Scientists Think They’ve Found Galaxies Way Out on the Edge
Scientists believe they have discovered galaxies that formed when the universe was but an infant, hidden in the dark sky much farther away than anything anyone has ever seen before.
Using technology that was developed for the military, a team of scientists from the University of Arizona searched a random patch of sky last spring to see if they could find distant galaxies that had been postulated but never seen.
According to some theorists, galaxies of forming stars should have been among the first objects in the universe; but if so, they would be so dim they would be nearly impossible to see, lying far beyond the quasars that until now have been the most distant objects ever found.
Theorists had speculated that early galaxies would emit radiation primarily in the infrared--heat--but that the intensity would be so low it could not be detected by telescopes as far away as the Earth.
But the military also uses heat detectors, and that technology recently became available to astronomers, allowing them to build instruments that would be thousands of times more sensitive than telescopes that had been available just a year ago.
When they used their new instrument for the first time on a mountaintop in Arizona, the team found two fuzzy patches that appeared to be about 17 billion light-years away. Since the universe is not believed to be much older than that, that would place the objects very close to the “big bang” that most believe marked the birth of the universe.
“We found two in a very small area of the sky,” said astronomer Richard Elston, who presented the results this week to the American Astronomical Society meeting here. The fact that two could be found in one small area also fits neatly with theory in that if galaxies did form that early, there should be plenty of them in deep space.
Elston, a doctoral candidate at the University of Arizona, hopes to prove that they are plentiful in the months ahead as more areas of the sky are searched, using the same infrared detector on bigger telescopes.
Although much confirmation by other teams will be required for the discovery to be authenticated, scientists warmed up to the announcement rather quickly, although many expressed caution.
“If it’s right, it’s pretty spectacular,” said UC Berkeley astronomer Hyron Spinrad, a leader in the search for distant objects.
What remains to be done could prove very difficult.
First, scientists must prove that the objects are as far away as the Arizona team believes. That conclusion would be based upon analysis of the color of the objects--the redder they are, the faster they are moving, and thus the farther away they must be. However, that process, known as the “red shift,” is subject to interpretation and the reliability of the data.
Beyond that, the scientists must prove that the objects are in fact galaxies and not just “some exotic infrared cloud,” a difficult challenge because the light is so dim that analysis of the objects’ chemical composition would be difficult even with more powerful telescopes.
‘Very Good Bet’
Patrick J. McCarthy, another UC Berkeley astronomer who has reviewed the Arizona results, said he is inclined to believe that the finding is valid.
“It’s a very good bet,” McCarthy said. “But it’s going to be truly difficult to prove it.”
McCarthy, who also specializes in deep-sky objects, said the discovery is important because it should help define the “epoch in which all galaxies formed.”
That, in turn, is important to understanding the evolution of the universe.
These galaxies, if that is what they are, formed about 17 billion years ago, which would make them the oldest objects ever discovered.
But since it has taken 17 billion years for the light to reach the Earth, they are seen as they were then, not now.
By filling in the gaps between then and now, scientists hope to piece together the process by which gases formed into stars and galaxies, and how galaxies interact to form the giant structures of the universe.
Heart of the System
Recent technological developments make that seem much more plausible today than just a few years ago, as the Arizona research illustrates.
The infrared camera used by the Arizona team was developed by Marcia Lebofsky Rieke of the University of Arizona. The heart of the system is a grid of more than 4,000 tiny heat detectors, supplied by the Rockwell International Science Center, mounted on an electronic sensor called a charged coupled device.
Unlike photographic emulsions used throughout astronomy in the past, these sensors capture nearly all the light that reaches the instrument. And since Rieke’s camera uses more than 4,000 detectors, it can do in a single night what would have required more than 4,000 nights with state-of-the-art technology available just a year ago.
That capability catapulted the Arizona team to the forefront of one of the most dynamic fields of astronomy today--the search for the universe’s most distant objects.
That search moved into high gear two decades ago with the discovery of quasars, highly energetic, starlike objects billions of light-years away. (A light-year is the distance light travels in a year, nearly 6 trillion miles.)