A Dying Star Sent Out an SOS Pointing to Its Killer: A Buzz-Saw Black Hole

By Rafi Letzter, Staff Writer | January 10, 2019 05:21pm ET

Back when Earth's continents were mushed together into a single blob called Pangaea and reptiles were just beginning to overtake amphibians as the dominant life-forms on Earth, a star strayed too close to a black hole. The black hole was a buzz saw, spinning fast enough to stretch the star into a rotating ring around the black hole's event horizon, the point beyond which not even light can escape.

The star, under the influence of the black hole's enormous gravity, stopped being a star. Some star stuff whipped past the black hole and out into space. Other stellar material whirled in quick circles around the gravity well before falling into the black hole itself.

Something happened just before this material crossed the event horizon, though: A stream of X-rays shot out into space. They were the last signal from the dying star before it disappeared. [Spaced Out! 101 Astronomy Images That Will Blow Your Mind]

Then, for 290 million years, those X-rays flew through space. Meanwhile, on Earth, the continents broke apart. Dinosaurs arose, walked the planet, then went extinct. Mammals profilerated and gave rise to humans. Those humans built sky-watching machines, including the All-Sky Automated Survey for Supernovae (ASASSN), a group of telescopes scattered all over the planet. And on Nov. 22, 2014, the X-rays from that dying star landed in ASASSN's eye, and the instrument sent data about them down to scientists on Earth.

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