The oldest star in our universe is one of the oldest rocky and icy planetary systems discovered in the universe.
They found that a faint white dwarf located 90 light years from Earth and the remains of its planetary system are over 10 billion years old.
Our sun is at risk of becoming a white dwarf. A white dwarf is a star that has burned up all of its fuel and is going through a process of cooling and shrinks. During this process, planets will be disrupted and some will be destroyed, with their debris leaving a trail on the white dwarf's surface.
Two white dwarfs that were detected by the space observatory GAIA of the European Space Agency were modeled by the team of astronomer. One of the stars is blue and the other is red, but both are polluted by planetary debris and subjected to further analysis.
The "red" star WDJ2147-4035 is around 10 billion years old and has been cooling for some time.
When elements in the star's atmosphere absorb light at different colors, it is possible to determine what elements are and how much is there. The oldest metal-polluted white dwarf discovered so far was found by the team when they analyzed the spectrum from WDJ2147-4035).
The second "blue" star, WDJ1922+0233 is only slightly older than WDJ2147-4035 and was polluted by planetary debris. Despite its cool surface temperature, the blue color of WDJ1922+0233 is caused by the mixed helium-hydrogen atmosphere.
The debris found in the atmosphere of the red star WDJ2147-4035 is from an old planetary system that survived the evolution of the star into a white dwarf.
"These metal-polluted stars show that Earth isn't unique, there are other planetary systems out there with planetary bodies similar to the Earth," said the lead author. White dwarfs are so common around the universe that they are very important to understand. Cool white dwarfs formed from the oldest stars in our galaxy give information on the formation and evolution of planetary systems around the oldest stars.
The oldest stellar remnants are polluted by once Earth- like planets. It's amazing to think that the planets died a long time before the Earth was formed.
Astronomers can use the star's spectrum to determine how quickly those metals are sinking into the star's core, which will allow them to look back in time and determine how much of those metals were in the original planetary body. In the case of WDJ2147-4035, we can guess at what those planets would have looked like before the star died and became a white dwarf, but it's difficult.
The red star WDJ2147-4035 is a mystery as the planetary debris are very lithium and potassium rich. The fact that it is magnetic makes it extremely rare, as it is an interesting white dwarf that has an ultra-cool surface temperature.
The universe was less metal-rich when stars formed more than 10 billion years ago. The two white dwarfs give an exciting window into planetary formation in a metal poor and gas rich environment that was different to the conditions when the solar system was formed.
Abbigail Elms and his team analyzed ultra-cool white dwarfs polluted by planetary debris.
Journal information: Monthly Notices of the Royal Astronomical Society
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