Astronomers have discovered a white dwarf star surrounded by an unusual configuration of planetary debris consisting of two distinct rings. The discovery, published in the journal Nature Astronomy, may offer a look into one possible outcome for our solar system in the distant future.
The white dwarf, identified as J1328-1450, is located in the constellation Virgo, roughly 1,600 light-years from Earth. Researchers observed the star using the Very Large Telescope in Chile, operated by the European Southern Observatory. The star has a mass approximately 47% that of the sun, compressed into a diameter roughly equal to that of Earth.
The researchers stated that the debris disc may have been shaped by two planetary or smaller rocky bodies that are embedded in the rings after surviving the star's violent death throes. These surviving bodies may be remnants of larger, heavily disrupted planets. One could be around the size of the dwarf planet Pluto, while the other is smaller than that.
Felipe Lagos-Vilches, an astronomer of Universidad Técnica Federico Santa María in Chile and one of the study's authors, said the original star may have hosted a planetary system before expanding into a red giant. He explained that while the expanding star may have engulfed some innermost planets, those with more distant orbits might have survived.
Lagos-Vilches said the planetary system did not completely disappear. He noted that some surviving rocky bodies may have been gravitationally perturbed onto highly eccentric orbits that brought them close to the white dwarf. Objects that came sufficiently close were disrupted by the white dwarf's gravitational force, spreading material into a debris disc of dust and gas. However, Lagos-Vilches said two relatively large rocky bodies may have survived within this debris.
The presence of these two bodies may explain why the surrounding material is distributed into a pair of concentric gaseous rings. Lagos-Vilches said the outer ring is strongly depleted in magnesium compared with the inner ring, suggesting they may originate from different parent bodies or different layers of a rocky body disrupted by the white dwarf's strong gravitational field.
Prior to this discovery, astronomers had identified 21 white dwarfs with debris surrounding them, but all of those featured a single disc rather than a double ring. Lagos-Vilches said the finding shows that the remnants of a planetary system can have a much more complex structure than previously thought and provides further support to the idea that planetary rocky bodies may survive the transformation of a star into a white dwarf.
Lagos-Vilches noted that in about 5 billion years, the sun will become a red giant and eventually become a white dwarf. He stated that Mercury and Venus are expected to be engulfed by the expanding sun, though there is no clear consensus on whether Earth will also be engulfed. He noted that Jupiter, Saturn, and more distant bodies should have a much better chance of surviving.
After the sun becomes a white dwarf, surviving planetary remnants, moons, and asteroids could potentially be drawn close enough to the white dwarf to be torn apart by gravitational forces. Lagos-Vilches said a debris disc like the one around J1328-1450 could therefore represent one possible stage in the very distant future of our own planetary system.
