Maybe you saw it in today's news: astronomers have broken the record for the farthest thing ever seen. It's the gamma-ray burst GRB 090423, seen to happen last April 23rd in Leo, with a redshift of about 8.1. That means its light has been travelling through expanding space for 13.1 billion years, and that the burst took place 630 million years after the Big Bang.

Burst afterglow

The fading infrared afterglow of GRB 090423 is circled in this infrared image taken with the Gemini North Telescope in Hawaii last April. The burst was the farthest, earliest cosmic explosion yet seen.

Gemini Observatory / NSF / AURA / D. Fox / A. Cucchiara / E. Berger

If that sounds familiar, it's because we reported the news last April; read it here. The journal Nature issued a press release about it today, which is why it's being treated as if it were breaking news.

The burst occurred around the end of the "Dark Ages" following the Big Bang, when the universe was lighting up with stars and quasars.

Interestingly, however, the burst turns out to have properties matching bursts occurring later. The very first stars ("Population III") are thought to have included many that were much more massive and brilliant than those that formed later, because the first ones were completely uncontaminated by the traces of heavy elements that make a star's interior less transparent. Such uncontaminated, supermassive stars might explode in their own type of gamma-ray burst — and indeed, the most ancient bursts do seem to be systematically more powerful, and perhaps of shorter average duration, than later ones.

On the other hand, wherever Population III stars started living their brief lives and dying, massive stars made of second- and later-generation material might quickly start forming and dying too.

The hunt for more record-breakers continues. Bursts out to redshift 20 or greater should be detectable with current technology.

Two research papers and a review article about GRB 090423 appear in the October 29th issue of Nature:. paper 1, paper , review article.

Nature also put out a video news release.


Image of Rod


October 29, 2009 at 10:17 pm

We should remember that the distance and age is model dependent parameters. Some other features that affect the interpretation of this GRB in cosmology are:

1. initial singularity for the origin of everything including physical law and physical constants in the universe, evolve from the cosmological singularity.
2. inflation solves problem of abundant magnetic monopoles by pushing into some other universe.
3. 1 second after big bang, universe is filled with primordial neutrinos.
4. The Cosmic Dark Ages exist for about 100 million years after the big bang.
4. 1st stars in the universe are Population III stars and form by a process quite different than M42 for example.
5. Dark energy and Dark matter evolve the universe.

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