Just 90 light-years from earth, the oldest dead start recognized to have supported a system of rocky planets, has been found. This discovery sheds light on the makeup of planets that originated nearly 11 billion years ago. The start is a white dwarf, WDJ2147-4035, a stellar corpse whose core ran out of hydrogen fuel. It is one of two white dwarfs contaminated by exoplanet debris recently found in the information recorded by the European Space Agency’s Gaia galactic civilization mission. It was born as a regular star 10.7 billion years ago, or 3 billion years after the Big Bang.
These are the oldest white dwarfs discovered to be accumulating debris from what appears to be a planetary destruction derby, though they are not the first. As such, they offer insightful information on the makeup of planets which originated when the cosmos was less than 3 billion years old.
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While the parent star of WDJ2147-4035 was much more massive than the sun, it was not super massive enough to go supernova at the close of its existence. Instead, the start ran out of hydrogen fuel for nuclear fusion in its center half a million years after its creation, or roughly 10.2 billion years ago, and grew large enough to transform into a red giant. It subsequently expelled its outer layers to reveal a white dwarf, an inactive star rich in helium.
Some of the circling planets were either crushed or disturbed. In contrast, others may have survived undamaged due to the star’s fluctuating gravitational fields as it went through its red giant phase. Orbiting planetary debris has been descending onto the white dwarf as a consequence of the disruptions in either case, which caused significant volumes of it.
