Galaxy Trio Discovered Caught Merging Near 'Cosmic Dawn'
Researchers have identified a trio of galaxies embedded in a dust cloud located nearly 13 billion light years from Earth, placing them back in time to the Universe's beginnings.
First detected in 2009, the object appeared simply as a giant bubble of hot, ionized gas, with later observations suggesting it might be a single galaxy. Not until researchers turned NASA's Hubble Space Telescope and the powerful Atacama Large Millimeter/submillimeter Array (ALMA) telescope on it did they recognize it for what it was.
"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," Richard Ellis, an astronomer professor at the California Institute of Technology and member of the research team, said in a statement.
Even more intriguing is that the three appear poised to merge, Ellis explains, noting that if they do, they would eventually evolve into an object resembling our own galaxy.
Most regions of such intense star formation are stuffed full of heavy elements, including carbon, silicon and oxygen -- all of which are born in the nuclear furnaces of massive stars like those being assembled in the three galaxies. When those stars explode as supernovas, they seed the universe with these heavy elements. However, researchers have been entirely unsuccessful in detecting any of these basic ingredients.
"Surprisingly, observations with ALMA revealed a complete absence of the signal from carbon, which is rapidly synthesized in young stars. Given the sensitivity of ALMA, this is truly remarkable," said Masami Ouchi, an associate professor at the University of Tokyo. "Exactly how this intense activity can be reconciled with the primitive chemical composition of Himiko is quite puzzling."
One possibility is that much of the gas in and around the galaxies is comprised of helium and hydrogen, both of which were created in the Big Bang.
"Astronomers are usually excited when a signal from an object is detected," Ellis said. "But, in this case, it's the absence of a signal from heavy elements that is the most exciting result!"