A team of astronomers using the NASA/ESA Hubble Space Telescope has, for the first time, collected a census of young white dwarf stars beginning their migration from the crowded center of an ancient star cluster to its less populated outskirts.
The new results challenge our ideas about how and when a star loses its mass near the end of its life.
White dwarfs are the burned-out relics of ancient stars that rapidly shut down their nuclear furnaces, cooling down and losing mass at the end of their active lives. As these stellar carcasses age and shed mass, they are expelled from the densely packed center of the globular cluster and migrate to wider orbits. Whilst astronomers knew about this process, they had never seen it in action, until now.
first author Jeremy Heyl of the University of British Columbia explained that they have seen the final picture before: white dwarfs that have migrated and settled into more distant orbits outside the core, determined by their mass, but in this study, which comprises about a quarter of all the young white dwarfs in the cluster, we're actually catching the stars in the process of moving outward and distributing themselves appropriately according to mass.
Co-author Elisa Antolini of the Universita degli Studi di Perugia said that before becoming white dwarfs, the migrating stars were among the most massive in the cluster, roughly as massive as the Sun.
Antolini added that the youngest white dwarfs were only just embarking on their journey. This could be evidence that the stars shed much of their mass at a later stage in their lives than we once thought, which is an exciting find.
The new results imply that the stars actually lose 40 to 50 percent of their bulk just 10 million years before completely burning out as white dwarfs.
