When you start talking about cosmic measurements, most people have a hard time truly comprehending the figures involved. They become abstract, conceptual -- so much larger than any human experience.
So the age of the universe just seems like a number, but it's a very big number: roughly 13.8 billion years. That means the "edge" of the universe is 13.8 billion light-years away -- so far away that we've never been able to observe it.
But we're getting closer.
This latest breakthrough is something special: an ultra-luminous, light-blue galaxy known as EGS-zs8-1, located in the constellation of Boötes. It's now confirmed that EGS-zs8-1 is the oldest galaxy we've ever seen in the universe -- more than 13 billion light-years away, when the universe was only five percent of its current age.
A team of international astronomers, led by scientists at Yale University and the University of California Santa-Cruz, used data from NASA's Hubble and Spitzer space telescopes to identify the galaxy. Its distance was then calculated using the 10-metre Keck I telescope's MOSFIRE near-infrared multi-object spectrograph, at the W.M Keck Observatory in Hawaii.
Although it appears to be just 100,000 years old in images taken from the Hubble's CANDELS survey, the light received by Hubble is over 13 billion years old. It's possible that the galaxy as it currently exists has evolved into something unrecognisable. At the time it existed as seen in the images, though, it was already massive -- it's one of the biggest and brightest objects identified from the early universe.
"It has already grown more than 15 percent of the mass of our own Milky Way today," said Pascal Oesch, lead author of the study from Yale University. "But it had only 670 million years to do so. The universe was still very young then."
In fact, the galaxy was still in a rapid phase of starburst -- forming stars at about 80 times faster than the Milky Way is now.
EGS-zs8-1 is one of just a handful of early-universe galaxies whose age has been accurately calculated -- adding to the slowly growing bank of galaxies able to provide clues about how the very first generation of galaxies formed. During EGS-zs8-1's time, for example, the universe was changing, with the hydrogen between galaxies transforming from an opaque to a transparent state.
"It appears that the young stars in the early galaxies like EGS-zs8-1 were the main drivers for this transition, called reionisation," said study co-author, Rychard Bouwens of the Leiden Observatory, Leiden, Netherlands.
According to the data, early universe galaxies were very different from galaxies now. Although massive galaxies did exist back then, they were unusual colours -- such as EGS-zs8-1's pale blue -- originating, the researchers believe, from the very rapid formation of massive stars, interacting with primordial gases.
More information will be much more readily available with the launch of the James Webb Space Telescope in 2018.
"Our current observations indicate that it will be very easy to measure accurate distances to these distant galaxies in the future with the James Webb Space Telescope," said Garth Illingworth of the University of California, Santa Cruz. "The result of Webb's upcoming measurements will provide a much more complete picture of the formation of galaxies at the cosmic dawn."