Sun’s death rattle may hurl comets out of solar system
A DYING star deserves a last hurrah. It is fitting then, that our sun will throw many of its comets into interstellar space when it dies, according to new simulations.
In about 5 billion years, the sun will run out of hydrogen to burn in its core and will expand to become a red giant star. The red giant will blow off its atmosphere, leaving an ember-like core called a white dwarf.
It is generally accepted that planets inward of Earth and possibly Earth itself will be engulfed and incinerated during the red giant phase. But astronomers have paid little attention to more distant objects.
Now a study suggests that the sun’s death throes will reverberate all the way to the vast swarm of comets called the Oort cloud, out beyond Pluto.
When the sun loses mass, its gravity will decrease. This change can eject orbiting objects, but only if it happens on a timescale not much longer than the object’s orbital period. At the very end of the sun’s red giant phase, astronomers think it will shed a sizeable fraction of its mass in just 100,000 years or so.
This would still be too gradual to eject the planets beyond Earth, but simulations show that it will cause the exit of up to 20 per cent of Oort cloud comets into interstellar space, say Dimitri Veras and colleagues at the University of Cambridge. The work is to be published in Monthly Notices of the Royal Astronomical Society.
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