Astronomers led by the University of Warwick have identified the oldest star in the Galaxy because it accumulates debris from orbiting planets.
The discovery was announced on November 5 in the Monthly Notice of the Royal Astronomical Society, concluding that a faint white dwarf star located 90 light years from Earth, along with the rest of the planetary system orbiting it, is more than 10 billion years old. It is one of the oldest rocky and icy planetary systems discovered in the Milky Way.
Most stars, including stars like the Sun, will eventually become white dwarfs. A white dwarf is a star that has burned all of its fuel and is undergoing a process of contraction and cooling. During this process, all orbiting planets will be disrupted and in some cases destroyed, with debris accumulating on the white dwarf’s surface.
White dwarfs WDJ2147-4035 and WDJ1922+0233
The white dwarfs WDJ2147-4035 and WDJ1922+0233 are surrounded by orbiting planetary debris.
In the new study, a team of astronomers modeled two unusual white dwarfs discovered by the European Space Agency’s GAIA space observatory. Both stars are contaminated by planetary debris. One of them turned out to have an unusual blue color, while the other star was dark and red.
Using spectroscopic and photometric data from GAIA to determine how long it takes for stars to cool, astronomers discovered “red” star WDJ2147-4035 approximately 10.7 billion years, of which 10.2 billion years spent cooling as a white dwarf star. By analyzing the spectrum of WDJ2147-4035, the team discovered the metals sodium, lithium, potassium and carbon accumulated on the star, making it a oldest white dwarf contaminated by metals discovered so far.
The second “blue” star WDJ1922 + 0233 is only slightly younger than WDJ2147-4035 and is contaminated by planetary debris similar in composition to Earth’s continental crust. The science team concluded that WDJ1922+0233’s blue color is due to its unusual mixed helium-hydrogen atmosphere.
The debris found in the nearly pure atmosphere of the star WDJ2147-4035 comes from an ancient planetary system that existed after the star evolved into a white dwarf. Astronomers have concluded that it is the oldest planetary system around a white dwarf star discovered in the Milky Way.
Lead author Abigail Elms from the University of Warwick’s Department of Physics said: “These metal-contaminated stars show that Earth is not unique; there are other planetary systems with planetary bodies similar to Earth. 97% of all stars will become white dwarfs and they are everywhere in the universe, so it’s important to know about them. They provide information on the formation and evolution of planetary systems around the oldest stars in the Milky Way.
Astronomers can also use the star’s spectrum to determine how quickly these metals enter the star’s core. This allowed them to go back in time to determine the abundance of each of these metals in the original planetary body.
“By comparing this abundance with celestial bodies and materials found in the solar system, we can predict what these planets would have looked like before the star died and became a white dwarf. It’s amazing to think that this happened on a scale of 10 billion years and that these planets died before Earth formed. » » said Abbigail Elms.
According to Abbigail, the red star WDJ2147-4035 is a mystery because the accumulated planetary debris is rich in lithium and potassium, unlike anything known in the solar system. It is a very interesting white dwarf star because its surface temperature is extremely cold. Additionally, the list of contaminating metals, its age, and the fact that WDJ2147-4035 is magnetic make it extremely rare.
Professor Pier-Emmanuel Tremblay from the Department of Physics at the University of Warwick said: “When these stars formed more than 10 billion years ago, the universe was less rich in metals than it is today, because metals formed during evolving stars and giant stellar explosions. The two observed white dwarfs offer an exciting opportunity for planet formation in a metal-poor, gas-rich environment, different from the formation conditions of the solar system..
Article source: 1thegioi
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Astronomers led by the University of Warwick have identified the oldest star in the Galaxy as an accumulation of debris from orbiting planets…