Astronomers spy on cosmic dust, with a twist, that is barely older than the universe.

The universe is a dusty place. Cosmic particles can range from the size of a single large molecule to slightly larger than an Earth grain of sand, and can accumulate in billowing clouds light-years across. The general scientific understanding was that dust gradually accumulates, produced by stars and supernovae over hundreds of millions of years. Dust is usually a fixture of mature galaxies, or so astronomers thought.

But in a new article published Wednesday in the magazine Nature, astronomers found a specific type of high-carbon cosmic dust in distant young galaxies just 800 million years after the Big Bang. That accumulation occurred much earlier than current theories of dust formation suggest. It’s a finding that could change how astronomers understand star creation and galaxy evolution in the early universe, and ultimately how that young universe became the cosmos we know today.

For a long time, astronomers treated cosmic matter the way we might see a dust bunny under a sofa: as a nuisance. Scientists tried to look beyond the vast clouds of cosmic dust, treated more as obstacles than study subjects in their own right. “The way most astronomers interact with it is that [dust] it actually absorbs a lot of the light that we’re trying to observe,” says the study’s lead author, Joris Witstok, a postdoctoral researcher at the Kavli Institute for Cosmology in Cambridge, UK.

But that has changed in recent years, thanks to observatories like NASA’s James Webb Space Telescope, which uses infrared light to see through clouds. Scientists have also come to appreciate the dust itself, realizing that these tiny particles of carbon, silicon, and other matter are responsible for large-scale processes in the universe, such as the formation of new stars.

“For example, in the Milky Way, we have these sites where new stars are forming, and they are very dusty,” says Witstok. “There are big clouds of gas and dust, and the dust really helps allow the gas to cool and contract and therefore form new stars.”

[Related: 5,000 tons of ancient ‘extraterrestrial dust’ fall on Earth each year]

It’s not that the early universe was dustless. Previous studies had found large amounts of dust in galaxies in the very early universe, according to Witstok. Astronomers are interested in this early dust because it represents when stars began to produce some of the first elements heavier than hydrogen.

“The first stars that started converting hydrogen into helium, which was all there was at the beginning, into heavier elements like carbon and oxygen,” says Witstok.

Large primordial stars may have ejected large amounts of dust, made of these heavier elements, towards the end of their life cycles, or during supernova explosions when they died.

But previous studies had been unable to detect carbonaceous dust, meaning it is rich in carbon, at such early times.

“What’s really a new discovery here is that we can identify the type of dust grains we’re seeing,” says Witstok. “What we can actually say is that there is something specifically producing these grains of carbon dust on a very short time scale. And that’s where the surprise lies.”

Spectrographic observations of the closest dust to Earth, within the Milky Way, made this discovery possible. Spectroscopy divides light into a spectrum and looks for telltale signs of absorbed light at certain wavelengths associated with different elements and compounds, sort of like reading a single rainbow.

The carbonaceous dust produces a spectroscopic “bump” at a wavelength of 217.5 nanometers, a wavelength that places it in the ultraviolet portion of the spectrum. At least, that’s the wavelength of the light when it left its home galaxy billions of years ago.

“Since it’s been traveling for about 13 billion years, as the universe expands, light actually gets stretched with that expansion,” says Witstok, a phenomenon known as redshift. The light that was ultraviolet is stretched further so that the wavelength (about 1.5 to 2 micrometers) is now in the infrared, the JWST part of the spectrum is set to measure.

“That’s exactly why we couldn’t do this before,” says Witstok. “Because with JWST, now for the first time we can look at and make these very precise measurements in the infrared.”

[Related: Physicists figured out a recipe to make titanium stardust on Earth]

Now that the researchers have measured this carbonaceous dust at an earlier time in the universe than expected, they are left trying to figure out what process might be producing it. There are two theories, Witstok says, although neither is perfect.

The first is that supernovae in early galaxies create the dust, and dying stars eject the material before their final death throes. But the problem there, he says, is that the violent forces unleashed by supernovae could also destroy much of that dust.

Another source of dust could be Wolf-Rayet stars, massive, hot, and fast-burning stars that can expel much of their mass into space in less than a million years. “But then again, it’s the question of how much can they actually produce.” Wistock says. “Is it enough to explain what we’re seeing in the early universe?”

Witstok and his colleagues hope to answer those questions with computer simulations. Theorists may try to modify models of supernovae and Wolf-Rayet stars to try to find the conditions that produce the carbonaceous dust seen in the JWST observations.

And other observations of the earliest galaxies may also yield answers, he says. “We could start to look at what could be indications of an unusual number of Wolf-Rayet stars within those galaxies, for example.”

Whatever is driving the creation of carbonaceous dust in the early universe may hold clues to understanding how galaxies evolved in the most recent universe and how stars and planets form as well. “Dust is a really key component of how galaxies evolve,” says Witstok. “The fact that we are now starting to see more and more evidence of its very early formation tells us that perhaps this evolution is happening faster than we previously thought. That then has a knock-on effect, going forward, as to how we got to the present.”

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