Into dark ages or again about GRB090423
Save This Post as PDFBack in April, I already wrote about GRB090423 – currently the most distant detected object in the Universe. Yesterday, two papers with details of mesurement have appeared in astro-ph (unfortunately, Icannot give you the links – see my comment below).
Let me remind you that currently the redshift of the most distant galaxy we observed is about 6.96, of the most distant quasar – 6.43 (redshift values are defined with very good precision), while the redshift of the most distant gamma ray burst (GRB090423) is about 8.3.
The value of the redshift in the latter case is determined by photometry measurements (photometry is not exactly the most precise method we have at our disposal) and from the Lyman-
absorption profile (which is much more precise method than photometry). Taking into account that both methods give the same value of the redshift (with corresponding error bars), we can consider the measurement as robust.
In usual Lambda CDM cosmology without any exotics redshift 8.26 corresponds to the age of the Universe 625 million years, and the very detection of the GRB shows that stars were already being born and dying at that time. It is interesting to note that parameters of GRB090423 are pretty much the same as of GRBs detected at lower redshifts – either the mechanics of GRB does not depend on the star much or there were already stars at that time that don’t differ too much from the ones we have today, at 
.
Via sergepolar.
Update: I realized after writing this blogpost that their paper, since it is submitted to Nature, is under press embargo, so I will remove the link to the paper. Honestly saying, I am not sure whether press embargo has any meaning in this particular case. First of all, the news was everywhere in press back in the end of April – for example, NewScientist made a video about it which is right now on Youtube and had about 65000 views already alone apart from its clones. Second, every dog in physics blogosphere (including your huble correspondent) has blogged about it.
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You mean, you cannot post any of these papers?
http://arxiv.org/abs/0906.1577
http://arxiv.org/abs/0906.1578
Yes, it seems so. Check out “Cosmic variance”, they have a rather nice discussion right now featuring one of Nature’s editors.