Pollution alert in the early universe

Pollution alert in the early universe

Read time: 3 minutes

We all know about environmental pollution. The air is polluted by cars, airplanes and factories. The
oceans are polluted with plastic. Humans produce a lot of filth that spreads throughout our world,
slowly but surely.
Now, astronomers have discovered the first environmental pollution in the universe. It’s not
produced by humans, but by stars. But just like human filth, it is spreading away from its source.
The very first stars in the universe were born from huge clouds of gas. Right after the big bang, the
only gases available were hydrogen and helium – other elements did not yet exist. But in the hot
interiors of stars, atoms of hydrogen and helium fused together into heavier elements, like carbon
and oxygen. When stars grow old, they can blow some of these newly formed elements into space,
just like a factory releases dirt into the atmosphere.
Little surprise, then, that distant galaxies contain carbon atoms, floating around in the space
between the stars. But now, ALMA has revealed that this ‘cosmic pollution’ extends well beyond the
galaxies’ edge. It’s as if the pollution of factories in the United States turns out to extend all the way
across the Atlantic and Pacific Oceans.
By studying existing ALMA observations of remote galaxies, the astronomers discovered that these
galaxies are surrounded by huge clouds of carbon gas. Apparently, the ‘pollution’ from stars in the
galaxy is somehow blown out into space. How? Perhaps by supernova explosions, or maybe by
supermassive black holes in the galaxy’s core. But no one knows for sure.
The light from distant galaxies take billions of years to reach our telescopes here on Earth. Therefore,
we see these galaxies as they were long ago, just one billion years after the big bang or so. No one
had expected that ‘cosmic pollution’ would already be so severe back then. In fact, scientists have no
satisfying explanation for the huge carbon clouds. Hopefully, the discovery will help astronomers to
better understand the very first stages of the evolution of galaxies.
Incidentally, we shouldn’t worry too much about this massive environmental pollution in the early
universe. After all, life is based on carbon chemistry. Without the large-scale release and distribution
of carbon atoms in the universe, we wouldn’t be here!


The discovery of huge carbon clouds surrounding remote galaxies was not the result of new ALMA
observations. Instead, the astronomers combined existing observations of 18 distant galaxies that
were available in the ALMA archive. By adding many earlier measurements together, they achieved
enough sensitivity to detect the submillimeter radiation of ionized carbon – carbon atoms that have
lost two electrons. In most cases, they found that the galaxies are enveloped in huge clouds of
carbon gas. The clouds extend to distances of some 30,000 light-years – about five times the size of
the galaxies themselves.


The discovery was made by an international team of astronomers, led by Seiji Fujimoto of the
University of Tokyo in Japan. Seiji worked together with colleagues from Japan, the United Kingdom,
Italy, Germany, and the United States. They published their results in a major professional astronomy
magazine called The Astrophysical Journal.