Astronomers say they’ve detected the most distant galaxy and estimate it’s roughly 30 billion light years away.
“It’s exciting to know we’re the first people in the world to see this,” says Vithal Tilvi, a Texas A&M University postdoctoral research associate and co-author of the paper in Nature. “It raises interesting questions about the origins and the evolution of the universe.”
The galaxy, known by its catalog name z8_GND_5296, fascinated the researchers.
Whereas our home, the Milky Way, creates about one or two Sun-like stars every year or so, this newly discovered galaxy forms around 300 a year and was observed by the researchers as it was 13 billion years ago.
That’s the time it took for the galaxy’s light to travel to Earth. A single light year, which is the distance light travels in a year, is nearly six trillion miles.
Because the universe has been expanding the whole time, the researchers estimate the galaxy’s present distance to be roughly 30 billion light years away.
“Because of its distance we get a glimpse of conditions when the universe was only about 700 million years old—only 5 percent of its current age of 13.8 billion years,” says Texas A&M astrophysicist Casey Papovich, who is second author of the study.
Hidden distant galaxies
Papovich notes that researchers are able to accurately gauge the distances of galaxies by measuring a feature from the ubiquitous element hydrogen called the Lyman alpha transition, which emits brightly in distant galaxies.
It’s detected in nearly all galaxies that are seen from a time more than one billion years from the Big Bang, but getting closer than that, the hydrogen emission line, for some reason, becomes increasingly difficult to see.
“We were thrilled to see this galaxy,” says Steven Finkelstein, an assistant professor at the University of Texas at Austin and the study’s lead author. “And then our next thought was, ‘Why did we not see anything else? We’re using the best instrument on the best telescope with the best galaxy sample.
“We had the best weather—it was gorgeous. And still, we only saw this emission line from one of our sample of 43 observed galaxies, when we expected to see around six. What’s going on?'”
The researchers suspect they may have zeroed in on the era when the universe made its transition from an opaque state in which most of the hydrogen is neutral to a translucent state in which most of the hydrogen is ionized. So it’s not necessarily that the distant galaxies aren’t there. It could be that they’re hidden from detection behind a wall of neutral hydrogen fog, which blocks the hydrogen emission signal.
Tilvi notes this is one of two major changes in the fundamental essence of the universe since its beginning—the other being a transition from a plasma state to a neutral state. He is leading the effort on a follow-up paper that will use a sophisticated statistical analysis to explore that transition further.
“Everything seems to have changed since then,” Tilvi says. “If it was neutral everywhere today, the night sky that we see wouldn’t be as beautiful. What I’m working on is studying exactly why and exactly where this happened. Was this transition sudden, or was it gradual?”
The Nature paper is the result of raw data gleaned from a powerful Hubble Space Telescope imaging survey of the distant universe called CANDELS, or Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey.
Source: Texas A&M University