Infant Cosmos Was Already Elderly
At first, they weren’t sure it was real or they were just seeing things. Now, it’s inescapable. As far back as cosmologists can see, there were already mature galaxies. That’s the thrust of two papers in the July 8 issue of Nature1,2 and a commentary on them by Keck Observatory astronomer Greg Wirth3, who says in the subtitle, “The discovery of massive, evolved galaxies at much greater distances than expected – and hence at earlier times in the history of the Universe – is a challenge to our understanding of how galaxies form.” But then in his opening paragraph it’s hard to disentangle the optimism from the pessimism:
Over the past two decades, astrophysicists have been spectacularly successful in explaining the early evolution of the Universe. Existing theories can account well for the time span from the Big Bang nearly 14 billion years ago until the Universe began to cool and form the first large structures less than a million years later. But detailed explanations of how the original stew of elementary particles subsequently coalesced over time, to form the stars and galaxies seen in the present-day Universe, are still being refined. As they report on pages 181 and 184 of this issue, Glazebrook et al.1 and Cimatti et al.2 have discovered the most distant ‘old’ galaxies yet. But the existence of these objects at such an early epoch in the history of the Universe seems inconsistent with the favoured theory of how galaxies formed.
According to Wirth, these new studies provide the “first solid evidence” that “as far back as 10 billion years ago there were already many old massive galaxies,” and “it is clear that even the best models can’t fully explain the evolution of galaxies.” Do galaxies grow much faster than predicted in the hierarchical models, that assume they coalesced from smaller objects? Or did the stars in these galaxies form “in a substantially different way from our expectations”? We may have to wait a decade for the next generation of larger telescopes, he concludes.
Glazebrook et al. found that up to a third of massive galaxies formed within 3 billion years of the Big Bang. Cimatti’s team found four mature, fully-assembled, massive spheroidal galaxies at redshift 1.6 to 1.9. They remark, “The existence of such systems when the Universe was only about one-quarter of its present age shows that the build-up of massive early-type galaxies was much faster in the early Universe than has been expected from theoretical simulations.”
1Karl Glazebrook et al., “A high abundance of massive galaxies 3-6 billion years after the Big Bang,” Nature 430, 181 – 184 (08 July 2004); doi:10.1038/nature02667.
2A. Cimatti et al., “Old galaxies in the young universe,” Nature 430, 184 – 187 (08 July 2004); doi:10.1038/nature02668.
3Gregory D. Wirth, “Old before their time,” Nature 430, 149 – 150 (08 July 2004); doi:10.1038/430149a.
Back to the eyepiece; less interpretation, more observation. If you can’t explain the origin of galaxies or the stars they contain, and if observations are in conflict with the best models, don’t expect anyone to believe the bluff that “astrophysicists have been spectacularly successful in explaining the early evolution of the universe.” The student doesn’t get to grade his own paper. (Remember Bob? see 03/06/2003 headline.)
See also: Starbirth “shaky foundation” in the 03/31/2004 headline (“We don’t understand how a single star forms, yet we want to understand how 10 billion stars form”); “time for theorists to panic?” in the 01/23/2004 headline, and “instant galaxies” and 01/02/2004 headline. Remember the rabbi’s description of “convoluted theories” and “frantic flailings” in the 09/30/2003 editorial? It’s premature to declare success (see 06/18/2003 headline) when swallowing the theory du jour produces gastrophysics attacks (see 05/02/2003 headline). Maybe the missing ingredient in current models is information (see 08/14/2003 headline).