Nuclear explosion sends the star speeding across the galaxy


Partial supernovaImage copyright
University of Warwick / Mark Garlick

A star has been sent at full speed through the galaxy after suffering a partial supernova, astronomers say.

A supernova is a powerful explosion that occurs when some stars reach the end of their lives; in this case, the explosion was not enough to destroy it.

Instead, it sent the star speeding through space at 900,000 km / h.

Astronomers think that the object, known as a white dwarf, originally surrounded another star, which would have been sent flying in the opposite direction.

When two stars orbit each other in this way, they are described as “binary”. However, only one of the stars has been detected by astronomers.

The object, known as SDSS J1240 + 6710, was previously found to have an unusual atmospheric composition.

Discovered in 2015, it appeared to contain no hydrogen or helium (usually found), and appears to be composed of rather than an unusual mixture of oxygen, neon, magnesium, and silicon.

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Now, using the Hubble Space Telescope, an international team has also identified carbon, sodium and aluminum in the star’s atmosphere, all of which occurs in the first thermonuclear reactions of a supernova.

But there is also a clear absence of what is known as the “iron group” of elements, iron, nickel, chromium, and manganese.

These heavier elements are normally cooked from the lighter ones and constitute the defining characteristics of thermonuclear supernovae.

The lack of elements of the iron group in SDSSJ1240 + 6710 suggests that the star only experienced a partial supernova before nuclear burning was extinguished.

Lead author Professor Boris Gänsicke from the Physics Department at the University of Warwick, UK said: “This star is unique because it has all the key characteristics of a white dwarf, but it has this very high speed and unusual abundances that They don’t make sense when combined with their low mass.

“It has a chemical composition that is the fingerprint of nuclear combustion, a low mass and a very high speed; all these facts imply that it must come from some kind of nearby binary system and that it must have undergone thermonuclear ignition. They have been a kind of supernova, but kind we haven’t seen before. “

The high speed could be explained if both stars in the binary were driven in opposite directions to their orbital speeds in a sort of slingshot maneuver after the explosion.

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POT

Scientists were also able to measure the star’s mass, which is particularly low for a white dwarf, only 40% of the mass of our Sun, which would be consistent with a partial supernova that did not destroy the star.

The nature of the nuclear combustion that occurs in a supernova is different from the reactions that release energy in nuclear power plants or in most nuclear weapons. Most uses of nuclear energy on Earth depend on fission, which breaks down the heaviest elements into light, rather than the fusion that occurs in a star.

“The process that takes place during a thermonuclear supernova is very similar to what we are trying to accomplish on Earth at our future power plants: the nuclear fusion of lighter elements into heavier elements, which releases large amounts of energy,” said the Professor Gänsicke to BBC News.

“In a fusion reactor, we use the lightest element, hydrogen (more specifically, different flavors or isotopes of it). In a thermonuclear supernova, the density and temperature in the star become so high that the fusion of heavier elements, starting with carbon and oxygen as ‘fuel’, and merging heavier elements. “

The best studied thermonuclear supernovae are classified as Type Ia. These helped discover dark energy, and are now routinely used to map the structure of the Universe. But there is increasing evidence that thermonuclear supernovae can occur under very different conditions.

SDSSJ1240 + 6710 may be the survivor of a type of supernova that has not yet been observed while it is happening.

Without the radioactive nickel that fuels the long-lasting glow of Type Ia supernovae, the explosion that sent the white dwarf through our galaxy would have been a brief flash of light that would have been difficult to detect.

The research has been published in the Monthly Notices of the Royal Astronomical Society.

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