New ‘Freak Star’ That Poses ‘Severe Challenge To Understanding Of Stellar Evolution’ Discovered

A team of German astronomers led by Professor Klaus Werner of the University of Tübingen have discovered a new kind of 'freak star' that is believed to be extremely rare.

The team was using the Large Binocular Telescope in Arizona when they spotted two particularly unusual stars.

What made them stand out so much was that their surface was covered in an unusually high amount of carbon and oxygen, with the surface consisting of about 20% or so of each element, both being a by-product of nuclear fusion using helium.

'Helium burning' kicks in once a star has used up all its reserves of hydrogen and only occurs when the star has grown old.

For comparison, our own sun is a gigantic nuclear furnace that fuses hydrogen into helium at temperatures of millions of degrees, right now the mass of our sun is about 73% hydrogen and 25% helium, with smaller amounts of other elements such as oxygen, carbon and iron.

For a star to have 20% worth of oxygen and carbon each on the surface and still show signs of nuclear fusion going on is impressive, and the experts have theorised that these new types of 'freak star' are formed from the merging of two white dwarfs, the remains of long-dead stars.

The idea that nuclear fusion is still happening despite the usual signs indicating it should have stopped by now is an exciting find for scientists.

It takes millions of years for a star to run through it's lifespan and die before shrinking to the size of a planet as it ends up as a white dwarf.

Professor Werner said, per MailOnline: 'We normally expect stars with the chemical surface composition of the stars discovered to have completed the helium fusion in their centres and to be in the final stages of becoming white dwarfs. These new stars are a severe challenge to our understanding of stellar evolution.'

As for what has caused this rare phenomenon is still up for debate among the scientific community, since we won't get the chance to see our own sun go through a similar process for about another five billion years when it runs out of hydrogen.

Astronomers at the University of La Plata in Argentina, published in Monthly Notices of the Royal Astronomical Society, believe the stars 'were formed by a very rare type of merging between two white dwarfs', and that 'for binary systems formed with very specific masses, a carbon- and oxygen-rich white dwarf might be disrupted and end up on top of a helium-rich one, leading to the formation of these stars'.

However, there is still as yet no full explanation.

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