German NASA citizen scientist finds oldest, coldest white dwarf star

Melina Thevenot, a volunteer scientist also called citizen scientist working with NASA's Backyard Worlds: Planet 9 project, has found the oldest and coldest known white dwarf star, the US space administration has announced. The star named J0207 is an earth-sized remnant of a Sun-like star that has died and is ringed by dust and debris. It is located 145 light years away in the Capricornus constellation. Due to its temperature of 5,800 degrees Celsius (10,500 Fahrenheit), NASA believes the star is about 3 billion years old. The findings were published in The Astrophysical Journal Letters. 

NASA said in a statement on Tuesday that Thevenot's discovery "is forcing researchers to reconsider models of planetary systems and could help us learn about the distant future of our solar system."

"This white dwarf is so old that whatever process is feeding material into its rings must operate on billion-year timescales," said John Debes, an astronomer at the Space Telescope Science Institute in Baltimore, working with the NASA-led Backyard Worlds: Planet 9 project. 

"Most of the models scientists have created to explain rings around white dwarfs only work well up to around 100 million years, so this star is really challenging our assumptions of how planetary systems evolve," Debes added as reported by news agency IANS.

White dwarfs slowly cool as they age, and Debes's team calculated J0207 is about three billion years old, based on a temperature just over 5,800 degrees Celsius. 

Previously, dust disks and rings had only been observed surrounding white dwarfs about one-third J0207's age.

J0207's ring may even be multiple rings. Debes and his colleagues suggest there could be two distinct components - one thin ring just at the point where the star's tides break up the asteroids and a wider ring closer to the white dwarf. 

Thevenot, a citizen scientist from Germany, had been searching for brown dwarfs, which are larger than planets but smaller than stars, while working in the European Space Agency's archives when she found something much brighter and much further away.

Follow-up with future missions like NASA's James Webb Space Telescope may help astronomers tease apart the ring's constituent parts.

"That is a really motivating aspect of the search," said Thevenot as part of NASA's statement. "The researchers will move their telescopes to look at worlds you have discovered. What I especially enjoy, though, is the interaction with the awesome research team. Everyone is very kind, and they are always trying to make the best out of our discoveries."

Kuchner, the leader of the Backyard Worlds project, said working with citizen scientists "always leads to surprises."

(With inputs from agencies)