Free Astronomy Magazine July-August 2019

30 JULY-AUGUST 2019 SPACE CHRONICLES variations in the emitted light to identify additional gas that the plan- etesimal is generating. Using OSIRIS spectrograph, installed in the Gran Telescopio Canarias (GTC), situated in the Roque de los Muchachos Observatory (Garafía, La Palma), the scientists studied a de- bris disc orbiting a white dwarf 410 light years away formed by the dis- ruption of rocky bodies composed of elements such as iron, magne- sium, silicon, and oxygen − the four key building blocks of the Earth and most rocky bodies. Within that disc they discovered a ring of gas streaming from a solid body, like a comet’s tail. This gas could either be generated by the body itself or by evaporating dust as it collides with small debris within the disc. The astronomers estimate that this body has to be at least a kilometer in size, but could be as large as a few hundred kilometres in diameter, comparable to the largest asteroids known in the solar system. White dwarfs are the remains of stars like our sun that have burnt all their fuel and shed their outer lay- ers, leaving behind a dense core which slowly cools over time. This star has shrunk so dramatically that the planetesimal orbits within its sun’s original radius. Evidence sug- gests that it was once part of a larger body further out in its solar system and is likely to have been a planet torn apart as the star began its cooling process. Lead author, Christopher Manser, a Research Fel- low in the Department of Physics, said: “The star would have originally been about two solar masses, but now the white dwarf is only 70% of the mass of our Sun. It is also very small − roughly the size of the Earth − and this makes the star, and in A fragment of a planet that has survived the death of its star has been discovered in a disc of debris formed from de- stroyed planets which the star ulti- mately consumes. The discovery was made by a group of astron- omers led by the University of War- wick and involving research staff from the IAC and ULL. The iron and nickel rich planetesimal survived a system-wide cataclysm that fol- lowed the death of its host star, SDSS J122859.93+104032.9. Believed to have once been part of a larger planet, its survival is all the more astonishing as it orbits closer to its star than previously thought possible, going around it once every two hours. As reported in the jour- nal Science, is the first time that scientists have used spectroscopy to discover a solid body in orbit around a white dwarf, using subtle by IAC Heavy metal planet fragment survives destruction from dead star