UT Astronomers Discover Most Distant Known Galaxy

UT Astronomers Discover Most Distant Known Galaxy

As the McDonald Observatory gears up to celebrate its 75th year as an internationally renowned scientific hub, astronomers at UT have yet another landmark discovery to be proud of: spotting and measuring the most distant galaxy ever found.

The galaxy, dubbed z8_GND_5296, was pinpointed after a research team led by UT assistant professor Steven Finkelstein selected it—and 43 others—for further review out of the more than 100,000 galaxies discovered by the Hubble CANDELS survey. Because of the speed at which light travels, the astronomers are able to see the galaxy just as it was 700 million years after the Big Bang—literally looking into the Universe’s past.

“We like to study how we came to be: humans, civilizations, society, galaxies,” Finkelstein says. “When you look back at distant galaxies, things look very different. How did they go from little bumps to big, beautiful spirals? By looking at galaxies far away, we can kind of play a movie of how the Universe was formed.”

With the help of the Keck I telescope in Hawaii, Finkelstein and his team were able to definitively confirm that Galaxy z8_GND_5296 is the farthest and earliest ever discovered using spectroscopy, or measuring how much a galaxy’s light wavelengths have shifted toward the red end of the spectrum as they make their way toward Earth—a phenomenon called redshift.

Galaxy z8_GND_5296 has the highest redshift every confirmed, indicating that it originated only 700 million years after the Big Bang (or 5 percent of the Universe’s current age of 13.8 billion years). The more distant galaxies we study, Finkelstein says, the closer scientists get to being able to study the Universe’s mysterious beginnings.

“It’s hard to make broad conclusions based on one galaxy, but this particular object is surprising,” he says. Case in point: the galaxy is forming stars extremely rapidly, at a rate of 150 times that of our Milky Way. Because the galaxy that previously held the distance record had a similarly high rate, researchers now know there are more regions of extreme star formation than previously thought.

Despite this incredible finding, however, Finkelstein was still perplexed.

“Though we observed 43 galaxies, we only detected one. We asked ourselves, ‘Why aren’t we seeing more?'” Finkelstein says. “There was still more for us to learn.”

This lack of detection may mean the team has zeroed in on what’s called the “Era of Re-ionization,” Finkelstein says, a time when the Universe made its transition from an opaque state to a translucent one. A wall of neutral hydrogen, which occupied the Universe in its opaque state, may be hiding more distant galaxies from the astronomers’ instruments.

The team’s findings will be published in the Oct. 24 issue of Nature. Further research will rely on the Giant Magellan Telescope in Chile’s Atacama Desert, which will have five times the light-gathering power of Keck. Construction on the telescope is set to start soon, and should be completed by 2020. UT is a partner on the project.

“You know, this distance record won’t stand forever,” Finkelstein says. “The last record was from just a year and a half ago. But when it does get broken again, I hope it’s by us.”

Above, an artist’s rendition of the newly discovered most distant galaxy z8_GND_5296. Courtesy V. Tilvi, S.L. Finkelstein, C. Papovich, and the Hubble Heritage Team.


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