Beware the vampire suns! Weird-looking blue straggler stars stay young by feeding off their stellar neighbours

Scientists have discovered how a type of strange type of old star manages to retain a deceptively youthful appearance – by eating its neighbour.

The stars, known as blue stragglers, have long-intrigued astronomers with their youthful looks. 

The strange distant suns appear brighter and bluer than typical stars as they age.

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Researchers believe they have discovered how a group of mysterious stars called blue stragglers manage to look far younger than they really are. They have found the stars siphon off the mass of other nearby bloated red giant stars, using their material to keep them burning bright and blue (illustrated in artists impression)

But scientists at the University of Wisconsin-Madison think they have uncovered why blue stragglers retain their youthful glow. 

They have found the stars use a nifty interstellar trick, slowly feeding on their nearest neighbour by siphoning off its mass.

Previously, the group had identified that more than three-quarters of these stars exist in pairs, as part of a binary star system.

After a couple hundred million years, the red giant star is burned out and collapses into a white dwarf that shines intensely in ultraviolet wavelengths. The companion star has bulked up on hydrogen siphoned from the red giant to become much hotter, brighter and bluer - making it appear young again (illustrated)

Using images from the Hubble Space Telescope, they honed in on a number of blue stragglers.

Analysis of the ultraviolet light emitted by one star 5,500 light years away, revealed that they appear to be partnered with a white dwarf – a small, brightly burning elderly star.

These findings deviate from the standard model of what a standard star is 'supposed to do' as it ages.

White dwarfs form when a star loses its outer atmosphere. 

But the researchers believe that rather than burning off, the star's outer atmosphere may have been siphoned off by a partnering blue straggler.

They say it appears as binary systems age, the more massive of the two stars begins to swell, growing into a red giant. 

The blue stragglers parasitise their partners, effectively feeding off the ageing star.

The Hubble Space Telescope is able to peer deep into the cosmos to snap images of the private lives of stars, capturing them as they are burst into life, explode or burn themselves out (stock images of a cluster of brown dwarfs in the Orion Nebula is pictured)

After a couple hundred million years, the red giant star burns out and collapses into a white dwarf that shines intensely in ultraviolet wavelengths. 

The companion vampire star has bulked up on hydrogen siphoned from the red giant to become much hotter, brighter and bluer - making it appear young again

Importantly, these vampire stars could account for as much as 25 per cent of all stars.

Professor Robert Mathieu, an astronomer from the University of Wisconsin-Madison who led the study, said that the findings could greatly expand our knowledge of the way stars evolve.

'For the evolution of single stars like our sun, by and large, we got it right, from birth to death,' he said.

'Now we're starting to do the same thing for the one-quarter of stars that are close-orbiting binaries.'

'This work allows us to talk not about points of light, but about the evolution of galaxies, including our own Milky Way. That's a big deal, and getting it right is an even bigger deal.'

The findings are published in the Astrophysical Journal.