They identify the oldest star in the Milky Way

The red  star WDJ2147-4035 is over 10,000 years old and is accumulating debris from planets that were destroyed in its orbit.


Astronomers led by the University of Warwick have identified the oldest star in the Milky Way that accumulates debris from orbiting planetesimals.

This makes it one of the oldest discovered rocky and icy planetary systems in the galaxy.

The findings, published this Saturday in the Monthly Notices of the Royal Astronomical Society , conclude that a faint white dwarf located 90 light-years from Earth, as well as the remains of its orbiting planetary system, are more than 10 billion years old.

The fate of most stars , including those like the Sun, is to become a white dwarf, which is a star that has used up all of its fuel and shed its outer layers and is now going through a process of shrinking and shrinking. cooling. During this process, the orbiting planets will be disrupted and, in some cases, destroyed, with their remains accumulating on the surface of the white dwarf.

For this study, the team of astronomers, led by the University of Warwick, modeled two unusual white dwarfs that were detected by the European Space Agency’s GAIA space observatory . Both stars are contaminated by planetary debris, and one was found to be unusually blue, while the other is the faintest and reddest found to date in the local galactic neighborhood; the team subjected both to further analysis.

Using spectroscopic and photometric data from GAIA, the Dark Energy Survey and the X-Shooter instrument at the European Southern Observatory to determine how long it has been cooling, astronomers found that the ‘red’ star WDJ2147-4035 is about 10.7 billion years old, of which 10.2 billion years have been spent cooling as a white dwarf.

Spectroscopy involves analyzing the star ‘s light at different wavelengths, which can detect when elements in the star’s atmosphere are absorbing light in different colors and help determine which elements are and how much is present. Analyzing the spectrum of WDJ2147-4035 , the team found the presence of the tentatively detected metals sodium, lithium, potassium, and carbon accreting in the star , making it the oldest metal-contaminated white dwarf yet discovered.

The second ‘blue’ star WDJ1922+0233 is only slightly younger than WDJ2147-4035 and was contaminated by planetary debris of a similar composition to Earth’s continental crust. The science team concluded that WDJ1922+0233 ‘s blue color , despite its cool surface temperature, is caused by its unusual mixed atmosphere of helium and hydrogen.

The remains found in the high-gravity, near-pure helium atmosphere of red star WDJ2147-4035 are from an ancient planetary system that survived the star ‘s evolution to a white dwarf, leading astronomers to conclude that this is the oldest planetary system around a white dwarf discovered in the Milky Way .