Astronomers uncover ‘invisible’ massive ancient galaxies
Although once invisible to us in the vast reaches of the universe, 39 massive ancient galaxies have been discovered by astronomers using multiple space and ground-based observatories. This is the first discovery of its kind, the researchers said.
“This is the first time that such a large population of massive galaxies was confirmed during the first 2 billion years of the 13.7-billion-year life of the universe. These were previously invisible to us,” said Tao Wang, study author and researcher at the University of Tokyo, French Alternative Energies and Atomic Energy Commission, and the National Astronomical Observatory of Japan. “This finding contravenes current models for that period of cosmic evolution and will help to add some details, which have been missing until now.”
The study published Wednesday in the journal Nature.
The new prevalence of these galaxies, which are connected with supermassive black holes and dark matter, contradicts the current known models of the universe.
Given their age and distance, the massive galaxies were hidden from our view because their light is weak and stretched. The universe is also expanding, which makes the distance greater. Over that distance, visible light becomes infrared, according to the study.
“The light from these galaxies is very faint with long wavelengths invisible to our eyes and undetectable by Hubble,” said Kotaro Kohno, study author and professor at the University of Tokyo.
“So we turned to the Atacama Large Millimeter/submillimeter Array (ALMA), which is ideal for viewing these kinds of things. I have a long history with that facility and so knew it would deliver good results.” The Atacama complex is located in Chile.
Galaxies also have a bit of a dust problem, which cloaks the largest galaxies even more than smaller ones.
Studying these galaxies can also reveal more information about supermassive black holes.
“The more massive a galaxy, the more massive the supermassive black hole at its heart. So the study of these galaxies and their evolution will tell us more about the evolution of supermassive black holes, too,” said Kohno.
“Massive galaxies are also intimately connected with the distribution of invisible dark matter. This plays a role in shaping the structure and distribution of galaxies. Theoretical researchers will need to update their theories now.”
Looking up at the night sky, our galaxy the Milky Way appears a bit like spilled milk. But if we lived in one of these massive ancient galaxies, the view would be different.
“For one thing, the night sky would appear far more majestic. The greater density of stars means there would be many more stars close by appearing larger and brighter,” explained Wang. “But conversely, the large amount of dust means farther-away stars would be far less visible, so the background to these bright close stars might be a vast dark void.”
Future space-based telescopes could shed more light on the composition, number of stars and the chemicals in these galaxies.
“Previous studies have found extremely active star-forming galaxies in the early Universe, but their population is quite limited,” Wang said. “Star formation in the dark galaxies we identified is less intense, but they are 100 times more abundant than the extreme starbursts. It is important to study such a major component of the history of the Universe to comprehend galaxy formation.”