Dark secret behind 'zombie' stars orbiting the Milky Way's supermassive black hole

The fate of stars close to the middle of our Milky Way galaxy has been revealed - and it's a rather sinister outcome.

Research undertaken by scientists at Northwestern University in Illinois has looked in to why some stars close to the supermassive black hole in the middle of our solar system look 'youthful'.

That is, they are old - some very old - but imagery of them has had some experts scratching their head for looking younger than their years. And it's by no means the only headache causer out there in space.

Nope, they've not turned to botox like many here on planet Earth. Instead, it sounds a lot more like something from a sci-fi horror.

Believe it or not, we're on about stars eating stars. Yep, full on gobbling up their neighbours.

And if they don't enjoy a bit of cosmic cannibalism, the outcome is being galactically conjoined in to one even bigger blot of energy.

Northwestern’s Sanaea C. Rose, who led the research, said: “A few stars win the collision lottery.

"Through collisions and mergers, these stars collect more hydrogen. Although they were formed from an older population, they masquerade as rejuvenated, young-looking stars.

"They are like zombie stars; they eat their neighbours.”

Rose and her colleagues studied the turbulent paths of 1,000 simulated stars orbiting around the supermassive black hole in the Milky Way's core, called Sagittarius A*.

By studying effects of these huge collisions in a simulation, the work - published this month - finds that collision survivors can lose mass to become stripped down, low-mass stars.

Alternatively they can merge with other stars to become massive and rejuvenated in appearance.

Rose said: "The region around the central black hole is dense with stars moving at extremely high speeds.

"It’s a bit like running through an incredibly crowded subway station in New York City during rush hour. If you aren’t colliding into other people, then you are passing very closely by them.

"For stars, these near collisions still cause them to interact gravitationally. We wanted to explore what these collisions and interactions mean for the stellar population and characterise their outcomes.”

The stars being subjected to this survive or die game of space roulette differ massively from our own star, the Sun.

For starters, there's no star near our Sun. The closest is roughly four light-years away.

For context, that same distance is filled with a million stars in the distance from the core of the Milky Way's supermassive black hole.

Rose said: "Stars, which are under the influence of a supermassive black hole in a very crowded region, are unlike anything we will ever see in our own solar neighbourhood.

"But if we can learn about these stellar populations, then we might be able to learn something new about how the galactic centre was assembled.

"At the very least, it certainly provides a point of contrast for the neighbourhood where we live.”

The research was presented on 4 April at the American Physical Society’s monthly meeting in California.

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