Despite providing a nurturing home for planets for billions of years, stars sometimes turn treacherous and eat their children. With time, the evidence of that filicide sinks into the core of a star, never to be visible again.
But now, astronomers have found a way to catch murderous stars red-handed and figured out how long we have until the case grows cold.
When stars get hungry
Stars can potentially kill (although astronomers prefer to use the more polite term “engulf”) their planets at a variety of stages in the stars’ life cycles. At one end of the cycle, when typical sunlike stars are about to die, they swell and turn red, becoming giant or supergiant stars.
Related: Scientists get gruesome look at how stars like our sun eat their own planets
When this happens, any inner worlds unlucky enough to be too close will be consumed. The outer planets of the system may suffer as well, as the shifting gravitational landscape caused by the dying stars’ convulsions can send planets careening into their parent star. This fate will befall our own solar system in about 4.5 billion years, when the sun will destroy Mercury, Venus and likely Earth.
But it’s not just fits of old age that can destroy a planet. It also happens when stars are young. The early formation days of a solar system are an especially violent time. The protostar at the center grows in both temperature and density — but fitfully, occasionally throwing off massive tantrum storms of plasma.
Meanwhile, the planets begin evolving around the temperamental star. Accreting from smaller building blocks, the planetesimals crash into each other, gravitationally destabilize each other and generally roughhouse as they attempt to become full-fledged planets. Naturally, all this commotion ejects some material from the system, with other material flowing into the still-forming star.
This influx of planet-building material into the central star can be slow or fast. In some cases, a steady trickle of heavy elements makes its way to the star over millions of years. In that case, it’s less a case of outright planetary murder and more like a slow strangulation of the ingredients needed to build more or bigger worlds around a star. In other cases, an entire planet crashes right into the star, disappearing completely in the blink of an eye.
The ferocious energy and searing temperature inside a star are more than enough to completely destroy a planet. And that’s assuming the planet even survives entry and isn’t…
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