The galaxy is rich in grease-like molecules, say scientists who have estimated the amount of ‘space grease’ found in the Milky Way. Organic matter of different kinds contains carbon, an element considered essential for life. There is though real uncertainty over its abundance and only half the carbon expected is found between the stars in its pure form.
The rest is chemically bound in two main forms, grease-like (aliphatic) and mothball-like (aromatic). The researchers from University of New South Wales (UNSW) in Australia used a laboratory to create a material with the same properties as interstellar dust. They mimicked the process by which organic molecules are synthesized in the outflows of carbon stars, by expanding a carbon-containing plasma into a vacuum at low temperature. The material was collected and then analyzed by a combination of techniques. Using magnetic resonance and spectroscopy (splitting light into its constituent wavelengths) they were able to determine how strongly the material absorbed light with a certain infrared wavelength, a marker for aliphatic carbon.
“Combining our lab results with observations from astronomical observatories allows us to measure the amount of aliphatic carbon between us and the stars,” said Tim Schmidt, from UNSW. The study, published in the journal Monthly Notices of the Royal Astronomical Society, found that there are about 100 greasy carbon atoms for every million hydrogen atoms, accounting for between a quarter and a half of the available carbon. In the Milky Way galaxy, this amounts to about 10 billion trillion trillion tonnes of greasy matter or enough for 40 trillion trillion trillion packs of butter.
“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),” said Schmidt. “It’s also intriguing that organic material of this kind – material that gets incorporated into planetary systems – is so abundant,” he said.
The team now wants to determine the abundance of the mothball-like carbon, which will involve yet more challenging work in the laboratory. By firmly establishing the amount of each type of carbon in the dust, they will know precisely how much of this element is available to create life.