publication date :
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 results 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 lies 90 light-years from Earth, in addition to the remnants of its planetary system orbiting it. they are over 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 all of its fuel, lost its outer layers, and undergoes a shrinking and cooling process.
During this process, all orbiting planets will be disabled and, in some cases, destroyed, allowing 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, consisting of two white dwarf stars and the remains of rocky planets over 10 billion years old.
The team found the two white dwarfs about 90 light-years from Earth, whose color changed due to material from former rocky planets, which was likely destroyed by the red giant phase of the stars.
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, one of which has been found to be unusually blue, while the other is the faintest and redest found in the local galactic region so far, and the team subjected both to further analysis.
Using spectroscopic and photometric data from the GAIA, the Dark Energy Survey and the European Southern Observatory’s X-Shooter instrument to calculate how long it cooled, the astronomers found that the “red” star WDJ2147-4035 has about 10.7 billions of years, of which 10.2 billion years were spent in Cooling as a white dwarf.
Spectroscopy involves analyzing the light of 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 discovered the minerals sodium, lithium, potassium and carbon initially detected on the star, making it the oldest mineral-contaminated white dwarf discovered to date.
The second “blue” star WDJ1922 + 0233 is slightly smaller than WDJ2147-4035 and has been contaminated by planetary debris of similar composition to the 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.
The debris in the near pure and highly gravitational atmosphere of the red star WDJ2147-4035 comes 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 planetary debris that accumulates is very rich in lithium and potassium, and unlike anything else known in our solar system, this is a very interesting white dwarf,” he said. a doctoral student in physics from the University of Warwick. The study’s lead author, Abigail Elms, said in a statement. Its very cold surface temperature, the minerals that pollute it, its age and the fact that it is magnetic make it extremely rare. “
“These metal-contaminated stars show that the Earth is not unique: there are other planetary systems with Earth-like planetary bodies,” 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 are made up 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 of the Department of Physics at the University of Warwick said: “When these ancient stars were formed more than 10 billion years ago, the universe was less rich in metals than it is now, because the minerals are formed in advanced stars and giant stellar explosions. The two white dwarfs that were created provide their observation is an exciting window into planet formation in a mineral-poor, gas-rich environment that was different from conditions when one was formed the solar system “.
