One of the oldest rocky and icy planetary systems yet observed in the Milky Way has been identified as the oldest star in our galaxy that is accreting debris from orbiting planetesimals.
According to their research, a dim white dwarf that is only 90 light-years away from Earth and the remnants of its orbital planetary system are both more than ten billion years old. The research, which was led by the University of Warwick, was released on November 5 in the Royal Astronomical Society's Monthly Notices.
The majority of stars, including our Sun, will eventually become white dwarfs. A star that has run out of fuel, shed its outer layers, and is currently contracting and cooling is known as a white dwarf. During this process, any planets in orbit will be disturbed and, in some cases, destroyed, and their debris will be left behind to accrete onto the white dwarf's surface.
Two unique white dwarfs found by the European Space Agency's GAIA space observatory were modelled by the researchers for this study. Planetary waste has harmed both stars. One of them was discovered to be extraordinarily blue, whereas the other is the most flimsy and reddest object discovered thus far in the nearby galactic neighborhood. The scientific team conducted additional examination on both.
The WDJ2147-4035 red star's debris, which was discovered in its otherwise nearly pure-helium and high-gravity atmosphere, came from an ancient planetary system that endured the star's transformation into a white dwarf, leading astronomers to claim that this is the oldest planetary system around a white dwarf ever found in the Milky Way.
The study's lead author, PhD candidate Abbigail Elms at the University of Warwick's Department of Physics, said: "These metal-polluted stars demonstrate that Earth is not the only planetary system with planets that resemble our own. White dwarves are so common in the universe—97% of all stars will eventually turn into them—that it's crucial to comprehend them, especially those that are this fantastic. Cool white dwarfs, which were created from the oldest stars in our galaxy, shed light on how planetary systems formed and developed around the oldest stars in the Milky Way.
In the Milky Way, we are discovering the oldest star remains that have been contaminated by former Earth-like planets. It's incredible to consider that this occurred 10 billion years ago, long before the Earth was even formed, and that those planets perished.
We can infer the characteristics of such planets from their abundances by comparing them to celestial objects and planetary material found in our own solar system, but in the case of WDJ2147-4035, this has proven difficult.
The accreted planetary debris are particularly lithium and potassium-rich and unlike anything known in our own solar system, which makes the red star WDJ2147-4035 mysterious, according to Abbigail. This white dwarf is especially intriguing because of its exceptionally low surface temperature, metal contamination, advanced age, and magnetic nature.
The abundance of each metal in the original planetary body can be determined by looking back in time using the star's spectra, which can be used to gauge how quickly those metals are sinking into the star's core.
As metals are created in evolved stars and enormous stellar explosions, Professor Pier-Emmanuel Tremblay of the University of Warwick's Department of Physics stated: "When these old stars originated more than 10 billion years ago, the universe was less metal-rich than it is now. The two detected white dwarfs offer an intriguing view into planetary formation in an environment that was distinct from the one in which the solar system formed—one that was rich in gas and deficient in metal.
Abbigail K. Elms, Pier-Emmanuel Tremblay, Boris T. Gänsicke, Detlev Koester, Mark A. Hollands, Nicola Pietro Gentile Fusillo, Tim Cunningham, and Kevin Apps published "Spectral analysis of ultra-cool white dwarfs polluted by planetary debris" in Monthly Notices of the Royal Astronomical Society on November 5, 2022.
Reference: 10.1093/mnras/stac2908
The European Research Council's Horizon 2020 research and innovation program, the Leverhulme Trust Grant, and the UK STFC consolidated grant all provided support for this study.
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