A dying star’s final act was to destroy all of its planets

When white dwarfs go wild, their planets suffer the resulting chaos. The evidence later shows up in and around the dying star’s atmosphere after it engulfed planetary and cometary debris. That’s the conclusion a team of UCLA astronomers came to after examining the nearby white dwarf G238-44 in detail. They found a case of cosmic cannibalism at this dying star, about 86 light-years from Earth.

If this star were in the location of our sun, it would absorb the remains of planets, asteroids and comets up to the Kuiper Belt. This sprawling buffet makes this outstanding act of cannibalism one of the most widespread ever seen.

“We’ve never seen these two types of objects accumulate on a white dwarf simultaneously,” said lead researcher Ted Johnson, a UCLA physics and astronomy graduate student. “By studying these white dwarfs, we hope to gain a better understanding of planetary systems that are still intact.”

Find evidence of chaos at a dying star

Johnson was part of a team from UCLA, UC San Diego and the University of Kiel in Germany working to study chemical elements detected in and around the white dwarf’s atmosphere. They used data from NASA’s decommissioned Far Ultraviolet Spectroscopic Explorer, the high-resolution Echelle spectrometer at Keck Observatory in Hawaii, and the Hubble Space Telescope’s Cosmic Origins Spectrograph and Space Telescope Imaging Spectrograph. The team found and measured the presence of nitrogen, oxygen, magnesium, silicon and iron, among other elements.

Iron is particularly interesting because it forms the cores of rocky planets such as Earth and Mars. Its presence is an indication that terrestrial worlds once orbited G238-44. The presence of large amounts of nitrogen suggests that the system also had an accumulation of ice bodies.

When white dwarfs strike

When stars like the Sun get very old, they leave behind burned-out cores called white dwarfs. Over billions of years, these remnants of dying stars slowly cool. Before they get to that point, however, the actual death spasms can be quite violent and chaotic. Then they cannibalize the worlds around them. The discovery of the “remnants” of these planets, comets and asteroids in the atmosphere of G238-44 paints an ominous picture of the future of our solar system.

We can assume that our sun will go through the process from about five billion years. First, it will rise to become a red giant, potentially engulfing planets into Earth’s orbit. Then it loses its outer layers and forms what we call a “planetary nebula”. Once everything is scattered into space, what remains is the massive but tiny white dwarf.

The entire process will tear apart the solar system, tearing planets apart and scattering comets and asteroids. Any of these objects that come too close to the white dwarf Sun will be sucked in and destroyed. The extent of the destruction occurs fairly quickly, if the example of G238-44 is any indication. This study shows the shocking extent of the chaos. Within 100 million years of entering its white dwarf phase, the dying star was able to capture and consume material from its nearby asteroid belt and distant Kuiper belt-like regions.

What else does this white dwarf reveal

This finding not only shows what lies in our future, but also provides interesting insights into the formation of other systems. It offers clues as to what they contain and a glimpse into the past of our own solar system. For example, astronomers believe that icy objects in our own young solar system have slammed into dry, rocky planets. This is in addition to the rocky materials that helped create our planet. For G238-44, that makes for an interesting amalgamation of stuff from a variety of regions, and the evidence shows it.

“The best fit for our data was an almost two-to-one mix of Mercury-like material and comet-like material composed of ice and dust,” Johnson said. “Ferrous metal and nitrogen ice each point to completely different conditions of planet formation. There is no known object in the solar system with so much of both.”

A dying star gives other clues

The death of this sun-like star and its propensity to devour debris has another interesting twist. Billions of years ago, comets and asteroids probably brought water to our planet, creating the conditions necessary for life. According to Benjamin Zuckerman, UCLA professor of physics and astronomy, the combination of icy and rocky material that rained on G238-44 shows that other planetary systems may have icy reservoirs (like the Kuiper Belt and the Oort Cloud). This is in addition to rocky bodies like Earth and asteroids.

“Life as we know it requires a rocky planet covered in a variety of volatile elements such as carbon, nitrogen and oxygen,” Zuckerman said. “The abundance of elements we see on this white dwarf appears to come from both a rocky and ephemeral parent body — the first example we’ve found among studies of hundreds of white dwarfs.”

It’s fascinating to imagine that our own sun could do the same in a few billion years. Perhaps a future astronomer will conduct the same study as Johnson and his team on a planet a few dozen light-years away — and discover what remains of Earth in the dying glow of the white dwarf Sun.

For more informations

Dead Star’s cannibalism in its planetary system is the most widespread ever observed

Dead star caught ripping apart planetary system