An international team of astronomers has uncovered a unique ancient galaxy in our own cosmic neighborhood—just 240 million light-years from Earth—which has essentially remained unchanged for the past 10 billion years, according to a new study published on Monday in the journal Nature.
This galaxy—known as NGC 1277—is composed exclusively of aging stars, appearing just as it did in the early stages of the universe. Researchers said that at the beginning of its life, NGC 1277 was producing stars 1,000 times faster than our Milky Way today; however, this process abruptly came to an end.
Similar “relic galaxies” have been detected before—approximately one in every 1,000 is thought to be such a relic—however, none have been found so close to Earth. This presents astronomers with an unprecedented opportunity.
"We can explore such original galaxies in full detail and probe the conditions of the early universe," Ignacio Trujillo, an author of the study from the Instituto de Astrofísica (IAC) de Canarias, Spain, said in a statement.
The relic galaxy has twice as many stars as the Milky Way despite being just a quarter of the size, the results of the study show. This dense, compact agglomeration of stars is typical of galaxies in the early evolutionary stages, suggesting that NGC 1277 is trapped in a state of “arrested development,” the researchers from the IAC, the Max Planck Institute for Astronomy and Yale University said. Essentially, it has not accreted new material over time and so has stopped growing in size.
The researchers first started looking for relic galaxies using the Sloan Digital Sky Survey—one of the largest and most detailed astronomical surveys of the universe ever conducted. After identifying a number of promising candidates, they then used the Hubble Space Telescope to image the NGC 1277 in more detail.
They were able to confirm its status as a relic with the help of astronomical objects called globular clusters—large, compact and spherical collections of typically older stars orbiting a galactic core, usually in the outer regions of a galaxy.
Normally, massive galaxies have a mix of globular clusters: Some of these are low in metals—appearing blue—and others are metal-rich and appear red. Astronomers think that red clusters form in the early stages of a galaxy’s evolution, while blue clusters originate from smaller satellite galaxies merging with the massive galaxy.
However, NGC 1277 is almost completely devoid of blue globular clusters.
"I've been studying globular clusters in galaxies for a long time, and this is the first time I've ever seen this," Michael Beasley, also from the IAC, said in a statement.
The lack of blue clusters suggests that NGC 1277 never grew by merging with surrounding galaxies. The astronomers explain that this is because NGC 1277 is moving so fast through its region of the universe (2 million miles per hour) that it cannot merge with smaller satellite galaxies, starving itself of the outside material required to power new star formation.
In addition, the prevalence of red globular clusters indicates that NGC 1277 stopped generating stars long ago. The researchers say gas in the center of the galaxy is so hot that it cannot cool and condense to form new stars.
"I didn't believe the ancient galaxy hypothesis initially, but finally I was surprised because it's not that common to find what you predict in astronomy," Beasley added. "Typically, the universe always comes up with more surprises than you can think about."
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