date of publication :
Wednesday
09:17 2022-11-9
Astronomers have identified the oldest star in our galaxy that is collecting debris from planetesimals, making it one of the oldest rocky and icy planetary systems discovered in the Milky Way.
The findings of the team, led by the University of Warwick, were published in the monthly issue of the Royal Astronomical Society, and concluded that a faint white dwarf located 90 light-years from Earth, in addition to the remnants of its planetary system orbiting it, are more than 10 billion years old. .
It is known that the fate of most stars, including those similar to our Sun, is to become a white dwarf. A white dwarf is a star that has burned up all its fuel and shed its outer layers and undergoes a process of shrinkage and cooling.
During this process, any orbiting planets will be disabled and, in some cases, destroyed, leaving their debris to collect on the surface of the white dwarf.
Scientists have now discovered, one of the oldest rocky planetary star systems in our galaxy, which consists of two white dwarf stars and the remains of rocky planets more than 10 billion years old.
The team found the two white dwarf stars about 90 light-years from Earth, their color changing due to material from former rocky planets, which was likely destroyed by the stars’ red giant phase.
For this study, the team of astronomers modeled two unusual white dwarfs discovered by the European Space Agency’s GAIA space observatory. Both stars are contaminated with planetary debris, with one found to be unusually blue, while the other is the faintest and redder so far found in the local galactic region, and the team subjected both to further analysis.
Using spectroscopic and photometric data from GAIA, the Dark Energy Survey and the European Southern Observatory’s X-Shooter instrument to work out how long it has cooled, the astronomers found that the “red” star WDJ2147-4035 is about 10.7 billion years old, of which 10.2 billion years were spent in Cooling as a white dwarf.
Spectroscopy involves analyzing light from a star of different wavelengths, which can detect when elements in a star’s atmosphere absorb light of different colors and help determine and quantify the elements present.
By analyzing the spectrum of WDJ2147-4035, the team found the minerals sodium, lithium, potassium and carbon initially detected on the star – making this the oldest mineral-contaminated white dwarf discovered to date.
The second “blue” star WDJ1922+0233 is slightly smaller than WDJ2147-4035 and was contaminated with planetary debris of similar composition to Earth’s crust.
The scientific team concluded that WDJ1922+0233’s blue color, despite its cold surface temperature, was caused by an unusually mixed atmosphere of helium and hydrogen.
Debris in the near-pure, highly gravitational atmosphere of red star WDJ2147-4035 is from an ancient planetary system that survived the star’s evolution into a white dwarf, leading astronomers to conclude that this is the oldest planetary system discovered around a white dwarf in the Milky Way.
“The red star WDJ2147-4035 is a mystery, because the accumulating planetary debris is very rich in lithium and potassium, and unlike anything known in our solar system, this is a very interesting white dwarf,” University of Warwick doctoral student in physics and lead author of the study, Abigail Elms, said in a statement. Its extremely cold surface temperature, the minerals that pollute it, its age, and the fact that it is magnetic make it extremely rare.”
“These metal-tainted stars show that Earth is not unique: there are other planetary systems with planetary bodies similar to Earth,” Elms added, noting that there are also other stars in the same life path as our sun, destined to become white dwarfs. “Cold white dwarfs consist of the oldest stars in our galaxy, and provide information on the formation and evolution of planetary systems around the oldest stars in the Milky Way,” she said.
Professor Pierre-Emmanuel Tremblay from the Department of Physics at the University of Warwick said: “When these ancient stars formed more than 10 billion years ago, the universe was less metal-rich than it is now, because minerals are formed in advanced stars and giant starbursts. The two white dwarfs that were made provide Their observation is an exciting window into planet formation in a mineral-poor, gas-rich environment that was different from conditions when the solar system formed.”