I Unraveling the Mystery: The Composition of Quasars

[oliviaawheeler]

So what exactly are quasars made up of?

 

[DaveC426913]

"...a compact region in the center of a massive galaxy surrounding a central supermassive black hole.[4] Its size is 10–10,000 times the Schwarzschild radius of the enclosed black hole. The energy emitted by a quasar derives from mass falling onto the accretion disc around the black hole."

https://en.wikipedia.org/wiki/Quasar

 

[Stephanus]

Perhaps I can add.
Quasar, quasy stellar. It's from Latin. Thnigs like stars but not stars.
At first the astronomers thought they were stars, but further observations showed that they were not stars.

 

[newjerseyrunner]

Mostly hydrogen with some helium thrown in. Quasars existed in a time where heavier elements hadn't yet been produced in large numbers.

 

[Vanadium 50]

At first the astronomers thought they were stars

I doubt very much that this is true.

 

[PeterDonis]

I doubt very much that this is true.

It's true. Unlike distant galaxies, quasars appear pointlike in optical telescopes, so just looking at their visible appearance they are indistinguishable from very faint stars. These visible "stars" were apparently correlated with strong radio sources, but it was hard to be sure that the very faint visible "stars" were the same objects as the radio sources. It was only when astronomers realized that the spectra of these objects were highly redshifted that they became convinced they were something very different.

A good reference on the history is here:

https://arxiv.org/pdf/1304.3627.pdf

 

[Vanadium 50]

Interesting - Sandage's recollections/memoirs do not mention this at all. It's always "point like" or "quasi stellar", even before 1963 when the redshift was determined.

 

[Stephanus]

At first the astronomers thought they were stars, but further observations showed that they were not stars.

I doubt very much that this is true.

Actually I read that phrase from this
https://www.amazon.com/dp/B0006AY1WC/?tag=pfamazon01-20
In mid 1980, when I was in junior high.

I didn't know that the book was printed in 1962. I just know today. I don't know how much knowledge in astronomy has changed since 1980s, much less in 2016.

But there's a very interesting phrase from this

A good reference on the history is here:

https://arxiv.org/pdf/1304.3627.pdf

The discovery of quasars in 1963, and more generally, active galactic nuclei (AGN), revolutionized extragalactic astronomy. In early February 1963, Maarten Schmidt (b. 1929; Figure 1) ...

The book was printed in 1962.
The discovery of quasar is in 1963.
Either
- It's a second edition that I read
- The discovery of quasar not in 1963.
- My memory tricks me into thinking that I read that phrase from David Bergamini's book.

 

[Chronos]

Redshift is largely the only yardstick we have for the distant universe. While it has served us well and made many confirmed predictions that does not 'prove' it is invincible. But, without it we are lost in illusions of reality. We must either place faith in observational evidence or our ancient religious beliefs. I believe the former offers us a better future.