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Monday, 6 November 2017

Astronomers observe one of the oldest galaxies in the universe

Astronomers-observe-one-of-the-oldest-galaxies-in-the-universeAstronomers have observed the second most distant dust-filled, star-forming galaxy in the cosmos. The galaxy was spotted using the Large Millimeter Telescope, the most powerful telescope of its kind.

The LMT is positioned at the top of Sierra Negra, the fifth tallest peak in Mexico, and jointly operated by the University of Massachusetts, Amherst and Mexico's National Institute of Astrophysics, Optics and Electronics.

The newly imaged galaxy was likely one of the earliest star-forming galaxies in the universe.


"The Big Bang happened 13.7 billion years ago, and now we are seeing this galaxy from 12.8 billion years ago, so it was forming within the first billion years after the Big Bang," Amherst astrophysicist Min Yun said in a news release. "Seeing an object within the first billion years is remarkable because the universe was fully ionized, that is, it was too hot and too uniform to form anything for the first 400 million years."

The results of the LMT's latest survey isn't so much a revelation as it is a realization of its potential.

"This result is not a surprise, because this is what the LMT was built to do," Yun said.

Yun and his colleague published their discovery in the journal Nature Astronomy.

Because the distant galaxy is so obscured by dust, it is impossible to see in the visible light spectrum. VLT is designed to absorb only radio waves from a small portion of the light spectrum. The telescope has also been outfitted with instruments that help it measure redshifts.

"The way we can tell this object is very distant is by measuring its redshift, which is a measure of the universe's expansion speed," Yun said. "More distant objects have a larger redshift. To measure redshift, you use a spectral line of atoms or molecules, each of which has a recognizable, discrete signature or fingerprint."

The redshift among the spectral lines of carbon monoxide helped astronomers spot the ancient galaxy, dubbed G09 83808. Scientists confirmed their discovery and improved the accuracy of their observations with a follow up survey of the galaxy using the Smithsonian Submillimeter Array telescope located on Mauna Kea, Hawaii.

The discovery of G09 83808 was also assisted by gravitational lensing. The light from the distant galaxy was bent around another large galaxy on its 12.8 billion-year journey to Earth, effectively magnifying the light ten-fold.

Though already extremely powerful, LMT is still being built out. The telescope will be even more powerful upon its completion in a couple months. Researchers hope the latest discovery is just a sign of what's to come.

"It could be that there are a whole bunch of them out there and we haven't been able to see them, but with the LMT we have the power to see them. Maybe they'll start popping out," Yun said. "We are in the discovery field. Every time I reduce one of these data sets I'm full of anticipation. I'm always hoping that these things will pop out. You have to be a hopeless optimist to be doing this kind of work, and this time it absolutely paid off."

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