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Astronomers discover most distant known galaxy

ScienceColleges and UniversitiesEducationAstronomy and AstrophysicsCornell UniversityUC RiversideUniversity of Texas at Austin

Just 700 million years after the big bang, our most distant known galaxy was a cauldron of star production, churning out new suns hundreds of times faster than our own Milky Way galaxy, scientists say.

But it was only this spring, roughly 13 billion years later, that astronomers first glimpsed evidence of this ferocious activity and confirmed the distance and age of the galaxy now designated as z8_GND_5296.

In a paper published Tuesday in the journal Nature, researchers said discovery of the galaxy suggested our early universe was capable of far more star production than previously believed.

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"Such a galaxy is unexpected," wrote lead study author Steven Finkelstein, an assistant professor of astronomy at the University of Texas at Austin. "The early universe may harbor a larger number of intense sites of star formation than expected."

Radiant energy, including visible light, travels no faster than 186,000 miles per second. Since it took that energy almost 13 billion years to travel from z8_GND_5296 to the W.M. Keck Observatory in Hawaii, researchers can only study the galaxy as it was in its infancy. 

It would appear very different if we were to glimpse its form in real time, scientists say.

"Such a galaxy would be very massive today and, having exhausted its supply of gas, would not be able to form many stars at the current time," said study coauthor Naveen Reddy, an assistant professor of astronomy and physics at UC Riverside. 

In order to determine the galaxy's age and distance from Earth, scientists study its so-called redshift, or the lengthening wavelengths of energy emitted by its stars over great distances. The higher the redshift, the greater the distance.

It's only recently, however, that technology has advanced to the point that high redshifts can be studied. In the case of z8_GND_5296, scientists used Keck's MOSFIRE, the Multi-Object Spectrometer for Infra-Red Exploration, for this purpose.

Dominik Riechers, an assistant professor of astronomy at Cornell University who was not involved in the galaxy study, said that the discovery of z8_GND_5296 may presage a new era of research into very distant galaxies. 

In an accompanying News & Views, Riechers noted that the James Webb Space Telescope will be able to detect similar galaxies with relative ease after its launch toward the end of the decade.

It's likely then that further galaxies will be observed.

Riechers notes that astronomers have confirmed the explosion of a massive and more distant star 70 million years earlier. However, due to the difficulty of detecting high redshift energy emissions, scientists have yet to link a galaxy with that tumultuous event.

The value of studying such distant galaxies, scientists say, is that it provides a window into the conditions of the early universe.

In particular, scientists said it could illuminate the period after the so-called cosmic dark ages, when the first stars and galaxies were formed and the neutral hydrogen that pervaded the universe became ionized. 

"Astronomy is a little bit like archeology ... as we dig deeper into the
sand, we are probing earlier periods in history," Reddy said. 

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