The first radio objects of this sort were scary because they appeared to be composed of unknown elements.
Maarten Schmidt figured out that it was the same elements, just redshifted. Whew!
But the redshift was so severe it meant that these objects were billions of light years away, yet as bright as stars in our own galaxy. Whoa!
But it couldn't be because they were so big. Since they varied in brightness so rapidly it meant they were only a few light days across. Less than a hundred times the size of our solar system.
We still don't know how something so small can be so bright, but super-massive black holes (billions of solar masses) might be the answer.
And then there are those magnetic line jets as seen in the radio, infrared, and visible portion of the spectrum.
Radio galaxies are those emitting radio waves as well as visible light. They are believed to have big black holes at their center.
Seyfert galaxies are spiral galaxies with extremely bright cores. Central black holes are also suspected here.
Active galaxies are all the galaxies with these unusual cores.
Thanks to the HST we can conclude that quasars are also centers of galaxies, although too bright for the likes of us to see the galaxy around them.
Active Galaxy Factors:
- amount of gas and dust in region surrounding the black hole
- black hole's rotation speed
- black hole's magnetic field strength
Quasars are a look back in time. None are near us. We might have had them way back when, too.
Because there isn't a spectrum for gamma ray bursts, we can't use redshifting to measure how far away they are. It took a burst observation followed by the observation of a very faint, very distant galaxy in the same spot to figure out they weren't coming from nearby.
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