Our Galaxy Is Really Greasy and Smells Like Moth Balls

A new study estimates that a quarter to half the carbon in interstellar space is in the form of greasy aliphatic carbon

Space Grease
D. Young, The Galactic Center

One of the coolest parts of the Star Wars franchise is when spaceship pilots engage the hyperdrive, which allows them to jump around the galaxy faster than the speed of light. But Hannah Devlin at The Guardian reports that a new study suggests those pilots would likely need to turn on the windshield wipers — and take their ship to the nearest WookieWash after landing. That’s because those vast empty reaches of space between stars are filled with interstellar dust. That dust is actually a mix of grease, soot and silicate sand. And there's a lot more grease than we thought.

Researchers already understood that space contains greasy soot, but for this new study they wanted to understand just how much of the stuff fills the cosmos. Carbon stars, such as red giants, create their namesake element by fusing helium atoms in their cores, eventually pumping the carbon out into space. Over time, that carbon coalesces into new stars, planets and creates the building blocks of life.

Researchers believe that about half of the carbon remains in its pure form while the rest of it binds with hydrogen, creating either greasy aliphatic carbon or gaseous naphthalene, the stuff used in mothballs. Aliphatic carbon is a term for a class of molecules where carbon atoms are arranged in chains, rather than in a ring. On earth, propane and butane are examples of aliphatic carbon compounds. In space, the compounds are just called grease.

For the new study, the researchers wanted to get an estimate for how much aliphatic carbon is in the Milky Way. According to a press release describing the research, the team mimicked the formation of aliphatic carbon in interstellar space in the lab, expanding a carbon-containing plasma inside a vacuum tube at low temperature. They then used spectroscopy and magnetic resonance to determine how much infrared light aliphatic carbon absorbs. With that data they were able to calculate just how much space grease is out there. The study appears in the journal Monthly Notices of the Royal Astronomical Society.

The number is staggering. The greasy carbon makes up between a quarter and half of all the carbon in our galaxy. That adds up to 10 billion trillion trillion tons of grease, or enough to fill 40 trillion trillion trillion packs of butter, co-author Tim Schmidt of the University of New South Wales says in the release. But it’s very un-butter-like, he emphasizes. “This space grease is not the kind of thing you’d want to spread on a slice of toast! It’s dirty, likely toxic and only forms in the environment of interstellar space (and our laboratory),” he says. “It’s also intriguing that organic material of this kind – material that gets incorporated into planetary systems – is so abundant.”

Astronomer Helen Fraser of Open University, not involved in the study, tells Devlin the study suggests there’s more greasy carbon in the cosmos than previously believed, which could change how we understand planet formation. “The consequence could be important in how such dust grains stick and form planets, or even ‘seed’ planetary surfaces with the ingredients for the origins of life,” she says.

So what does this all mean for the Millennium Falcon and its crew? And why aren’t our satellites and space probes coated in grease? Luckily for us, solar wind within our solar system sweeps away all the grease in our immediate neighborhood. But any craft traveling into interstellar space better bring a little degreaser, though Schmidt tells Thomas Oriti at the Australian Broadcasting Corporation that the gloop would not be his primary concern. “There will be material that will coat space craft, but I would worry more about the little rocks and many asteroids that are around planetary systems,” he says. “Once you’re into deep space, there is really only the very small particles.”

Brad Tucker, an astrophysicist from Australian National University, not affiliated with the study, agrees that the grease is not too gunky. “It’s not like we’ve just had a nice BBQ and dumped all the sausage fat all over it,” he says. “It’s not that dense." But the goop could still pose problems, he adds. "[I]f you're travelling through it, you're going to be bombarded with all of these compounds or all these chemicals.”

Schmidt tells Jessie Yeung at CNN that the next step will be to try and find a way to quantify the amount of naphthalene carbon there is among the stars, to finally nail down the ratio of grease to mothballs to pure carbon. “Aliphatic material is kind of boring,” he says. “It’s grease. The aromatic carbon actually has a relationship with graphene (a semi-metal), which makes it quite interesting. So researching in that direction is going to be pretty interesting.”

Especially if they find out all that naphthalene is there to keep giant space moths out of our galaxy.

Get the latest stories in your inbox every weekday.