Tuesday | November 21, 2017
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Astronomers use Keck to see most distant galaxy

Astronomers using the W.M. Keck Observatory have discovered the most distant known galaxy.

The scientists, led by University of Texas at Austin assistant professor of astronomy Steven Finkelstein, published an article on the discovery in today’s issue of Nature.

The galaxy they observed was seen as it was about 13.1 billion years ago.

Astronomer Casey Papovich compared getting the image to sending a time machine to ancient Rome and taking a picture of that civilization. That’s the kind of image the Keck Observatory’s MOSFIRE can get of billions of years old, still-forming galaxies, said Papovich, an associate professor of astronomy at Texas A&M University. The image ends up being of something that is very old, but something that looks fairly young.

The idea, Papovich said, is to find the oldest objects possible, as well as get more information that could lead to discoveries about how our own galaxy, the Milky Way, was formed.

Scientists were able to calculate the galaxy’s age by determining how quickly it was moving away from our galaxy, Papovich said.

“The farther away a galaxy is, the faster it’s moving from us,” he said, adding this galaxy was moving away faster than any previously discovered galaxy, at a speed about 97 percent of the speed of light.

Scientists also used spectroscopy to measure the light wavelengths, which in turn provides information about the galaxy, Papovich said. The longer the distance, the more the light shifts to red. In this case, Papovich said, the light had shifted so far into the red it was infrared, so it was only visible by using MOSFIRE. That instrument, which Keck installed last year, is the most sensitive equipment of its kind and is best suited for making those kinds of discoveries using infrared light, he added.

The distance of the galaxy is important, Finkelstein said, but a few other things also stand out in this particular discovery. First, the galaxy has a much higher rate of star formation than the Milky Way. Its star formation rate is also about 30 times higher than the average rate.

Scientists making a discovery that shows that much of a deviation from the average rate may consider whether they’ve found a “weird” exception, but in this case, another Keck-assisted discovery of a distant galaxy in the neighborhood of this galaxy also showed signs of higher-than-average star formation.

The newly confirmed galaxy also has an abundance of metals, Finkelstein said.

“We can tell it has 20 to 40 percent the metal abundance of the sun,” he said. “It’s really interesting (the levels got) so high so fast.”

Those two discoveries raise new questions for scientists to answer. The big questions, Finkelstein said, are what makes a galaxy form for many stars and what causes a galaxy to build up that metal abundance.

He said scientists during this particular observation saw one galaxy of the 40 they looked for. They’ll also be looking to understand more about why that happened.