An X-ray signal that has puzzled scientists for 45 years was the "death knell" of a planet ripped apart by a white dwarf star, data from NASA's Chandra observatory has revealed.

The Veil Nebula is roughly 2,400 light-years away in the constellation Cygnus. It is the remnants of a star that was roughly 20 times as big as our sun and exploded about 10,000 years ago.