Leapfrogging backward in time, a group of astronomers reported on Tuesday that they had measured a bona fide distance to one of the farthest galaxies known, making it one of the youngest according to the Big Bang model of the universe.
The galaxy, more than a few billion light-years on the other side of the northern constellation Bootes, is one of the most massive and brightest in the early universe and goes by the name of EGS-zs8-1.
It is believed to have flowered into stardom only 670 million years after the Big Bang.
In this scenario, the light from that galaxy has taken 13 billion years to reach telescopes on Earth.
However, by now, since the universe has continued to expand during that time, the galaxy is about 30 billion light-years away, according to standard cosmological calculations.
Despite its relative youth, it is already about one-sixth as massive as the Milky Way, which is said to be 10 billion years old, and it is getting bigger, making stars 80 times faster than the Milky Way is making them today, according to the report in The Astrophysical Journal by Pascal Oesch of Yale University and his colleagues.
By the rules of an expanding universe, the farther away a galaxy is the faster it is retreating from Earth, measured by the redshift of its light being broadened to longer wavelengths, the way an ambulance siren seems to lower its pitch as it goes by.
In the past few years, as astronomers have raced one another into the past with instruments such as the Hubble Space Telescope, galaxies have been found that appear even more distant, but those measurements were just estimates based on the colors of the objects — so-called photometric redshifts.
The new galaxy stuck out in a survey of distant galaxies by the Hubble and Spitzer space telescopes known as CANDELS — Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey.
Its redshift was precisely measured with a powerful spectrograph known as MOSFIRE — Multi-Object Spectrometer for Infrared Exploration — on Keck 1, one of a pair of 10m-diameter telescopes on Mauna Kea in Hawaii.
That makes it the highest redshift confirmed in this way, said Garth Illingworth of the University of California, Santa Cruz, one of the astronomers who took part in the study.
“When it comes to redshifts, the Missouri motto of ‘show me’ comes to mind,” Illingwoth said.
“Even if one of us is pretty sure that our photometric redshift is good, astronomers want to see a spectrum, but that is really hard to do, even with Keck,” he said.
Knowing the distance allows astronomers to predict other properties of the galaxy, such as what kinds of stars are being formed in it and at what speed.
How galaxies were able to form and grow so rapidly after the lights came on in the universe is a mystery that might be addressed by a coming generation of instruments, such as the James Webb Space Telescope and the Thirty Meter Telescope, a goliath planned for Mauna Kea, already home to a dozen telescopes.
However, construction of the Thirty Meter Telescope, a US$1.4 billion project, has been halted due to protests by Hawaii residents, who say that their mountain has been abused.
An echo of the Thirty Meter Telescope controversy appears in the new paper, in which Oesch and his colleagues wrote: “The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.”
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