, it becomes a prime candidate for quasar research. Today more than 2000 quasars have been identified. The Hubble space telescope has been a key tool in the search for these elusive objects. As technology continues to enhance our windows to the universe, we may one day fully understand these fantastic lights.