The planetary debris was tracked to a ring of rubble around a white dwarf star some 410 light-years or 2,410,236,400,000,000 miles from Earth. Astronomers at the University of Warwick, Coventry, said the lucky fragment survived the death of its host star, dubbed SDSS J122859.93+104032.9. The white dwarf is believed to have once been twice as heavy as our Sun until it ran out of fuel and exploded. Surprisingly, the surviving planet’s fragment weathered the “system-wide” cataclysm enough to leave a sizeable portion behind.
Rich in elements like iron and nickel, the planet’s heavy metal composition likely helped the alien world partially live on.
The discovered fragment, or planetesimal, is now hurtling around the white dwarf at a rate of once every two hours, which comes as another surprise.
Astronomers would typically expect anything within such close proximity to a star to be torn apart and consumed.
Instead, Warwick’s astronomers traced a ring of gas emitted by the planetary debris using the Gran Telescopio Canarias in the Canaries, Spain.
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Space discovery: Astronomers found the surviving fragment of dead planet (Image: GETTY)
The planetesimal is estimated to measure at least 3,280ft (one kilometre) across but could be as large as “a few hundred kilometres in diameter”.
The astronomers presented their findings in the peer-reviewed journal Science.
Study co-author, Professor Boris Gaensicke from Warwick’s Department of Physics, said: “The planetesimal we have discovered is deep into the gravitational well of the white dwarf, much closer to it than we would expect to find anything still alive.
“That is only possible because it must be very dense and or very likely to have internal strength that holds it together, so we propose that it is composed largely of iron and nickel.
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“If it was pure iron it could survive where it lives now, but equally it could be a body that is rich in iron but with internal strength to hold it together, which is consistent with the planetesimal being a fairly massive fragment of a planet core.
Five to six billion years from now, our Solar System will be a white dwarf
“If correct, the original body was at least hundreds of kilometres in diameter because it is only at that point planets begin to differentiate – like oil on water – and have heavier elements sink to form a metallic core.”
When a star like the Sun spends all of its fuel, it expands and sheds its outer layers in a spectacular but cataclysmic death.
A dying star about 10 times as big as the Sun expands in its death throes and turns into a so-called red giant, which can be millions of miles across.
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Space news: The heavy metal planet partially survived the deaths of its host star (Image: UNIVERSITY OF WARWICK/MARK GARLICK)
A smaller star will shed all of its outer layers and collapse in on itself, forming an incredibly dense white dwarf star core.
Lead author Dr Christopher Manser, from Warwick’s Department of Physics, said: “The star would have originally been about two solar masses, but now the white dwarf is only 70 percent of the mass of our Sun.
“It is also very small – roughly the size of the Earth – and this makes the star, and in general all white dwarfs, extremely dense.
“The white dwarf’s gravity is so strong – about 100,000 times that of the Earth’s – that a typical asteroid will be ripped apart by gravitational forces if it passes too close to the white dwarf.”
Space news: The Sun will also day in five to six billion years (Image: GETTY)
Astronomers believe the discovery will help better understand what will happen to our Sun and the Earth a few billion years into the future.
Scientists believe the Sun will die anywhere between five to six billion years from now and destroy our home planet in the process.
According to Dr Manser, Earth stands no chance of surviving but planets like Mars might escape the cataclysm.
He said: “The general consensus is that five to six billion years from now, our Solar System will be a white dwarf in place of the Sun, orbited by Mars, Jupiter, Saturn, the outer planets, as well as asteroids and comets.
“Gravitational interactions are likely to happen in such remnants of planetary systems, meaning the bigger planets can easily nudge the smaller bodies onto an orbit that takes them close to the white dwarf, where they get shredded by its enormous gravity.”