We know that space is full of mystery. Adding to the intrigue, astronomers recently found an ancient solar system that is very different from our cosmic home.
About 90 light-years away, researchers spotted a white dwarf star more than 10 billion years old — meaning the remaining hot core of a dead sun-like star — surrounded by a graveyard of broken planet fragments, called planetesimals. The faint star has pulled debris from these objects. But this solar system is unlike anything around us. Filled with elements such as lithium and potassium. The important thing is that no planet in our solar system has such a composition.
Why was this ancient solar system in our early galaxy so different? How did he become rich in these materials, which were rare at the time?
“It’s a complete mystery,” Abbigail Elms, a PhD student at the University of Warwick who researches white dwarfs, told Mashable. The research was published this week in the journal Science Monthly Notices of the Royal Astronomical Society.
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As noted above, this solar system is old. This means that the white dwarf (called WDJ2147-4035) and the surrounding solar system formed and died before the sun and Earth were even born. In fact, the pieces of former planets around WDJ2147-4035 are the oldest planets ever found in our galaxy around a white dwarf, Elms noted.
How do astronomers know what this ancient solar system consisted of?
They discovered this white dwarf and another of a similar age using an observatory in space called Gaia. While orbiting the sun, this distant spacecraft maps stars and galaxies in the world. After spotting these white dwarfs, the researchers turned to an instrument called the “X-Shooter,” located at a high altitude in Chile, to detect what is and isn’t in the stars’ atmospheres (the X-Shooter is a type of an extremely valuable astronomical tool called a “spectrometer”). In WDJ2147-4035, they found that chemicals like lithium, potassium, and sodium had accreted—or been pulled by gravity and clustered around the ancient star. White dwarfs are made of hydrogen or helium, so the rocky remnants of planets were responsible for providing the other unique elements, the researchers concluded (by running simulations of the evolution of this solar system).
An artist’s rendering of bits of planets (planetoids) orbiting white dwarf stars.
Credit: University of Warwick / Mark Garlick
Interestingly, the other white dwarf (WDJ1922+0233) they discovered was significantly different from the mystery one. It’s more intimate. They found that this star had pulled in planetary debris that is similar to Earth’s rocky crust. So while one solar system remains an anomaly, the other shows that Earth isn’t so unique in the universe: There are other solar systems out there just like it.
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These two solar systems, however, are littered with graveyards of former planets. More than 95 percent of stars like the sun evolve into white dwarfs. Near the end of their lives, they expand into colossal red giants, destroying or disrupting nearby objects. As our sun expands, it will gobble up planets like Mercury, Venus and perhaps even Earth before shedding its outer layers. Red giants will leave behind remnants of shattered planets and moons. The remaining star itself will be a white dwarf.
This is our cosmic fate. Just not for a long, long, long time.
“Our sun will evolve into a white dwarf in about 5 billion years.” Elms said.
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