Buckyballs in space

Carbon is an important little atom. It is not for nothing that we are referred to as “carbon-based”, when combined with hydrogen, the resulting complex hydrocarbon molecules are the basis of what is known as organic chemistry, providing plastics, oils and gases on which our civilisation is based. But in its purest forms, carbon is also quite useful – diamond, the crystal form of carbon, is a strong, nice looking gemstone; graphite, where layers of joined carbon atoms sit on one another, forms the basis of pencils, where the layers rub apart to leave a deposit, and carbon fibre materials make use of the strength of the layers to produce sturdy, heat resistant, lightweight materials. In astronomy, both of these forms of carbon are seen to exist. As white dwarf stars cool, they rearrange themselves until the carbon in them starts to become diamond. As for graphite, recent examinations of Apollo Moon-rocks have seen ‘grey whisker’, essentially carbon nanotubes or wrapped up graphite layers, deposited in the samples. But there is another form of carbon.

Buckminsterfullerenes, or Buckyballs, are molecules composed of sixty carbon atoms arranged in a geodesic ball, resembling the work of architect Richard Buckminster Fuller, after whom they are named. Buckyballs were first anticipated in 1970, but not observed in the lab until 1985. Now they have been spotted in space alongside C70, the 70 carbon atom equivalent, which now holds the record as the largest molecule spotted in the cold, dark of space.

It was known from laboratory experiments that buckyballs formed in the atmospheres of stars – it was one such experiment that led to the discovery of the things – but until now, they had never been seen. The Spitzer infrared space telescope, now on a zombie mission, having outlived the coolant that allowed its original cold mission to go ahead, scanned the remains of a star in the form of planetary nebula Tc1. It appears that the star gasped out its carbon rich layers, which are now cooling around a white dwarf stellar remnant. As that slowly turns to diamond, the buckyballs and possibly grey whiskers of graphite lie in orbit or escaping the stellar death throes. The carbon molecules were radiating energy at around room temperature, allowing them to be picked up by Spitzer, but it is estimated in one hundred years or so, they will be too cool to detect.

The very stable molecules are likely to be floating around for some time, however they will become too cool to see directly. Their indirect effects will include scattering of starlight in a characteristic way and interstellar chemistry, both factors in common with the grey whiskers and things that astronomers making detections through a very thin haze of these things need to account for.

The story has been reported here on the BBC, here in Astronomy Now and here in a NASA press release, which includes a video interview.


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