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Early universe looked like
“vegetable soup,” researchers say
Posted March 11, 2005
Courtesy Nature
and World Science staff
What did the universe look like in its infanthood, when it was only 2 to 3 billion years old? Astronomers used to think it was a pretty simple place containing relatively small, young star-forming galaxies. Researchers now are realizing that the truth is not that simple.
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This artist's concept shows a warm, watery alien world in the early universe whose sky is filled with a variety of galaxies.
New data shows that the early universe was a big zoo with "animals" of all sorts, including surprisingly old, dead galaxies that stopped forming stars very
quickly, researchers say. The image on the front page shows one of the
actual images analyzed for the study. (Credit for above, David A. Aguilar
[CfA]; for front page image, Ivo Labbé)
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The early universe was as complex as today’s, researchers have found.
Studying the universe at this early stage is important in understanding how the galaxies near us were assembled over time.
Astronomers can see these early galaxies because their light takes so long to
reach us, we see them as they were long ago.
“It looks like vegetable soup! We’re detecting galaxies we never expected to find, having a wide range of properties we never expected to see,” said Jiasheng Huang of the Harvard-Smithsonian Center for Astrophysics.
The findings are reminiscent of other recent
results that show the overall, large-scale structure of the universe was already
in place early on (See Universe
matured early, March 2 World Science.) The new research adds to this picture
by showing that not just the large-scale structure, but the complexity was also
there.
“It’s becoming more and more clear that the young universe was a big zoo with animals of all sorts,” said Ivo Labbé of the Observatories of the Carnegie Institution of Washington, lead author of a study announcing the findings.
Using NASA’s Spitzer Space Telescope, the astronomers searched for distant, red galaxies in the Hubble Deep Field South-a region of the southern sky previously observed by the Hubble Space Telescope.
The images displayed about a dozen very red galaxies lurking at distances of 10 to 12 billion light-years. Those galaxies existed when the universe was only about 1/5 of its present age of 14 billion years.
“There’s as much variety in the early universe as we see around us today,” said Labbé. “Overall, we’re seeing young galaxies with lots of dust, young galaxies with no dust, old galaxies with lots of dust, and old galaxies with no dust.
The researchers said they were particularly surprised to find a curious breed of galaxy never seen before at such an early stage in the universe: old, red galaxies that had stopped forming new stars altogether. Those galaxies had rapidly formed large numbers of stars much earlier in the universe’s history, raising the question of what caused them to “die” so soon.
The unpredicted existence of such “red and dead” galaxies so early in time challenges theorists who model galaxy formation.
“We’re trying to understand how galaxies like the Milky Way assembled and how they got to look the way they appear today,” said Giovanni Fazio of the Center for Astrophysics, a co-author of the study. “Spitzer offers capabilities that Hubble and other instruments don’t, giving us a unique way to study very distant galaxies that eventually became the galaxies we see around us now.”
The study is to appear an upcoming issue of the scientific publication Astrophysical Journal
Letters.
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