Three Ancient Galaxies Spotted Merging


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Astronomers this week revealed that they have spotted three ancient galaxies that appear to be merging. The observations, which were made using both the Hubble Space Telescope and the Atacama Large Millimeter/submillimeter Array (ALMA) are recorded in a paper to be published in The Astrophysical Journal.

The three galaxies are located inside a large gas cloud that is located almost 13 billion light-years from our solar system. This means the galaxies are seen as they were less than one billion years after the big bang. Astronomers believe that the galaxies might have eventually merged, forming a larger galaxy similar to the ones we are more familiar with today.

“This exceedingly rare triple system, seen when the Universe was only 800 million years old, provides important insights into the earliest stages of galaxy formation during a period known as ‘Cosmic Dawn,’ when the Universe was first bathed in starlight,” said Richard Ellis, a member of the research team and an astronomer at the California Institute of Technology. “Even more interesting, these galaxies appear poised to merge into a single massive galaxy, which could eventually evolve into something akin to the Milky Way.”

The gas cloud, which researchers have dubbed "Himiko" was first spotted in 2009 and was seen as a single gas cloud. However, the size of the cloud is, according to the National Radio Astronomy Observatory, almost ten times larger than the nebulous galaxies that are found that early in the universe. This led to the new observations, which revealed that three distinct sources of light within the larger cloud.

What astronomers did not find, however, could end up being their most interesting observation. The team did not detect any carbon in Himiko, which is one of the first elements created by young stars.

“When this dust is heated by ultraviolet radiation from massive newborn stars, the dust then re-radiates at radio wavelengths,” said Kotaro Kohno, a member of the research team and an astronomer at the University of Tokyo. “Such radiation is not detected in Himiko.”

Kohno and his colleagues currently believe that this could signal that Himiko is, in fact, a primordial galaxy made up mostly of hydrogen and helium gas. This would make it one of the first primordial galaxies to be caught during its early formation.

(Image courtesy NASA/Hubble; NAOJ/Subaru)