SEATTLE, Jan 9: The Hubble Space Telescope has looked back in time 13 billion years to the end of the dark age in the universe’s infancy, a period when stars finally began to shine, astronomers reported on Thursday.

The signal of the end of the cosmic dark ages is the detection of some 30 faint red objects by the orbiting telescope, according to Haojing Yan of Arizona State University.

Yan and his colleagues believe those objects are young star-forming galaxies seen when the universe was perhaps one-seventh its current size and less than a billion years old.

“This is the earliest that the Hubble Space Telescope has ever observed,” Yan said in an interview at a meeting of the American Astronomical Society.

In the so-called cosmic dark age, the ultraviolet light from the earliest stars was absorbed by neutral hydrogen. Only when significant numbers of stars were created did they heat up the hydrogen enough to keep it from blacking out their light.

The significance of finding dozens of those early objects was that a statistical study of them was now possible, Yan said.

Using Hubble’s new Advanced Camera for Surveys, the scientists detected the 30 young galaxies while examining a small part of the sky in the constellation Virgo where there are no known bright galaxies.

That made it easier to see the very faint distant early galaxies that heralded the end of the dark ages, the researchers said in statement.

The researchers estimated that at least 400 million of those objects filled the universe at that early stage.

In addition to the Hubble findings, researchers with the Sloan Digital Sky Survey reported the discovery of three distant quasars dating from about the same time.

Quasars are compact but luminous objects thought to be powered by supermassive black holes, those matter-sucking drains in space whose pull is so strong not even light can escape it.

The light from the oldest of the three ancient quasars took about 13 billion years to reach Earth from the constellation Ursa Major (the Big Dipper), the scientists said.

Because the quasars and early galaxies were detected at a time when the universe was small and young, their light has been stretched — its wavelengths lengthened — as the universe expanded. Longer wavelengths are redder and that phenomenon is known as red shift.

“Finding the rare, high-red shift quasars is a needle-in-a-haystack operation, made worse by the fact that a lot of the straw looks like needles in the first place,” Xiaohui Fan of the University of Arizona said. “That means that there are a lot of stars which look like high-red shift quasar candidates.”

The Sloan Digital Sky Survey aims to make a detailed map of one-quarter of the entire sky, determining the positions and brightness of 100 million celestial objects and measuring the distances to more than a million galaxies and quasars.—Reuters



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