(Asked by Mike Kelly and Ben Foster)
Quasars
The term "quasar" is an acronym for quasi-stellar radio source. These objects tend to be bluish starlike structures that have very strong emissions in the radio band of the electromagnetic spectrum. They also have spectra that are highly red-shifted. These objects were first noted as intense radio sources in the 1950s, and in the 1960s astronomers noted that quasars had unidentifiable spectral emission lines associated with them. Of all objects in our universe, quasars exhibit the strongest red shifts.
The red shift associated with the spectra of quasars is due to an intense Doppler effect; this is the phenomena that takes place when a source of waves (in this case, light waves) is moving either towards or away from the observer. When moving towards an observer, the waves (from the observer's viewpoint) tend to "bunch up" causing the light to appear bluer than normal; if the source is moving away from an observer, then the waves "spread out" making the light seem redder than normal. These phenomena are called by astronomers blue- and red-shifting, respectively.
From an understanding of Hubble's Law and Doppler shifting, astronomers have determined that quasars are the most distant (and thus the oldest known, since light travels at a finite speed) objects in the universe, with the furthest being about 15 billion light-years (LY) from Earth. A light year is the distance that a ray of light travels (at 186,000 miles per second) in a single Earth year... roughly 6 trillion (or 6,000 billion) miles.
Quasars also have a reputation for being some of the most energetic structures
in our universe. Since they are so far away, and we receive their signals so
strongly here on Earth, some quasars are thought to emit more energy than 2000
galaxies combined together. This is a strange paradox considering that other
types of measurements have indicated that quasars are much smaller than ordinary
galaxies. Some theories for the cause of this massive energy output include
the possibility of quasars having super-huge black holes at their cores.
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