Astronomers discover oldest dead star 90 light-years away from Earth
Astronomers have identified the oldest dead star, a white dwarf, in our Milky Way galaxy. It lies only 90 light-years from Earth and it was found accumulating debris from its orbiting planets. This makes it "one of the oldest rocky and icy planetary systems" to have been discovered. The findings were deduced from data collected by European Space Agency's (ESA) Gaia mission.
Why does this story matter?
The Gaia (Global Astrometric Interferometer for Astrophysics) mission was launched in 2013 and is expected to operate until 2025. One of its objectives is to generate a precise three-dimensional map of our galaxy by covering approximately two billion celestial objects. Significant information about the formation of other Earth-like rocky planets in our universe has been obtained from the space mission's most recent observations.
What is a white dwarf?
A white dwarf is a star that has shed its outer layers, leaving behind only the core. This is the fate of most stars, including the Sun, after they exhaust their nuclear fuel. The star then undergoes a process of shrinking and cooling. During this phase, orbiting planets are disturbed, and their remnants accumulate on the surface of the fiery body.
Scientists have discovered two white dwarfs
"We're finding the oldest stellar remnants in the Milky Way that are polluted by once Earth-like planets. It's amazing to think that this happened on the scale of 10 billion years and that those planets died way before the Earth was even formed," said Abigail Elms, the leader of the project. Spectroscopic data from Gaia led to the discovery of two white dwarfs.
Both stars are polluted by planetary debris
The first 'red' star, designated WDJ2147-4035, is the oldest metal-polluted white dwarf which contains sodium, lithium, and potassium. It is estimated to be 10.7 billion years old. The second 'blue' star is younger and is named WDJ1922+0233. The color is attributed to the unusual mixing of gases in its helium-hydrogen atmosphere. Further, its planetary debris has a similar composition to Earth's continental crust.
What insights have scientists gained from these discoveries?
"These metal-polluted stars show that Earth isn't unique, there are other planetary systems with planetary bodies similar to the Earth," Elms explained. "Formed from the oldest stars in our galaxy, cool white dwarfs provide information on the formation and evolution of planetary systems around the oldest stars in Milky Way," she added. This study was published in Monthly Notices of the Royal Astronomical Society.
