Space

GN-z11: Hubble Spots Furthest Galaxy Yet

A team of astronomers using the Hubble Space Telescope have discovered a surprisingly bright galaxy approximately 13.4 billion light years away, making it the most distant galaxy ever known.

When astronomers want to measure distances to the furthest galaxies they use spectroscopic data to determine a galaxies redshift. Redshift refers to the displacement of spectral lines toward longer wavelengths (the red end of the spectrum) in radiation from distant galaxies. The longer wavelengths are a signature of the extreme distances they’ve traveled. By studying the wavelengths and determining the redshift, researchers can extrapolate distance. GN-z11 has a redshift of 11.1, indicating a distance of 13.4 billion light years away, or just 400 million years after the big bang.

GN-z11-furthest-galaxy

A timeline of the universe with present day on the left and the big bang on the right. The two furthest galaxies are highlighted. Image credit: NASA/ Hubble/ Yale

GN-z11 is located in the constellation Ursa Major and was spotted in a Hubble Space telescope deep sky survey. It’s 25 times smaller than our Milky Way, containing just one percent of our galaxies mass in stars. It likely belongs to the first generation of galaxies and its discovery provides new insights into the evolution of the earliest galaxies.

“We see GN-z11 at a time when the Universe was only 3% of its current age,” said Dr. Pascal Oesch at Yale University, who is lead-author of a study to be published in the Astrophysical Journal.

Astronomers used the Wide Field Camera 3 (WFC3) aboard Hubble to obtain the necessary spectroscopic data to determine the redshift. Before this discovery, the most distant galaxy measured spectroscopically had a redshift of 8.68 (13.2 billion light years away).

“We pushed Hubble to its limits to get the spectroscopic data needed to determine the galaxy’s redshift, a measure of its distance from Earth,”said team member Prof. Garth Illingworth, of the University of California, Santa Cruz. “It’s amazing that a galaxy [like this] existed only 200 million to 300 million years after the very first stars started to form.”

Most distant galaxy

The remote galaxy GN-z11, highlighted in the inset, existed only 400 million years after the Big Bang, when the Universe was only 3 percent of its current age. Image credit: NASA/ ESA/ Yale University.

“It takes really fast growth, producing stars at a huge rate, to have formed a galaxy that is a billion solar masses so soon,” added Prof. Illingworth.

GN-z11s discovery had some astronomers scratching their heads, like Marijn Franx from the University of Leiden: “The discovery of GN-z11 was a great surprise to us, as our earlier work had suggested that such bright galaxies should not exist so early in the Universe.”

“The discovery of GN-z11 showed us that our knowledge about the early Universe is still very restricted. How GN-z11 was created remains somewhat of a mystery for now. Probably, we are seeing the first generations of stars forming around black holes.”

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