A team of experts conducted a revolutionary research on white dwarfs, detecting the emission of X-rays on their surface due to the collision of planetary debris, a finding that changes the conception of these objects. “A white dwarf that accumulates planetary material from X-ray observations”, is the name of the research that will change the conception that exists about these compact objects. Dr. Odette Toloza, FONDECYT researcher of the Physics Department of the Universidad Técnica Federico Santa María and researcher of the Millennium Nucleus of Planetary Formation, contributed in the realization of this research that will significantly impact the world of science.
In conjunction with the Department of Physics of the University of Warwick, United Kingdom, Tim Cunningham led this research, which was published in the prestigious journal Nature and was supported by the Planetary Formation Millennium Nucleus (NFP) and the Department of Astronomy of the University of Michigan, United States.
White dwarfs are the final phase of a star with a mass less than eight times the size of the Sun. They are produced when the fusion process in its core is exhausted, that is to say, the hydrogen runs out. When this phenomenon occurs, the upper layers of the star seek to consume the remains of the remaining hydrogen, giving rise to a gravitational collapse. Likewise, these stellar remnants have a gravity so great that a person would be 1,000,000 times heavier. As a consequence, their chemical elements are stratified, iron and other heavy elements are found in the center and lighter elements are located on the surface. As a result, the core of these stars is extremely dense and the upper layers are scattered.
Due to the strong gravity, when a planet approaches a white dwarf, it shatters, decomposing into debris and orbiting around it in the form of rings. “For this reason, the study of white dwarfs is fundamental to understand the future of the stars and, therefore, of our own Solar System, in order to understand what will happen to the Earth in 4.5 billion years,” said Toloza.
The research considered observational evidence based on spectroscopy techniques and analysis of the ultraviolet wavelength range of the white dwarf. In addition, the team of experts also relied on existing optical X-ray and tomographic analyses that examined the distribution of gas around the remnant star.
This pioneering study was based on the observation of the G29-38 system, which has captivated the attention of astronomers for decades, detecting the presence of a planetary debris disk around the white dwarf. In this regard, the researchers also located x-ray emission produced by the collision between the gas from the outer disks and the white dwarf. When the gas hits the surface of the white dwarf it creates a plasma with temperatures of 100,000-1,000,000,000 degrees Kelvin, and to cool this plasma high-energy X-ray photons are emitted which can be detected with Chandra, NASA’s space satellite.
“This is the first time this work has been done and the presence of material impacting the white dwarf has been detected. It is an important observation that will allow us to obtain measurements of the accretion rate that is independent of models and therefore allows us to corroborate whether our measurement techniques are correct,” said Toloza.
Regarding the impact that this finding will have for the scientific community, the researcher added that “astronomy is advancing, discovering new planets, but this is the science that is telling us what is going to happen to them”. In relation to the new opportunities that this discovery opens, the physicist explains that “now we are working on the modeling of the white dwarf and in answering new questions about the movement of gas that is occurring within it”.