In the framework of the project – Backyard Worlds: Planet 9, in search of still unknown worlds in the outer borders of the Solar System, amateur astronomers discovered the oldest and coldest white dwarf surrounded by rings.
When the star, similar to the Sun, runs out of fuel, it turns into a red giant, which later throws at least half of its mass into space and leaves behind a very hot white dwarf. During the expansion phase of a star, planets close to it and asteroids are absorbed and burned, and distant worlds survive, but gradually begin to move away from the dying star, moving to more distant orbits. This happens when the gravitational influence on the objects surrounding the star decreases during its loss of mass.
This white dwarf is so old that the process of feeding material into its rings must go on for billions of years. However, most models created to explain rings around white dwarfs work only on a time interval of about 100 million years, so this star really casts doubt on our assumptions about how planetary systems develop.
-John Debes, lead author of the research Institute of Space Telescope in Baltimore (USA)
Such a scenario describes the future of the solar system. After about 5 billion years, Mercury, then Venus and, possibly, the Earth will be absorbed when the Sun turns into a red giant. For hundreds of thousands or millions of years, the inner part of the system will be cleared, and the rest of the planets will go to outer regions.
However, some white dwarfs, from 1 to 4 percent, show infrared radiation, indicating that they are surrounded by dust disks or rings. Scientists believe that dust is the remnants of asteroids and comets torn apart by tidal destruction, which lived far from the star but were thrown at it by escaping planets.
However, the white dwarf LSPM J0207 + 3331, which is 145 light-years from Earth in the direction of the Capricornus constellation and glows very brightly in the infrared, does not fit even this small percentage. Over 3 billion years, it has cooled to a temperature of 5800 degrees Celsius, which makes J0207 the oldest and coldest white dwarf, surrounded by dust and rings. Previously, such structures were observed only around white dwarfs under the age of one billion years.
Now, astronomers will have to explain the presence of dust and rings in orbit J0207. At the same time, scientists believe that a white dwarf found may even have two rings: one thin in a place where tidal forces destroy asteroids, and a wider one closer to the star.
Initially, there is a constant flow of material. Planets hurl asteroids inward to a white dwarf, which crumble to support a disk of dust. But over time, the asteroid belt is depleted, like sand grains in an hourglass. In the end, all the material on the disk falls on the surface of the white dwarf, so the older ones, such as J0207, have very little chance of being surrounded by rings.
-John Debes
Amateur astronomers have discovered an ancient white dwarf surrounded by mysterious rings
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