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Future Cannibal

May 6, 2018

A star system in Virgo is headed for an act of cannibalism. In 250 million years or so, one object in the system will begin consuming the other.

The system was discovered by the Kepler spacecraft, which hunts for planets in other star systems. The system consists of two objects. One is a white dwarf — the dead core of a star. The other is a brown dwarf. It’s too massive to be a planet, but not massive enough to shine like a star.

The pair probably formed about three billion years ago. The star was more massive than the Sun, so it burned through the nuclear fuel in its core faster than the Sun does. As it used up that fuel, the star expanded. It got so big that its outer layers enveloped the brown dwarf. That caused the “failed star” to spiral closer to the true star’s core.

The star eventually expelled its outer layers into space, leaving only its hot, dead core. It’s about 40 percent as heavy as the Sun, but no bigger than Earth.

The brown dwarf is closer to the star than the Moon is to Earth. At that range, the two objects orbit each other quickly, emitting gravitational waves in the process. That causes them to spin closer together. In about 250 million years, they’ll be so close that the white dwarf will start pulling gas off the brown dwarf. Every million years or so, enough gas may build up to trigger an explosion, called a nova — a process that may continue until the brown dwarf has been consumed by its dead companion.

Script by Damond Benningfield

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