(ORDO NEWS) — The same fate may await our planet. Now scientists have been able to see firsthand what will happen to the planet after the expansion of its star.
Turning into a red giant, the star absorbs the planets next to it. Those that survived could then be devoured by the white dwarf.
Many stars go supernova at the end of their lives, but this is far from the only way out. When a star runs out of fuel and becomes unstable, it swells to enormous size before shedding its outer shell as its core collapses into a small, super-dense white dwarf.
When the Sun becomes such a red giant, it will expand to the orbit of Mars and can destabilize and destroy planets that are close enough.
Scientists have already seen white dwarfs that have planets, which means they can survive this collapse. But increasingly, scientists are discovering that many exoplanets are being swallowed up by white dwarfs.
Planet eaten by a star
Now, astronomers have discovered the oldest known example of such a phenomenon: an exoplanet engulfed by a white dwarf that formed 10.2 billion years ago.
The white dwarf is about 90 light-years from Earth, incredibly small and dim, with an unusual shade of red, brighter than any other star of its type.
The second white dwarf, an unusually blue one, formed 9 billion years ago. The team found that both stars are constantly polluted by falling planetary debris.
However, while the red star, dubbed WD J2147-4035, is the oldest polluted white dwarf discovered, the blue star, dubbed WD J1922+0233, is potentially more interesting: the elements found in its atmosphere suggest that the star is eating a planet very similar to Earth.
In the case of WD J2147-4035, astronomers have determined that its contamination was likely caused by the remnants of a planetary system that orbited the star before dying, survived the stellar agony and is now slowly falling into the star over billions of years.
Since the star became a white dwarf over 10 billion years ago, this makes it the oldest known planetary system in the Milky Way (albeit decaying and disappearing).
Meanwhile, debris contaminating WD J1922+0233 has a composition similar to Earth’s continental crust, suggesting that an Earth-like planet orbits a sun-like star that lived and died billions of years before the formation of the solar system.
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