Free Astronomy Magazine September-October 2022

32 SEPTEMBER-OCTOBER 2022 ASTRO PUBLISHING remains of a star like our Sun after it sheds its outer layers and stops burning fuel though nuclear fusion. “We have never seen both of these kinds of objects accreting onto a white dwarf at the same time,” said Ted Johnson, the lead researcher and recent University of California, Los Angeles (UCLA) bachelor’s grad- uate. “By studying these white dwarfs, we hope to gain a better un- derstanding of planetary systems that are still intact.” The findings are also intriguing be- cause small icy objects are credited for crashing into and “irrigating” dry, rocky planets in our solar sys- tem. Billions of years ago comets and asteroids are thought to have delivered water to Earth, sparking the conditions necessary for life as we know it. The makeup of the bod- ies detected raining onto the white dwarf implies that icy reservoirs might be common among planetary systems, said Johnson. “Life as we know it requires a rocky planet covered with a variety of ele- ments like carbon, nitrogen, and oxygen,” said Benjamin Zuckerman, UCLA professor and co-author. “The abundances of the elements we see on this white dwarf appear to re- quire both a rocky and a volatile-rich parent body – the first example we’ve found among studies of hun- dreds of white dwarfs.” Theories of planetary system evolu- tion describe the transition between a red giant star and white dwarf phases as a chaotic process. The star quickly loses its outer layers and its planets’ orbits dramatically change. Small objects, like asteroids and dwarf planets, can venture too close to giant planets and be sent plum- meting toward the star. This study confirms the true scale of this vio- by NASA/ESA Claire Blome Dead star caught ripping up planetary system A star’s death throes have so violently disrupted its plan- etary system that the dead star left behind, called a white dwarf, is siphoning off debris from both the system’s inner and outer reaches. This is the first time as- tronomers have observed a white dwarf star that is consuming both rocky-metallic and icy material, the ingredients of planets. Archival data from NASA’s Hubble Space Telescope and other NASA ob- servatories were essential in diag- nosing this case of cosmic cannibal- ism. The findings help describe the violent nature of evolved planetary systems and can tell astronomers about the makeup of newly forming systems. The findings are based on analyzing material captured by the atmos- phere of the nearby white dwarf star G238-44. A white dwarf is what