In the year 1006, our ancestors witnessed the biggest natural light show in
recorded history. A new “guest star,” as Chinese astronomers called it,
appeared one night without warning. It was brighter than a crescent moon
and visible in daytime. As months passed, the star dimmed until it was no
longer visible over a year later.
Today, we know the guest star of 1006 was a supernova. The most violent
explosions known, supernovas can briefly outshine the rest of a galaxy. The
most common ones happen when a massive star starts to run out of fuel.
Running on fumes, it can’t keep up enough internal pressure to balance out
the intense gravitational forces of its tremendous mass. As a result, its
core collapses into a neutron star or a black hole, taking most of the star
out with it.
Supernovas are rare; less than 1 percent of all stars are big enough for
such a fiery death. (Our relatively small sun will fade away gracefully as
a white dwarf.) In a galaxy the size of our Milky Way, though, astronomers
estimate roughly one or two supernovas should still light up per century.
Yet the last supernova observed in our galaxy was in 1604 — more than four
centuries ago. The telescope wasn’t even around yet!
We’re long overdue, and there’s always a chance a new guest star could
grace the heavens this very night. It would be the astronomical event of
the century. So, what would happen then?