‘Cosmic cannibalism’: Astronomers observe dead star ripping up an entire planetary system

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A star is ending its life so violently that the dead star left behind, called a white dwarf, is disrupting an entire planetary system by sucking in debris from both its inner and outer reaches. This cosmic phenomenon is the first time that astronomers have observed. The white dwarf star is consuming the rock-metallic and icy material, both of which are the “ingredients of planets”.

This case of cosmic cannibalism was diagnosed with the help of archival data from the Hubble Space Telescope and other NASA observatories. The researchers obtained the findings based on the analysis of material captured by the atmosphere of the nearby white dwarf star G238-44. A white dwarf is formed when a low-mass star like our sun exhausts most of its nuclear fuel. It is usually very dense and about the size of a planet.

“We have never seen both of these kinds of objects accreting onto a white dwarf at the same time. By studying these white dwarfs, we hope to gain a better understanding of planetary systems that are still intact,” said Ted Johnson, lead researcher and University of California, Los Angeles (UCLA) graduate, in a press statement.

These research findings are also interesting because it is such icy objects are credited for crashing into dry rocky planets in the solar system and “irrigating them”. Such comets and asteroids are believed to have delivered water to Earth billions of years ago, thereby sparking the conditions necessary for life as we know it.

Johnson added that the makeup of the bodies attracted by the white dwarf implies that such icy reservoirs might be common among planetary systems.

“Life as we know it requires a rocky planet covered with a variety of elements like carbon, nitrogen, and oxygen. The abundances of the elements we see on this white dwarf appear to require both a rocky and a volatile-rich parent body – the first example we’ve found among studies of hundreds of white dwarfs,” said Benjamin Zuckerman, UCLA professor and co-author, in the press statement.

Current planetary system evolution theories describe the transition of a red giant star to a white dwarf as a chaotic process. These stars quickly lose their outer layers and the orbits of their planets change dramatically. Small objects like asteroids and dwarf planets can end up getting too close and sent plummeting towards the star.

This new study confirms the nature of this violent and chaotic phase and showed that within 100 million years after the beginning of their white dwarf phase, stars are able to simultaneously capture and consume material from regions similar to our asteroid belt and Kuiper belt. But the estimated total mass consumed by the white dwarf in this research may be no more than the mass of an asteroid or small moon.

This white dwarf’s cannibalism presents a unique opportunity to allow scientists to observe what they were made of when they first formed around the star. The research team measured the presence of nitrogen, oxygen, magnesium, silicon, iron and other elements.

The researchers are now looking at the ultimate scenario for the Sun’s evolution, about 5 billion years from now. The Earth might get completely vaporised with the other inner planets. But the orbits of many asteroids in the main asteroid belt will be gravitationally perturbed by Jupiter and will eventually fall into the sun.

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