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Farthest Visible Star

  1. Mar 12, 2006 #1
    What is the farthest visible star (observed by telescope) and what is the estimated distance?

    Thanks.
     
  2. jcsd
  3. Mar 13, 2006 #2

    chroot

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    That's sort of a nonsense question without being made a bit more precise. There are stars in our own Galaxy, and in other galaxies. We can resolve stars in most parts of our own Galaxy. (To "resolve" means to distinguish a single star from its neighbors.)

    We can obviously see stars in our own Galaxy's center; you can see them with your own eyes on a clear night.

    We can also resolve individual stars in other nearby galaxies. One of the most common ways to measure distance to other galaxies is to observe so-called "Cepheid variables," which have a distinct relationship between luminosity and period of variation.

    We can also "see" stars in millions of other galaxies, though we can rarely resolve individual stars.

    The furthest galaxies we can observe are the so-called quasars, which have redshifts up to about 7.0.

    - Warren
     
  4. Mar 13, 2006 #3

    -Job-

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    If we could see the light from every star that is being emitted at this very moment, rather than the light of stars that took ages to get here, would the sky look very different?
     
  5. Mar 13, 2006 #4

    Chronos

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    We cannot observe the light from every star being emitted at this very moment. The finite speed of light precludes that possibility.
     
  6. Mar 13, 2006 #5

    -Job-

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    I know that, i'm only wondering, if we could, whether it would look very different.
     
  7. Mar 13, 2006 #6
    Are there stars out there which light hasn't reach us yet because of being so far away?
     
  8. Mar 13, 2006 #7

    chroot

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    Of course, PatPwnt... probably untold trillions of them, but we'll never know unless we wait.

    On the other hand, the accelerating expansion of the universe indicates that the number of objects in the observable universe is actually decreasing with time.

    - Warren
     
  9. Mar 13, 2006 #8

    SpaceTiger

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    The stars would be of a different age (and some would be gone). The exact difference would depend on the star.
     
  10. Mar 14, 2006 #9
    Furthest star is UDF 00411 with a redshift of z=6.080000

    Furthest object is the galaxy(galaxy cluster?) ABELL 1835:[PSR2004] 1916 with a redshift of z=10.001750

    Its quite incredible to think that we can see a redshift of 10, astronomy has come so far, its very exciting.
     
    Last edited: Mar 14, 2006
  11. Mar 14, 2006 #10
    Job, yes the Universe would look much brighter if all starlight reached us without having to take light years to reach us. There was a thought experiment that reasoned that the Universe could not be infinite in expanse because the night sky would be perfectly lit up with no dark spaces if it were. However, this never considered the fact that light takes time to reach us, so in fact the Universe could be infinitely large and the stars we see today are remnants of light sent out long, long ago. Its strange to think that many of the stars we see in the sky do not exist anymore, since they could have easily novaed millions of years ago, but their light that we see was sent out billions of years ago.
     
  12. Mar 14, 2006 #11
    I can assure you the cluster Abell 1835 is not at redshift 10, it is at redshift 0.25, in fact I would wager good money that you won't find any clusters of this size above redshift 2 or 3. There was a paper reporting the detection of a redshift 10 galaxy lensed by Abell 1835, but a later deeper observation failed to detect signatures of a redshift 10 galaxy.

    see this paper for more;
    http://arxiv.org/abs/astro-ph/0412432
     
  13. Mar 14, 2006 #12

    Janus

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    The resolution of Obler's Paradox is not the fact that light takes time to reach us, but that the universe is expanding.
     
  14. Mar 15, 2006 #13
    matto



    Check this link, is it out of date or inconclusive?http://nedwww.ipac.caltech.edu/cgi-...zv_breaker=30000.0&list_limit=5&img_stamp=YES
     
  15. Mar 15, 2006 #14
    Janus

    My mistake.

    BUT consider this, an expanding Universe alone does not fully explain why the paradox is disproved. You still require the fact that light has a finite speed. For if light's speed was infinite, whether the universe was expanding or not would make no difference
     
  16. Mar 15, 2006 #15
  17. Mar 15, 2006 #16
    Looking at your "search" results but paying attention to the details it provided -- it says ABELL 1835 has a SPEED of 10.001750 km/s and a z= 0.0 (well within matt.o limit of 3). Best re-read your link; looks like an error in the search not the detail.
     
  18. Mar 15, 2006 #17
    No, it says ABELL 1835:[PSR2004] 1916 is at z=10, but you should read the references provided when you click on the "refs" link (there are 4).

    Just to be clear, Abell 1835 is the lensing cluster. It is lensing the proposed redhift 10 object called "ABELL 1835:[PSR2004] 1916".
     
  19. Mar 15, 2006 #18
    I see, the line I was trying to read is almost indecipherable the way it’s displayed.
    Plus I didn’t pick up that when you were talking about “Abell 1835” it wasn’t the same thing as the "ABELL 1835:[PSR2004] 1916" that Chaos had referenced.

    So the cluster that’s doing the lensing has a z= 0.25.
    The lensed (magnified) object in question behind it has the high z of 10.

    Not sure I know how to interpret the comments in the references. But is it basically that it’s not clear exactly what is being seen though the lensing effect, maybe even multiple images of the a few of the same stars (like an Einstein Cross)? And that whatever it is, it’s not like an organized galaxy?
     
    Last edited: Mar 15, 2006
  20. Mar 16, 2006 #19
    The references doubt its really an 'object' at z=10 as far as I could tell. If it is really an object I'd guess it would be a QSO wouldn't it? Sorry about the mixup about the lensing, I assumed it was known that Abell lensed the 'object' in question given the reference I provided.

    Anyone know the highest redshifted object confirmed? Is it a QSO?
     
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