A fresh look at a tiny and distant patch of sky reveals what might be some of the first galaxies ever created. The surprisingly complex spiral structures look much like our own Milky Way Galaxy and must have taken shape earlier in the history of the universe than theory can account for, astronomers said.
The infrared observations of the Southern Hemisphere sky were made with the European Southern Observatory's 27-foot (8.2-meter) Very Large Telescope.
Astronomers were surprised that some of the galaxies, seen at very early stages in their development, are already about as big as the Milky Way is today. They exhibit the complex spiral structure typical of many modern-era, nearby galaxies that have had several billion years to evolve.
"We can see a new type of galaxy," said Marian Franx of Leiden Observatory in The Netherlands. "They were inconspicuous when observed in the optical, but they are very bright when observed in the infrared."
Surprisingly mature
The spirals are viewed as they were when the universe was less than 2 billion years old. The universe is estimated to be 12 billion to 15 billion years old now, so the light from these galaxies, while just captured from atop a high mountain in Chile, began its journey 10 billion to 13 billion years ago.
This sort of deep-field imaging allows astronomers to see the universe as it once was, but the number of photons that survive the journey are few. One hundred hours of observation time was required to collect the light that went into the final product.
Theorists had thought the first galaxies were probably spherically shaped, simple and able to mature quickly. Spiral galaxies were assumed to grow more slowly from smaller building blocks. Our galaxy, for example, evolved into its present shape through many mergers and acquisitions of smaller galaxies and star clusters.
Preliminary analysis also shows that the infrared galaxies are not very active in their rate of star formation, instead having already formed plenty of stars, a finding that contrasts with optical views of young galaxies.
"We can see no clear signs of star formation in newly identified galaxies," Franx told SPACE.com. "They may form stars," he said, yet "the regions of star formation may be obscured by dust. We cannot say yet on the basis of these images."
Because the galaxies are more mature than expected, they must have been building for quite some time and are probably among the oldest galaxies now known. However, they are seen from Earth as they were when still quite young.
The objects are the farthest ever photographed in the so-called Ks-band of the infrared spectrum, Franx and his colleagues said. Infrared is one type of radiation on the electromagnetic spectrum, which includes everything from radio to light and even X-rays. Infrared waves are longer than visible light waves.
Tiny patch of sky
The observations cover the same region of space looked at in a long-exposure, optical deep-field imaging campaign previously carried out by the Hubble Space Telescope. The patch of sky is just 1 percent of the area filled by a Full Moon and is in the constellation Tucana.
Faraway galaxies that were barely detected in the optical, by Hubble, are resolved more finely in the new infrared view. Hubble was actually able to spot things slightly farther away and therefore a bit farther back in time. It saw nothing of the spirals from that early era, however.
Follow-up observations will be needed to sort out the true meaning of the new discoveries.
"We now need similar images of a considerably larger region of the sky," Franx said. "We will soon follow-up these first, tantalizing results with more observations of other sky fields."
The Leiden Observatory's Ivo Labbe contributed to the findings, along with a host of other researchers at various institutions. The results will be published in the Astronomical Journal.
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