At the universe’s infancy, two dwarf-galaxies formed and were speeding towards each other. Thus, confronting one another and assembling into a large galaxy.

Based on current theories, in the universe’s infancy galaxies were tiny. So, they needed to merge with each other to form larger ones that we see today.

However, using the world’s largest radio telescope – the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile – researchers unveiled something that made them re-think the leading theory of how galaxies form.

They found evidence of massive galaxies forming in a sea of dark matter much quicker than we thought.

So, astronomers were surprised to find that these enormous galaxies existed when the universe was only 780 million years old. Currently, the universe is 13.8 billion years old, meaning that those galaxies existed when the universe was 5% of its current age.

Astronomers call these two galaxies collectively as SPT0311-58.

Knowing that it takes time for light to travel, astronomers were basically looking back in time. Looking at the dawn of the universe.

“With these exquisite ALMA observations, astronomers are seeing the most massive galaxy known in the first billion years of the universe in the process of assembling itself,” Dan Marrone, an associate professor of astronomy at the University of Arizona in Tucson and lead author of the new papersaid in a statement.

ALMA shot of galaxies

The image is showing ALMA data of the two galaxies of SPT0311-58 in red. These galaxies are shown over a background image from the Hubble Space Telescope. Credit: Marrone, et al./B. Saxton/AUI/NSF/ALMA/ESO/NAOJ/NRAO/NASA/ESA/Hubble

Epoch of Reionization

This assembling occurred in an era of the universe known as the Epoch of Reionization. This is a time when an obscuring fog of cold hydrogen gas fills the intergalactic space. At this time, first galaxies came together and lit up the universe. Thus, the energy from their starlight began to ionize the hydrogen gas, making our universe more transparent, just like it is today.

The team of astronomers, using advanced computer models, was able to see that the larger of the two galaxies is forming stars at a rate of 2,900 solar masses per year.

The Milky Way’s mass is equal to some 480 billion suns, while SPT0311-58 has about 440 billion solar masses. They also observed the elusive and mysterious dark matter halo surrounding both galaxies.

Though astronomers can’t see the dark matter halo, through gravitational interactions with galaxies, they can infer its presence.

However the team wants to continue the hunt for other galaxies.

“Our hope is to find more objects like this, possibly even more distant ones, to better understand this population of extreme dusty galaxies and especially their relation to the bulk population of galaxies at this epoch,” said Joaquin Vieira of the University of Illinois at Urbana-Champaign in a press release.

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Thumbnail image: Artist’s impression of a pair of galaxies from the very early universe. Credit: NRAO/AUI/NSF/D Berry