When a comet approaches the sun, its head turns green. Scientists now think they know why the tail is not coloured.
the chassis with a green head only; It would be a strange sight. However, it is a daily image of comets ejected from the Kuiper Belt and the Oort Cloud. During their journey towards the sun, their heads turn green. This color gets brighter as they approach our parent star. But this green glow disappears before it reaches the comet’s tail.
Scientists have been asking the question for a century: Why does only the head of a comet turn green? In the 1930s, German physicist Gerhard Herzberg proposed a possible explanation. When UV light from the Sun interacts with the organic matter in a comet’s head, diatomic carbon (C2) formed. This gives a green glow. But once this substance is formed, sunlight quickly breaks it down again, so that the color never reaches the tail.
However, because diatomic carbon is very unstable, it was very difficult to test Herzberg’s theory. But scientists at the University of New South Wales (UNSW Sydney) have now succeeded. and out their studies It turns out that the German physicist was right.
To do this, the scientists pulled out a vacuum chamber, lots of lasers, and a speedometer. “First of all, we had to make diatomic carbon. You can’t just buy this at the store,” says chemist Timothy Schmidt. “We created this by pointing an ultraviolet laser over perchloroethylene (C.2Cl4) – this released chlorine (Cl) atoms. ” C2, diatomic carbon, remained.
These particles blasted the scientists in the form of a gas jet through a two-meter-tall vacuum chamber. Then they called it two ultraviolet lasers. Indeed, the diatomic carbon, which colors the comet green, was quickly broken down into two separate carbon atoms.
“This work shows very well that very precise laboratory work can simulate chemistry because it occurs in the (almost) vacuum of space,” says astronomer Michael Hogerheide of the University of Amsterdam. “These kinds of experiments are important because they look at properties of molecules that we will never encounter on Earth.”
Hogerheide continues: “A lot of theoretical calculations can indeed be expected (as Professor Herzberg did long ago), but confirmation in the lab is the ultimate proof.” Very beautiful work.
Photo: JOHN VERMETTE / WIKIMEDIA COMMONS