Most Distant Object Ever Seen

by Nancy Atkinson on April 27, 2009

Artists concept of a gamma ray burst. Credit: UC Berkeley

Artists concept of a gamma ray burst. Credit: UC Berkeley


According to the Sky and Telescope blog, NASA’s Swift satellite captured a faint gamma-ray burst (GRB) last Thursday which has smashed the record for the earliest, most distant known object in the universe. Various ground-based telescopes following up on Swift’s initial detection of the GRB have measured redshifts of the object, varying from 7.6 to 8.2. Whatever the final determination is of how much this GRB’s afterglow has been redshifted by the expansion of the Universe, it will set a record. In September 2008, Swift captured GRB 080913, the most distant gamma-ray burst ever detected, with a redshift of 6.7. Astronomers using the Very Large Telescope in Chile have determined that this current GRB (090423) went off about 600 million years after the Big Bang.

A GRB comes from the cataclysmic explosion of a massive star, which could signal the birth of a black hole, a collision of two neutron stars or some other unknown phenomenon. These bursts occur approximately once per day and are brief, but intense, flashes of gamma radiation. They come from all different directions of the sky and last from a few milliseconds to a few hundred seconds.

Since the Swift satellite was launched in 2004, it has undoubtedly seen GRBs with even higher redshifts, but many bursts have afterglows so faint that astronomers are unable to determine their redshifts. The most distant galaxies with well-measured redshifts are in the 6’s.

NASA is supposed to issue a press release with more information later today, and we’ll provide an update at that time.


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  • Nereid

    @BeckyWS: “Fingers of God” refers to long, thin lines of points (which represent individual galaxies) that point back to us (the Milky Way) when you draw a (radial) graph of galaxies’ redshifts against their position on the sky.

    This webpage, from a UCLA Berkeley astronomy course, illustrates the effect: http://astro.berkeley.edu/~louis/astro228/redshift.html

    In a cluster of galaxies, the individual galaxies will have a component of their velocity (the line of sight one) that varies a great deal about the mean (average) for the cluster as a whole; the paper by Hubble that I mentioned in an earlier comment discusses this dispersion, and concludes per the para I quoted. Note that the term, Fingers of God, was not invented until well after Hubble had died.

    Re Arp: are you familiar with ADS? It’s a wonderful tool for finding the published work of scientists, especially astronomers. When you put “Arp, H.” as author in the search field, it returns >400 entries! Now not all of them are papers published in relevant peer-reviewed journals of course, and it may be that there’s another H. Arp; however, I think it’s fair to say that he has had no difficulty getting his papers published. Further, he has a position at the highly respected Max-Planck-Institut für Astrophysik; hundreds of astronomers would just die to be so shunned by the research community.

    His idea about quasars being expelled from the nuclei of (active) galaxies is quite dead, as science. Perhaps the simplest way to show how dead the idea is is to start with the recognition that many classes of astronomical object are simply different manifestations of the same thing: active galactic nuclei (AGNs): quasars, QSOs, blazars, BL Lac objects, Seyferts, LINERs, … Quite a few (>100?) quasars have been found lensed (gravitationally) by foreground galaxies, and these objects can be studied to get direct, independent estimates of their distances. They are all at distances consistent with their redshifts.

    So, logically, the Hubble relationship is a highly reliable means of estimating distances (for objects outside the Local Group, and the Virgo cluster), OR quasars are a heterogeneous class (some are truly distant, some not), OR every method of estimating extra-galactic distances is hopelessly flawed (if you can think of some other logical conclusions, please share them!).

    Initially Arp tried to show that the lensed quasars were not, in fact, lensed, but as more and more were found it became harder and harder to make this kind of case.

    Curiously, as far as I know, no one tries to make the case that quasars, and AGNs in general, are a heterogeneous class, and only crackpots try to argue that all methods of estimating extra-galactic distances are fatally flawed.

    I hope this short summary helps.

    PS: I think I’ve tracked down what Hubble was referring to in his 1947 PASP paper; I’ll write it up later.

  • BeckyWS

    @ Nereid

    Wow thanks so much for taking the time to explain all that, it really helps it make a bit more sense to me why Arp came up with the theory originally and why it’s no longer relevant.
    I’m not sure either why Patrick Moore thinks working at Max Planck is somehow being rejected, I was just wondering if he was talking about his personal opinion or if there was actually any real debate about it.
    AGNs and the way they can all look different depending on angle etc is one of my favorite things about astronomy :)

    Thanks again
    Becky

  • Nereid

    To keep anyone who’s following this informed: I wrote a lengthy comment on what I found regarding what Hubble was referring to in his 1947 PASP paper that Total Science mis-quoted. That comment is “awaiting moderation”.

    In the meantime, a sound-bite summary: an enormous amount of research since 1947 has shown that the specific concerns Hubble was hinting at (“If they are valid,”) do not in any way suggest that the Hubble distance-redshift relationship is invalid.

  • Nereid

    My comment is still awaiting moderation.

    So let’s see if I can get it up, by breaking it into smaller pieces, with no more than one URL per piece.

    Part 1
    ===================================
    OK, here’s what I found wrt the 1947 PASP Hubble (mis-)quote by Total Science.
    If you apply General Relativity (GR) to a homogeneous, isotropic universe which is not ‘empty’ (i.e. it has mass-energy), you find only two stable solutions: expanding and contracting; and for ‘low’ redshift, observers like us should see a linear Hubble relationship.
    However, in GR ‘distance’ is a rather tricky thing; you can estimate the distance to an object in an expanding universe in several different ways – ‘luminosity distance’, ‘angular diameter distance’, ‘co-moving distance’, and so on. This webpage gives a good summary: http://www.atlasoftheuniverse.com/redshift.html

  • Nereid

    So far, so good.

    Part 2
    ===================================
    However, if we do not live in an expanding, GR universe, but one with flat, Euclidean geometry, all distances will be the same.
    So an independent test of an expanding, GR universe model might be to see if luminosity distances and angular diameter distances and … are consistent.
    And that’s what Hubble seems to be referring to, as you can see for yourself by reading this Hubble 1936 ApJ paper, and this Hubble 1942 Science one (my thanks to BAUT Forum’s dgruss23 for finding these):
    http://adsabs.harvard.edu/abs/1936ApJ….84..517H

  • Nereid

    Continuing.

    Part 3
    ===================================
    http://adsabs.harvard.edu/abs/1942Sci….95..212H
    His, and others’, attempts to use galaxy number-magnitude relationship were fraught with systematics, not least of which was the ‘K correction’; however, by 1947 there seemed to be some hints in the data that we may not live in an expanding, GR universe, and that’s what he refers to in his 1947 PASP paper.
    Since 1947 a great deal of research has been done, and the magnitude and redshift limits extended far, far beyond what Hubble and colleagues could reach in 1947 or 1953, and the GR-based models of the 1930s and 1940s became today’s consensus LCDM ones.
    ===================================

    The end.

  • Nereid

    OK, the ADS links didn’t copy correctly; here is the first one (1936 Hubble paper):
    http://adsabs.harvard.edu/abs/1936ApJ….84..517H

  • Nereid

    The second (1942 Hubble paper):
    http://adsabs.harvard.edu/abs/1942Sci….95..212H

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