Astronomers discover a chunk of a planet’s core around a long-dead star

White dwarfs are weird objects. These dense cores of dead stars pack as much mass as the Sun into a body about the size of Earth. They’re left behind when a small- to mid-sized star ends its life by ballooning into a red giant and blowing off its outer layers in a series of explosive pulses. Although these puffs of ejected material eventually create a beautiful and expansive cloud of glowing gas called a planetary nebula, the process unfortunately tends to wreak havoc on any planets residing nearby.

Considering the Sun is destined to become a white dwarf in about 5 billion years, this scenario doesn’t bode well for Earth. However, there’s a growing dossier of evidence that suggests some planetary systems — including our own solar system — might be able to survive their host star’s violent transition into a white dwarf. At least in part.

In a new study published today in the journal Science, a team of researchers reported the discovery of one of the first small and intact planetary fragments (or planetesimals) found orbiting in the gas-filled debris disk of a white dwarf star. Because this strange object is composed of mainly iron, nickel, and other heavy metals, the researchers think it’s most likely an ancient remnant that split from the core of a rocky planet similar to Earth or Mars. By studying such objects in other systems, researchers hope to eventually piece together the evolution and ultimate fate of our own solar system.

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