Oldest Planetary Debris in Our Galaxy Found in New Study
mrpg writes:
https://phys.org/news/2022-11-oldest-planetary-debris-galaxy.html
Astronomers led by the University of Warwick have identified the oldest star in our galaxy that is accreting debris from orbiting planetesimals, making it one of the oldest rocky and icy planetary systems discovered in the Milky Way.
Their findings are published today (Nov. 5) in the Monthly Notices of the Royal Astronomical Society and conclude that a faint white dwarf located 90 light years from Earth, as well as the remains of its orbiting planetary system, are over 10 billion years old.
The fate of most stars, including those like our sun, is to become a white dwarf. A white dwarf is a star that has burnt up all of its fuel and shed its outer layers and is now undergoing a process of shrinking and cooling. During this process, any orbiting planets will be disrupted and in some cases destroyed, with their debris left to accrete onto the surface of the white dwarf.
[...] Using spectroscopic and photometric data from GAIA, the Dark Energy Survey and the X-Shooter instrument at the European Southern Observatory to work out how long it has been cooling for, the astronomers found that the "red" star WDJ2147-4035 is around 10.7 billion years old, of which 10.2 billion years has been spent cooling as a white dwarf.
[...] The second "blue" star WDJ1922+0233 is only slightly younger than WDJ2147-4035 and was polluted by planetary debris of a similar composition to the Earth's continental crust. The science team concluded that the blue color of WDJ1922+0233, despite its cool surface temperature, is caused by its unusual mixed helium-hydrogen atmosphere.
The debris found in the otherwise nearly pure-helium and high-gravity atmosphere of the red star WDJ2147-4035 are from an old planetary system that survived the evolution of the star into a white dwarf, leading the astronomers to conclude that this is the oldest planetary system around a white dwarf discovered in the Milky Way.
More information:
Abbigail K Elms, Pier-Emmanuel Tremblay, Boris T Gansicke, et al, Spectral analysis of ultra-cool white dwarfs polluted by planetary debris, Monthly Notices of the Royal Astronomical Society (2022). (DOI: 10.1093/mnras/stac2908)
Journal information: Monthly Notices of the Royal Astronomical Society
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