A galaxy takes the place of many 9.2 billion light-years from Earth

A single galaxy has characteristics that only scientists saw possible in a cluster of them, defying all theories about it.


A lonely, distant galaxy appears to have swept away and assimilated all of its former companion galaxies , NASA ‘s Chandra X-ray Observatory and the Gemini International Observatory reveal.

The unexpectedly lonely galaxy is located about 9.2 billion light-years from Earth and contains a quasar, a supermassive black hole that pulls in gas at the center of the galaxy and drives powerful jets of matter seen in radio waves. The environment of this galaxy , known as 3C 297 , appears to have the key features of a cluster of galaxies , huge structures that typically contain hundreds or even thousands of galaxies. However, 3C 297 stands alone.

“It seems that we have a galaxy cluster that is missing almost all of its galaxies ,” says Valentina Missaglia of the University of Turin, Italy, who led the study. “We expected to see at least a dozen galaxies the size of the Milky Way, and yet we only see one.”

one instead of many

Missaglia and his colleagues observe two key features of a galaxy cluster in the Chandra X-ray data . First, they reveal that the lone galaxy is surrounded by vast amounts of gas with temperatures in the tens of millions of degrees, something normally seen in galaxy clusters .

Second, the jet from the supermassive black hole has created an intense X-ray source some 140,000 light-years away, implying that it has penetrated the gas surrounding the galaxy . A third feature of the galaxy clusters in 3C 297 , previously reported in data from the Karl G. Jansky Very Large Array, is that one of the radio jets is bent, showing that it has interacted with its surroundings. .

Despite having these important features of a galaxy cluster , Missaglia’s team’s data from the Gemini Observatory in Hawaii revealed that none of the 19 galaxies that appear near 3C 297 in an optical image of Gemini, and that have precise measurements away, they are really at the same distance as the lone galaxy .

“The question is, what happened to all these galaxies ?” said co-author Juan Madrid, of the University of Texas, Rio Grande Valley. “We think that the gravitational pull of the single large galaxy combined with the interactions between the galaxies was too strong, and they merged with the large galaxy .” Apparently, for these galaxies resistance was futile.”

Researchers believe that 3C 297 is no longer a galaxy cluster , but a “fossil clump”. It is the final stage of a galaxy that is crawling and merging with other galaxies . Although many other fossil groups have already been detected, this one lies 9.2 billion light-years away. (Previous records for fossil groups were at distances of 4.9 and 7.9 billion light-years.)

“It can be challenging to explain how the universe could create this system just 4.6 billion years after the Big Bang,” said co-author Mischa Schirmer, of the Max Planck Institute for Astronomy. “This doesn’t break our ideas of cosmology, but it does start to push the limits of how fast both galaxies and clusters of galaxies must have formed .”

The authors cannot rule out the presence of dwarf galaxies around 3C 297 , but their presence would still not explain the absence of larger galaxies like the Milky Way. Nearby examples are M87 in the Virgo Cluster, which has had large galactic companions for billions of years. However, 3C 297 will spend billions of years essentially alone.