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Pushing Past Redshift Eight

No one has ever seen an object further away than the one at the center of the image below. It’s a gamma-ray burst known as GRB 090423, spotted by the Swift satellite on April 23rd and quickly observed by the Gemini Observatory and United Kingdom Infrared Telescope, both on Mauna Kea (Hawaii). The source is visible at longer wavelengths but disappears at the 1 micron level, all of which corresponds to a distance of about thirteen billion light years.


Image: The fading infrared afterglow of GRB 090423 appears in the center of this false-color image taken with the Gemini North Telescope in Hawaii. The burst is the farthest cosmic explosion yet seen. Credit: Gemini Observatory/NSF/AURA, D. Fox and A. Cucchiara (Penn State Univ.) and E. Berger (Harvard Univ.)

Spectacular, no? Numerous telescopes around the planet went on to observe the GRB’s afterglow, allowing the infrared light’s spectrum to confirm the highest redshift ever measured: z = 8.2.

The object in question was probably a massive star reaching the end of its life, its core collapsing into a black hole or neutron star. In the process, jets of gas punch out of the star and encounter gases previously shed during the star’s senescence, heating them up to produce the short afterglows that can be seen in various wavelengths. The visible light of the event was absorbed by hydrogen gas in the early universe, but the infrared glow was bright indeed, given that the light we see in the image has been traveling for most of the 13.7 billion year age of the universe.

Edo Berger (Harvard Smithsonian Center for Astrophysics) notes the significance of the find:

“I have been chasing gamma-ray bursts for a decade, trying to find such a spectacular event. We now have the first direct proof that the young universe was teeming with exploding stars and newly-born black holes only a few hundred million years after the Big Bang.”

Take a look at this second image, which places the GRB in perspective.


Image: Distribution of redshifts and corresponding age of the Universe for gamma-ray bursts detected by NASA’s Swift satellite. The new GRB 090423 at a redshift of z = 8.2 easily broke the previous record for gamma-ray bursts, and also exceeds the highest redshift galaxy and quasar discovered to date, making it the most distant known object in the Universe. GRB 090423 exploded on the scene when the Universe was only 630 million years old, and its light has been travelling to us for over 13 billion years. Credit: Edo Berger (Harvard/CfA).

Comments on this entry are closed.

  • James M. Essig April 28, 2009, 18:28

    Hi Paul;

    This z = 8.2 gamma ray burst is truely remarkable. The fact that we can obtain an image of something as it happened when the universe was only 630 million years old is outstanding.

    It would be really cool if we could access infornation on nature before the birth our universe. If our universe is a cyclical big bang universe, to be able at some point to access some information from a previous cycle would be fascinating.

    I like to muze that in a sense, viewing cosmically remote objects is a form distant backward time travel.

  • bigdan201 April 28, 2009, 22:35

    it mustve been an enormous burst to be so visible from across most of space-time.. but it does fit with the idea that stars were much more massive and shorter-lived in the early universe.

    what are the other objects in the picture? quasars, stars, or galaxies?

    i used to wonder what it would be like to point a telescope to the earliest stages of the universe, or even at the big bang itself.. what would you see? i am aware, however, that there is some cosmic horizon which we cant see past, because light/electromagnetic waves from beyond the horizon havent reached us. im not sure exactly where this horizon is though, or whether different methods of observation could widen that horizon. itd be great to have a clear picture of the earliest stages of the universe.

  • Ron S April 28, 2009, 23:52

    James: “It would be really cool if we could access infornation on nature before the birth our universe.”

    Here’s a paper that tries to show how galaxy cluster velocities may provide info about what is ‘outside’ the observable universe:


    If you want to cut to their (speculative) interpretation, flip to page 8.

  • ljk April 29, 2009, 10:21


    GRB 090423: The Farthest Explosion Yet Measured

    Credit: Gemini Observatory / NSF / AURA, D. Fox & A. Cucchiara (Penn State U.), and E. Berger (Harvard Univ.)

    Explanation: An explosion so powerful it was seen clear across the visible universe was recorded in gamma-radiation last week by NASA’s orbiting Swift Observatory. Farther than any known galaxy, quasar, or optical supernova, the gamma-ray burst recorded last week was clocked at redshift 8.2, making it the farthest explosion of any type yet detected.

    Occurring only 630 million years after the Big Bang, GRB 090423 detonated so early that astronomers had no direct evidence that anything explodable even existed back then. The faint infrared afterglow of GRB 090423 was recovered by large ground telescopes within minutes of being discovered.

    The afterglow is circled in the above picture taken by the large Gemini North Telescope in Hawaii, USA. An exciting possibility is that this gamma-ray burst occurred in one of the very first generation of stars and announced the birth of an early black hole.

    Surely, GRB 090423 provides unique data from a relatively unexplored epoch in our universe and a distant beacon from which the intervening universe can be studied.

  • James M. Essig April 29, 2009, 13:05

    Hi Ron S.

    Thanks for providing the link to the paper. The science of observing if only by way of indirect evidence or other tell tale signs of what lies immeadiately beyond the boundaries of the observable universe is fascinating to me.

    One thing I like to consider is the possibility of truely stupendous massed blackholes that may reside out side our cosmic light cone, I mean really massive blackholes with the mass of the observable universe that would act in such a manner that they would have a stable event horizon that would not easily be stretched by the expansion of the universe.

    By the way, I often wonder what such gamma ray burst would do if they occured within 1,000 parsecs of Earth, especially if models suggesting that gamma ray bursts are narrow beams of gamma radiation with an angular divergence of about 1 degree or less.

    Given that the supergiant star Eta Carinae could go supernova at any time for all we know, there is perhaps some risk posed by this star going supernova to Earth. I would not ordinarilly think that a super nova a few thousand light years from Earth would pose a threat, but Eta Carinae is just such a massive star. It will probably be a very high end supernova to say the least. Studying gamma ray burst can help in risk assessment regarding Eta Carinae going supernova when it finally occurs.

  • mike haynes May 2, 2009, 17:25

    Could someone explain how the red shift of this GRB was determined?

  • Ronald May 4, 2009, 5:00


    from what I have understood, a ‘regular’ supernova explosion might pose a threat to an eartlike planet up to some 20 – 30 ly away, a hypernova up to a maximum of a few hundred (300 orso) ly.

    Since Eta Carinae is about 8000 ly away, I do not expect there would be any real hazard to earth, but quite a spectacular show for sure: it would be at least as bright as the full moon and visible even during the day.

  • bkandah June 5, 2009, 15:41

    Does anyone know the coordinates of GRB 090423. thanks bk.

  • ljk June 16, 2009, 10:03
  • ljk October 29, 2009, 17:25

    October 28, 2009

    More Observations of GRB 090423, the Most Distant Known Object in the Universe

    Written by Nancy Atkinson

    This image shows the afterglow of GRB 090423 (red source in the centre) and was created from images taken in the z, Y and J filters at Gemini-South and VLT (credit: A. J. Levan).

    On April 23, 2009 the Swift satellite detected a gamma ray burst and as we reported back in April, scientists soon realized that it was more than 13 billion light-years from Earth. GRB 090423 occurred 630 million years after the Big Bang, when the Universe was only four percent of its current age of 13.7 billion years.

    Now, continued observations of the GRB by astronomers around the world have yielded more information about this dramatic and ancient event: the GRB didn’t come from a monster star, but it produced a fairly sizable explosion.

    Full article and images here: