Free Astronomy Magazine September-October 2022

33 SEPTEMBER-OCTOBER 2022 ASTRO PUBLISHING lent chaotic phase, showing that within 100 million years after the beginning of its white dwarf phase, the star is able to simultaneously capture and consume material from its asteroid belt and Kuiper belt-like regions. The estimated total mass eventually gobbled up by the white dwarf in this study may be no more than the mass of an asteroid or small moon. While the presence of at least two objects that the white dwarf is con- suming is not directly measured, it’s likely one is metal-rich like an aster- oid and another is an icy body simi- lar to what’s found at the fringe of our solar system in the Kuiper belt. Though astronomers have cataloged over 5,000 exoplanets, the only planet where we have some direct knowledge of its interior makeup is Earth. The white dwarf cannibalism provides a unique opportunity to take planets apart and see what they were made of when they first formed around the star. The team measured the presence of nitrogen, oxygen, magnesium, sili- con and iron, among other ele- ments. The detection of iron in a very high abundance is evidence for metallic cores of terrestrial planets, like Earth, Venus, Mars and Mercury. Unexpectedly high nitrogen abun- dances led them to conclude the presence of icy bodies. “The best fit for our data was a nearly two-to- one mix of Mercury-like material and comet-like material, which is made up of ice and dust,” Johnson said. “Iron metal and nitrogen ice each suggest wildly different condi- tions of planetary formation. There is no known solar system object with so much of both.” T his illustration shows a white dwarf star siphoning off debris from shattered objects in a planetary system. The Hubble Space Telescope detects the spec- tral signature of the vaporized debris that revealed a combination of rocky- metallic and icy material, the ingredients of planets. The findings help describe the violent nature of evolved planetary systems and the composition of its dis- integrating bodies. [NASA, ESA, Joseph Olmsted (STScI)] !