NASA scientists discover oldest and coldest white dwarf star

India   Today
ASA-led Backyard Worlds: Planet 9 project has found the white debris J0207 which is located around 145 light-years away in the constellation Capricornus.

NASA has yet again made a breakthrough research by finding the coldest and oldest white dwarf, an Earth-sized remnant of a Sun-like star that has died, covered with dust and debris. It is also suspected that this is the first time a white dwarf, with multiple dust rings has been discovered.

Who discovered white debris?

A group of scientists working with the NASA-led Backyard Worlds: Planet 9 project has found the white debris.

J0207 was found through Backyard Worlds: Planet 9, a project led by Marc Kuchner, a co-author and astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, that asks volunteers to sort through WISE data for new discoveries.

Relevance of white debris:

The star, LSPM J0207+3331 or J0207 for short, 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. “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.”

Features of white debris

The white debris J0207 is located around 145 light-years away in the constellation Capricornus.

White dwarfs slowly cool as they age, and Debes’ team calculated J0207 is about 3 billion years old based on a temperature just over 10,500 degrees Fahrenheit (5,800 degrees Celsius).

A strong infrared signal picked up by NASA’s Wide-field Infrared Survey Explorer (WISE) mission – which mapped the entire sky in infrared light – suggested the presence of dust, making J0207 the oldest and coldest white dwarf with dust yet known.

When a Sun-like star runs out of fuel, it swells into a red giant, ejects at least half of its mass, and leaves behind a very hot white dwarf.

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.

How does white debris come into existence?

Over the course of the star’s giant phase, planets and asteroids close to the star become engulfed and incinerated. Planets and asteroids farther away survive, but move outward as their orbits expand. That’s because when the star loses mass, its gravitational influence on surrounding objects is greatly reduced.

Scientists think the dust around white debris may arise from distant asteroids and comets kicked closer to the star by gravitational interactions with displaced planets.

As these small bodies approach the white dwarf, the star’s strong gravity tears them apart in a process called tidal disruption. The debris forms a ring of dust that will slowly spiral down onto the surface of the star.

“We built Backyard Worlds: Planet 9 mostly to search for brown dwarfs and new planets in the solar system,” Marc Kuchner said. “But working with citizen scientists always leads to surprises. They are voracious – the project just celebrated its second birthday, and they’ve already discovered more than 1,000 likely brown dwarfs. Now that we’ve rebooted the website with double the amount of WISE data, we’re looking forward to even more exciting discoveries.”


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