This Dust-Filled Galaxy Formed Less Than A Billion Years After The Big Bang

Artist’s depiction of MAMBO-9, a dust-filled, star-forming galaxy that formed a mere 970 million years after the Big Bang. (Image: NRAO/AUI/NSF, B. Saxton)

Astronomers have spotted an unusually distant star-forming galaxy, the light of which took a whopping 13 billion years to reach Earth. Perhaps most incredibly, however, the galaxy was observed directly, without the help of a celestial phenomenon known as gravitational lensing.

This galaxy is called MAMBO-9, and it was actually detected 10 years ago with the Max-Planck Millimetre Bolometer (MAMBO) instrument attached to the IRAM 30-metre telescope in Spain. At the time, astronomers were unable to discern the galaxy’s distance from Earth owing to its incredibly low luminosity. Astronomers knew it was far, they just didn’t know how far.

But now they do, thanks to the sensitivity offered by the Atacama Large Millimetre/submillimeter Array (ALMA), which is located in the Chilean Andes. New research published in The Astrophysical Journal places MAMBO-9 at a distance of 13 billion light-years from Earth—a remarkable observation, given that the universe itself is 13.8 billion years old. MAMBO-9 formed a mere 970 million years after the Big Bang. This ancient galaxy, therefore, is like a portal back in time, allowing astronomers to catch a literal glimpse of what the universe looked like during this very early stage in its formation.

An ALMA radio image of the dusty star-forming galaxy, which consists of two parts and is in the process of merging. (Image: ALMA (ESO/NAOJ/NRAO), C.M. Casey et al.; NRAO/AUI/NSF, B. Saxton)

Older galaxies have been spotted before, including galaxy SPT0311-58, which formed a mere 780 million years after the Big Bang. What’s particularly special about MAMBO-9, however, is that it’s the most distant and subsequently the oldest dusty galaxy to be directly observed by telescopes, without the benefit of gravitational lensing—a magnification effect in which the gravity of a foreground galaxy warps the light from one behind it.

“We found the galaxy in a new ALMA survey specifically designed to identify dusty star-forming galaxies in the early universe,” said Caitlin Casey, an astronomer from the University of Texas at Austin and the lead author of the new study, in a press release. “And what is special about this observation, is that this is the most distant dusty galaxy we have ever seen in an unobstructed way.”

By “dusty galaxy,” Casey is referring to massive dust-filled, star-forming galaxies. These types of galaxies can spawn stars amounting to thousands of solar masses per year, in which one solar mass equals the weight of our Sun. By comparison, the Milky Way produces around three solar masses’ worth of stars each year. Most of these gigantic stellar factories formed long after the universe reached a certain level of maturity, but some have been observed at less than 1 billion years after the Big Bang, including the aforementioned SPT0311-58. Given their surprisingly early appearance, dusty galaxies likely played an important role in the development of the early universe.

Casey and her colleagues were also able to measure the total mass of gas and dust packed into MAMBO-9. This primordial galaxy contains gas and dust amounting to 10 times the mass of all the stars in the Milky Way—it’s huge. This is a really neat observation, because it means MAMBO-9, some 13 billion years ago from our perspective, had yet to produce the vast majority of stars it was destined to create (it very likely managed to produce those stars, but we’ll never have the opportunity to see them unless we manage to observe MAMBO-9 for the next 4 billion to 6 billion years or more).

The astronomers detected two discernible sections of the galaxy, a big section and a small section, which are in the process of merging.

In an email to Gizmodo, astronomer Robert Minchin, a senior scientist from the Stratospheric Observatory For Infrared Astronomy (SOFIA) at NASA Ames Research Centre, said the new paper “certainly looks interesting.”

“Unlike with gravitationally lensed galaxies, we have an undistorted view of MAMBO-9,” he said. “ALMA has been able to resolve the source into a galaxy pair that is quite possibly in the process of merging, which is likely to have triggered the starbursts in the source—we are basically seeing a galaxy caught in the process of formation,” said Minchin, who wasn’t involved with the new study.

As noted, MAMBO-9 was catalogued a decade ago, but only now have astronomers been able to determine its distance.

“There are many more sources already in catalogues that might be equally interesting but which haven’t yet been spectroscopically confirmed,” said Minchin. “Unfortunately such confirmation requires lots of expensive telescope time, which is in high demand.”

Looking ahead, Casey and her colleagues are hoping to use ALMA to find similarly old and distant galaxies to get a sense of how common they were back then and to figure out how they managed to acquire so much gas and dust so soon after the Big Bang.