Quasars and Active Galaxies
| Quasi-Stellar Objects, QSOs, or quasars are believed to be the most distant and luminous objects in the Universe. Quasars were discovered in 1963 as radio telescopes began to be able to pinpoint sources of radio waves more precisely. Observations of an occultation of the radio source 3C273 by the moon made by Cyril Hazard and colleagues showed that the position of the radio source was coincident with a 12th magnitude stellar object (about 250 times fainter than can be seen by eye, but bright by astronomical standards). |
 3C 273 - The "First" Quasar |
Normal stars like the sun are known not to be strong radio sources so 3C273 and other similar "radio stars" were dubbed Quasi-Stellar Radio Sources soon shortened to quasar.
The first spectrum of 3C273 was obtained by Caltech's Maarten Schmidt using the Palomar 200" telescope. Schmidt puzzled over the photographic spectrum for months before he recognized that the strong, broad emission lines in the star were the familiar hydrogen-Balmer series, but redshifted by 15%. See more here.
 Astronomer Maarten Schmidt in 1963 |
It was not the 15% redshift that had puzzled Schmidt. Galaxies were already known with much larger redshifts. It was rather the brightness of 3C273. 3C273 was a thousand times brighter than even a very luminous galaxy would appear at the distance (2 billion light years) corresponding to the redshift of 15%. What was this monster!!
Biggest puzzle from afar. How unlike the other ones, Brighter than a trillion Suns. Twinkle, twinkle, quasi-star, How I wonder what you are!  - George Gamow
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Strange connections
We now know Quasars belong to a much more diverse population of
strange objects, collectively termed, Active Galaxies.
Redshifts are measured in percent shift of wavelengths: above the redshift would be 0.15. The most shifted spectrum so far seen? A redshift, z, of 6.28! See its spectrum Here. z = (wavelength obs - wavelength at rest)/(wavelength obs) = 8800-1200/1200 = 6.3
