Like the rockers in “This Is Spinal Tap,” astronomers cranked the dials on the Hubble Space Telescope up to 11 to identify what they say is the farthest-out galaxy ever detected, from a time when the universe was a mere 400 million years old.
The light from the galaxy in the constellation Ursa Major, known as GN-z11, was sent out 13.4 billion years ago, astronomers report in a study to be published in the Astrophysical Journal. That light-year measurement surpasses the distances that were recorded for two faraway galaxies over the past year.
The researchers say this record is likely to stand until NASA’s next-generation James Webb Space Telescope comes online.
“We’ve taken a major step back in time, beyond what we’d ever expected to be able to do with Hubble,” Yale astronomer Pascal Oesch said in a news release.
Oesch and his colleagues had previously estimated GN-z11’s distance by determining its color in images from Hubble and NASA’s Spitzer Space Telescope. But now they say they’ve figured out the range more precisely, through detailed spectroscopic analysis of its light.
“Our spectroscopic observations reveal the galaxy to be even farther away than we had originally thought, right at the distance limit of what Hubble can observe,” said study co-author Gabriel Brammer of the Space Telescope Science Institute.
Astronomers measure extreme distances by checking how much the spectrum of a luminous object has been shifted toward reddish wavelengths, due to the expansion of the universe and the resulting Doppler effect. For GN-z11, the redshift measurement (known as z) amounted to 11.1, which translates to the time scale of 13.4 billion years. The redshift is reflected in the galaxy’s numerical name.
The number 11 strikes a chord with a scene from the “This Is Spinal Tap” mockumentary, in which a rock guitarist played by Christopher Guest explains that he can play louder than other bands because the dials on his amplifier go up to 11 rather than stopping at 10.
The galaxy looks like a reddish squiggle in the picture from Hubble’s Wide Field Camera 3, but that’s only because of the redshift. If we could have seen the galaxy up close, all those billions of years ago, it would be crackling with the birth of hot blue stars.
The research team says GN-z11 is 25 times smaller than the Milky Way and has just 1 percent of our galaxy’s mass in stars. But that size is still larger than astronomers would have expected for that era of cosmic history. The star formation rate is about 20 times higher than the Milky Way’s current rate, the researchers say..
“It’s amazing that a galaxy so massive existed only 200 million to 300 million years after the very first stars started to form,” said Garth Illingworth, an astronomer at the University of California at Santa Cruz. “It takes really fast growth, producing stars at a huge rate, to have formed a galaxy that is a billion solar masses so soon.”
The findings are whetting astronomers’ appetite for the Webb Space Telescope and other next-generation instruments such as WFIRST, the Wide-Field Infrared Survey Telescope. The Webb is due for launch in 2018.
“This new discovery shows that the Webb telescope will surely find many such young galaxies, reaching back to when the first galaxies were forming,” Illingworth said.
To learn more about GN-z11, join a live “Hubble Hangout” discussion with scientists at noon PT today.
