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Astronomers Discover 3-Billion-Year-Old Ringed White Dwarf

by AMNH on

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An illustration of LSPM J0207+3331 is a ringed cold white dwarf. LSPM J0207+3331 is a cold white dwarf surrounded by a ring of dusty debris.
NASA’s Goddard Space Flight Center/Scott Wiessinger

Not all discoveries are made by professionals. Sometimes, an amateur naturalist’s observations can lead to revelatory finds.

Case in point: a recent finding of an Earth-sized star with a ring of dust around it that researchers have calculated to be about 3 billion years old, by Melina Thévenot, a citizen scientist in Germany who has been working as a volunteer with the NASA-led crowdsourcing project Backyard Worlds: Planet 9. The star’s advanced age and surprising properties are challenging some of the current thinking about how planetary systems, including our solar system, evolve.

“The citizens involved in Backyard Worlds are the critical frontline of our research productivity. You need no scientific background to get involved yet many of our volunteers are so dedicated that they are as productive as scientific collaborators,” says Jackie Faherty, a senior scientist and senior manager of education at the Museum who is one of the researchers behind Backyard Worlds.

The project, which launched in February 2017, relies on about 50,000 volunteers across the world to scan images of NASA’s Wide-field Infrared Survey Explorer (WISE) mission to find new objects in the Sun’s backyard, including a potential Planet 9 in our own solar system. Backyard Worlds has already yielded other discoveries, such as a cold brown dwarf shortly after the project's launch. 

The latest discovery was sparked when Thévenot spotted the star, now known as LSPM J0207+3331, which was too bright to be a brown dwarf. Researchers confirmed that the planet-sized star, which is located 145 light-years away in the constellation Triangulum, is a white dwarf, an object that was Sun-like at one time but that we are seeing at the end of its lifecycle.

When researchers analyzed the star more closely, they found a strong infrared signal suggesting the presence of dust, which has only been observed in dwarfs one-third of J0207’s age. These surprising observations are offering new insights into the evolution of planetary systems—and a glimpse at what may happen in our own solar system in the distant future.

An GIF depicts an asteroid breaking apart from the gravitational force of a white dwarf.
An asteroid (bottom left) breaks apart under the powerful gravity of LSPM J0207+3331. Scientists think the system’s infrared signal is best explained by two distinct rings composed of dust supplied by crumbling asteroids.
Backyard Worlds: Planet 9/NASA’s Goddard Space Flight Center

“This white dwarf is so old that whatever process is feeding material into its rings must operate on billion-year timescales,” says John Debes, an astronomer at the Space Telescope Science Institute in Baltimore and lead author on a paper detailing the findings in The Astrophysical Journal Letters. “Most of the models scientists have created to explain rings around white dwarfs only work up to around 100 million years, so this star is really challenging our assumptions of how planetary systems evolve.”

“Working with citizen scientists always leads to surprises.”

At the end of its life, a Sun-like star will become a red giant and lose half its mass, leaving behind a hot white dwarf. In the red giant stage, planets nearest to it will be engulfed, and those objects farthest away will move outward as its gravitational pull is reduced. For some white dwarfs—between 1 and 4 percent—dust rings can form from distant asteroids and comets that are pushed into the star’s orbit through interactions with its displaced planets. That is what scientists have thought is most likely to happen in our own solar system in about 5 billion years.

But this scenario is complicated by J0207, which is pushing researchers to reconsider current models for white dwarf life cycles. Given its age, J0207 should be less likely to have dust or rings, which become depleted over time as material falls down onto the surface of the dwarf.

“We built Backyard Worlds: Planet 9 mostly to search for brown dwarfs and new planets in the solar system,” said Marc Kuchner, principal investigator for Backyard Worlds: Planet 9 and an astrophysicist at NASA’s Goddard Space Flight Center. “But working with citizen scientists always leads to surprises.”