A European team of astronomers discovered the farthest-away galaxy ever, with light that began shining when the universe was only about 600 million years old.
The galaxy, UDFy-38135539, began forming when the universe, not yet transparent, was covered in a hydrogen fog that absorbed light from young galaxies, according to a report in tomorrow’s edition of the journal Nature.
The Big Bang that formed the universe, according to scientists’ prevailing theory, occurred an estimated 13.7 billion years ago. The newly discovered galaxy is the oldest object yet observed, according to the report. The finding may provide clues to how the universe organized itself into its current shape, said Malcolm Bremer, one of the study’s authors.
“We are seeing a very young galaxy at its very early stage of evolution,” said Bremer, a physics professor at the University of Bristol in the U.K., in a telephone interview. “It’s the first building blocks of the galaxies we see around us in the universe today.”
Finding the oldest galaxies such as UDFy-38135539 is difficult because their once-bright light now falls into the infrared part of the spectrum. The expansion of the universe over billions of years has stretched the light’s wavelength, according to scientists.
The object is one of several candidates that were identified when astronomers used the Hubble Space Telescope in 2009. The scientists then employed the European Southern Observatory’s Very Large Telescope in Chile to sort the light’s components and analyze it to determine the temperature, mass, luminosity and composition of the object that generated it.
After the Big Bang, the theory goes, the universe expanded and cooled, losing enough heat so that protons and electrons combined to form neutral hydrogen, which consists of a single proton orbited by a single electron. Neutral hydrogen is relatively opaque. At some point, electrons began to split off, forming ionized hydrogen, a substance that is relatively clear, allowing people to see the universe.
Galaxy UDFy-38135539 is from the period when reionization was taking place, Bremer said. The neutral hydrogen was probably changed by radiation from hot, bright stars in the first galaxies, and UDFy-38135539 may have been a source of that radiation, Bremer said.
Further research will center on finding similar galaxies from around the same epoch, Bremer said.
“All the work until now has been theoretical,” Bremer said. “We’re starting to fill in the details of the picture.”