White dwarf stars have been imaged moving in mass numbers for the first time, in an event astronomers are describing as an exodus. This new finding could reveal the secrets of dying stars.
Globular cluster 47 Tucanae, where the phenomenon is seen taking place, is approximately 120 light years in diameter, and the collection of stars lies roughly 16,700 light years from our own planet. The cluster of hundreds of thousands of stars, located in the constellation Tucana (The Toucan), is barely visible to the unaided eye under the dark skies of the Southern Hemisphere.
White dwarfs are the corpses of dead stars which were once about the same size as our own sun. They are just the size of planets, and extremely dim over wavelengths of visible light. However, the surfaces of these remnants of stars soon after they die are extremely hot, so they glow brightly in ultraviolet frequencies. Without fuel to continue glowing, these stellar remains cool quickly over time, causing the peak energy recorded from the object to change frequency. Be studying the wavelength of this peak emission, astronomers can determine the age of the object.
The Hubble Space Telescope was used to record the new images of around 3,000 white dwarfs which shows the movement of the stellar remains as they moved from the crowded core of the cluster to the less populated "suburbs" of 47 Tucanae. How far a collapsed star moves during these migrations is dependent on its mass.
"We've 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," Jeremy Heyl of the University of British Columbia said.
As the white dwarfs continue to move away from the core toward the periphery of the globular cluster, they will cool over time. The stellar corpses, like bodies being carried to a cemetery, will arrive at their final resting spots in the outer reaches of the cluster in a few hundred million years.
White dwarfs that began their migrations just 6 million years ago were seen in the new photos, as well as some 100 million years in the past.
Analysis of this new image could assist astronomers in better understanding the processes that result in the loss of mass from a dying star. Roughly 100 million years before morphing into a white dwarf, a doomed star becomes a massive red giant. Before now, most astronomers believed the bodies lost a majority of their mass at this stage. The discovery of the young dwarfs in this cluster seems to contradict this theory.
Study of the white dwarf exodus in 47 Tucanae seen by the Hubble Space Telescope was profiled in The Astrophysical Journal.
