Astronomers find white dwarf with two rings of planetary debris

Astronomers have spotted a white dwarf with planetary debris arranged in two distinct rings, a configuration not seen in similar systems previously observed.

The discovery

The white dwarf, named J1328−1450, is located in the Milky Way roughly 1,600 light-years from Earth, in the constellation Virgo. A light-year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km). The observations were made using the European Southern Observatory's Chile-based Very Large Telescope.

Prior to this discovery, astronomers had identified 21 white dwarfs with debris surrounding them, all of which had a single disc and not a double ring of material as the new observations reveal.

Possible surviving bodies

The researchers said the disc may have been shaped by two planetary or smaller rocky bodies that are embedded in the rings after managing to survive the star's violent death throes. The surviving planetary bodies may be remnants of larger and heavily disrupted planets. One of them may be around the size of the dwarf planet Pluto, with the other one smaller than that.

"It shows that the remnants of a planetary system can have a much more complex structure than we previously thought, and provides further support to the idea that planetary rocky bodies may survive the transformation of a star into a white dwarf," said astronomer Felipe Lagos-Vilches of Universidad Técnica Federico Santa María in Chile, one of the authors of the study published in the journal Nature Astronomy.

The white dwarf has a mass about 47 per cent that of the sun, jam-packed into a diameter roughly the same as that of Earth.

The presence of the two bodies may help explain the distribution of the surrounding material into a pair of concentric gaseous rings, Lagos-Vilches said. "The outer ring is strongly depleted in magnesium compared with the inner ring. This suggests that they may originate from different parent bodies, or possibly from different layers of a rocky body that was disrupted when it went too close to the white dwarf due to its strong gravitational field," Lagos-Vilches said.

A glimpse of the future

In about 5 billion years, the sun will become a red giant, Lagos-Vilches said. It will eventually lose its outer layers and become a white dwarf. The inner solar system will be dramatically affected. Mercury and Venus are expected to be engulfed by the expanding sun, while there is still no clear consensus on whether Earth will also be engulfed during this phase. The fate of the outer planets is different. Jupiter, Saturn and the 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.

"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," Lagos-Vilches said.

Why it matters

The finding suggests that the remains of a planetary system can have a more complex structure than previously thought and may offer a peek into one possible outcome for our solar system in the distant future.

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Sources

• channelnewsasia.com: Astronomers spot white dwarf star with two rings of planetary debris - CNA
• economictimes.indiatimes.com: A dead star has two rings of planetary debris; one may be hiding a Pluto-sized survivor - The Economic Times

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