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A suspected 'mass grave' of white dwarf stars has been found near the centre of the Milky Way.

Thousands of objects, believed to be dead stellar objects are thought to be orbiting the Galactic Centre.

But why there are so many of these stars here - which are left behind when a larger star runs out of fuel - remains a mystery.

Scientists at Haverford College in Pennsylvania say they have spotted X-ray emissions consistent with thousands of white dwarfs (one illustrated centre) at the galaxy's centre. These are stars left behind after larger ones use up their fuel. But why thousands of these stars are here remains a mystery

The finding, published in Nature, was made by scientists at Haverford College in Pennsylvania, US using Nasa's NuStar telescope.

When they peered at the Galactic Centre, they found an emission of X-rays that corresponded to thousands of dead stars being present.

The emission could also be due to millisecond pulsars - rapidly rotating neutron stars - or dense magnetic fields.

'However, all these interpretations pose significant challenges to our understanding of stellar evolution, binary formation and cosmic-ray production in the Galactic Centre,' the researchers wrote in their paper.

The emissions were found to be coming from a region of the Galactic Centre 13 by 26 light-years in size around the central supermassive black hole, called Sagittarius A*.

But it is the potential for these to be white dwarf stars that is the most intriguing theory.

There are already known to be many young, massive stars orbiting our galaxy's central supermassive black hole - but why there would be thousands of white dwarf stars as well is not clear.

White dwarfs are what are left when medium-mass stars - including our sun - shed their outer layers at the end of their life.

Shown is the region around the supermassive black hole at the Milky Way's Galactic Centre - Sagittarius A* - where the X-ray emissions consistent with thousands of white dwarfs were found. Other possible explanations include millisecond pulsars, which are rapidly rotating neutron stars

Nasa's NuStar telescope (illustrated) is a space-based X-ray telescope that focuses high-energy X-rays from distant astrophysical sources. Its primary goal is to conduct a survey for black holes, but it has also been used for other purposes such as this latest research

Behind is left the hot, dense core which burns white.

They are known to cause explosions, specifically Type 1a supernovas, when they form into a binary with a much larger star.

If the white dwarf gathers too much material from a companion, its mass will reach a critical point and the star will explode.

The researchers say the latest finding needs further study to get to the bottom of the mystery.