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ASTRO: Distances can be deceiving -- answers



 
 
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  #1  
Old June 20th 08, 07:21 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Default ASTRO: Distances can be deceiving -- answers

Galaxies
2: SDSS J105205.52+362836.3 magnitude 17.9 33 million light years
4: PGC 2081645 magnitude 17.1 Distance 563 million light years
5: SDSS J105133.55+363053.3 magnitude 17.9 570 million light years
6: SDSS J105141.30+363653.4 magnitude 16.1 570 million light years
1: SDSS J105243.56+362925.6 magnitude 17.9 1.676 billion light years
3: SDSS J105203.05+363205.0 magnitude 18.9 2.786 billion light years

QSOs
8: CSO 295 magnitude 16.8 5.66 billion light years
7: SDSS J105158.68+364326.1 19.0 magnitude 7.321 billion light years
9: SDSS J105242.50+364335.7 19.3 magnitude 8.09 billion light years

How many did you get right?

Rick

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Third character is a zero rather than a capital "Oh".

  #3  
Old June 23rd 08, 09:22 PM posted to alt.binaries.pictures.astro
Stefan Lilge
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Default ASTRO: Distances can be deceiving -- answers

Nice idea Rick. I would have guessed that number 6 was the 33 mly galaxy.
Quite wrong.
The great thing is that your image allows for a classification of even the
smaller galaxies. Numbers 4 and 5 are clearly spiral galaxies, which means
that they can't be dwarfs and should be at comparable distances. Number 2
doesn't have a spiral structure, so it was a candidate for a dwarf.

Stefan


"Rick Johnson" schrieb im Newsbeitrag
om...
Galaxies
2: SDSS J105205.52+362836.3 magnitude 17.9 33 million light years
4: PGC 2081645 magnitude 17.1 Distance 563 million light years
5: SDSS J105133.55+363053.3 magnitude 17.9 570 million light years
6: SDSS J105141.30+363653.4 magnitude 16.1 570 million light years
1: SDSS J105243.56+362925.6 magnitude 17.9 1.676 billion light years
3: SDSS J105203.05+363205.0 magnitude 18.9 2.786 billion light years

QSOs
8: CSO 295 magnitude 16.8 5.66 billion light years
7: SDSS J105158.68+364326.1 19.0 magnitude 7.321 billion light years
9: SDSS J105242.50+364335.7 19.3 magnitude 8.09 billion light years

How many did you get right?

Rick

--
Correct domain name is arvig and it is net not com. Prefix is correct.
Third character is a zero rather than a capital "Oh".



  #4  
Old June 24th 08, 06:40 AM posted to alt.binaries.pictures.astro
Rick Johnson[_2_]
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Default ASTRO: Distances can be deceiving -- answers



wrote:

Rick Johnson wrote:



wrote:

Rick Johnson wrote:




7: SDSS J105158.68+364326.1 19.0 magnitude 7.321 billion light years



How can something 7 billion light years away show up that big on an
image?

Rick


You are right. I flipped 7 and 8 in the answer. Got my eyes crossed
apparently. This is what it should have read.

QSOs
7: CSO 295 magnitude 16.8 5.66 billion light years
8: SDSS J105158.68+364326.1 19.0 magnitude 7.321 billion light years
9: SDSS J105242.50+364335.7 19.3 magnitude 8.09 billion light years

Sorry for the error.

Size is a function of brightness. The brighter the more scattered light
is recorded and thus the larger a point source appears. Now if I was
atop a mountain with great laminar air flow it would be a lot smaller.
Such mountains are hard to come by in Minnesota.

Rick




Actually, what I meant to say was how could it show up that big in
"your" image. Regardless of how I screwed up my question, that is one
bright object for something at such a distance.

Eight and nine are almost the same magnitude at almost one and one
half billion years difference in distance and visually look the same
in your image. There's a big difference between seven and eight at
roughly the same difference in distance as eight and nine in the
image.

It's a great image. I just don't understand how one object in the
same image can be, how do I say this, so distorted?

Rick


I don't see the distortion you mention. There happen to be three
quasars in the this part of the image (more in the part cropped out).
All look the same to me other than some are brighter than others due to
distance and "food supply". None are out of line with the norm. The
one you refer to is just a point source of light at magnitude 19.3.
It's the most distant and the faintest, nothing odd in that. 19th
magnitude is certainly not bright (1/21,000,000th the brightness of a
1st magnitude star) and rather common for QSO's at that light travel
distance.

If you mean why can we see it at all at that distance, that is due to
the extreme brightness of quasars. They far outshine the galaxy they
are in. Hubble can often see the fuzz of a galaxy around a QSO at this
distance but it is very difficult to do, even for Keck, from below our
atmosphere. Though it can see some. All I can pick up is the QSO
itself. The period from about 5 to 10 billion years ago was the age of
quasars. Most are found in this range. A few are seen up to 2 billion
years ago but after that all we see are the various types of AGN (Active
Galactic Nuclei) such as Seyfert galaxies. Back when the universe was
much smaller and galaxy collisions common they fed a lot of gas and dust
to the black holes creating quasars. But now that they are rare and the
black holes have cleared out most of the matter near them they've faded
down to the level of the AGNs we see in today's universe.

Note that close quasar is 3C 273 and even at 2 billion light years it is
easily seen in a 6" telescope as it shines at magnitude 12.8. Though,
like all quasars its brightness can fluctuate depending on its "food
supply". It has been as bright as 11.7 and as faint as 13.2.


Rick

 




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