Astronomers using the ALMA telescope have spotted two massive, star-filled galaxies wrapped in a halo of dark matter. The galaxies, which are bound to merge into one, are seen as they appeared when the universe, which is now about 13.7 billion years old, was not even one billion years old.

In a paper published in the journal Nature, astronomers have painted a new picture of the early universe. According to their observations, a pair of massive galaxies existed around 780 million years after the universe formed in the Big Bang. This contradicts the current theory which suggests early universe galaxies were similar to small, low-mass dwarf galaxies we see today, while the larger ones came into existence a few billion years later.

Initially, the galactic pair was first seen as a single object, dubbed SPT0311-58, from South Pole Telescope, but, subsequent observations from ALMA revealed that these are two galaxies, separated by several thousand light-years.

As a report in Seeker notes, the light from these galaxies took around 13 billion years to reach Earth, so they appear as they did when the universe was young.

Eventually, these galaxies will merge to form one of the largest galaxies known in the first billion years of the universe.

According to the observations, both galaxies are likely going through a burst of star formation. The larger of the two carries about 273 billion times the mass of our sun in dust and gas, while smaller one already has about 35 billion solar masses of stars.

Galactic pair
A composite image showing the dusty glow of the two galaxies of SPT0311-58. ALMA ESO/NAOJ/NRAO), Marrone, et al.; B. Saxton (NRAO/AUI/NSF; NASA/ESA Hubble

But that's not the only thing that has been discovered. Researchers also found these galaxies to be surrounded by a halo of dark matter, something that suggests dark matter also had a role to play in the process of assembling the large cosmic structures of the universe.

The ocean of dark matter surrounding the galaxies wasn't visible, but the researchers inferred its presence through gravitational interaction with the galaxies. Further calculations revealed it is one of the most massive from that time, measuring several trillion times more than the sun.

Moving ahead, researchers hope to find more early-universe objects like these. "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 (epoch of reionisation -- the period when first galaxies came together).