Astronomers have witnessed a star, known as SDSSJ1240+6710, being thrown across the galaxy at almost 1 million kilometres per hour. This type of event has not previously been known and is believed to be the result of a partial supernova.
In most cases, supernovae occur when a star dies. At the end of their lives, they implode in on themselves and then erupt a huge amount of energy into space, this is in fact is how all elements in the universe other than hydrogen and helium are created. In this case however, it appears that the star did not die but was itself shot out of its normal position and sent hurtling through space.
Usually, stars are made up almost entirely of hydrogen and helium, this star however, based on current evidence, is also comprised of silicon, oxygen, neon and magnesium. It is known that the star underwent at least a partial supernova as these elements would not otherwise exist. It is also thought that the star was part of a binary pair, which is when two stars circle each other, and that the other star must have been sent hurtling in the opposite direction. It was this fairly unusual relationship that may have resulted in the star's unique behaviour.
Professor Boris Gänsicke, of the University of Warwick, who led the investigation, spoke of just how unusual the star is. He said:
"This star is unique because it has all the key features of a white dwarf but it has this very high velocity and unusual abundances that make no sense when combined with its low mass. It has a chemical composition which is the fingerprint of nuclear burning, a low mass and a very high velocity; all of these facts imply that it must have come from some kind of close binary system and it must have undergone thermonuclear ignition. It would have been a type of supernova, but of a kind that that we haven't seen before."
He went on to explain how the nuclear reaction process in stars normally takes place:
"The process developing during a thermonuclear supernova is very similar to what we try to achieve on Earth in our future power plants: nuclear fusion of lighter elements into heavier ones, which releases vast amounts of energy. In a fusion reactor, we use the lightest element, hydrogen (more specifically, different flavours, or isotopes of it). In a thermonuclear supernova, the density and temperature in the star becomes so high that fusion of heavier elements ignites, starting with carbon and oxygen as 'fuel', and fusing heavier and heavier elements."
Until recently, it had been believed that supernovas only occur in one generic manner, but there is a growing body of evidence, of which this discovery is one, that they can take on many different unique forms and behaviours.
This is one more small step towards understanding the wonders of the universe.
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