Field guide · Deep sky
NebulaSupernova remnant
The wreckage of an exploded star, still racing outward thousands of years later. The iron in your blood was forged in explosions like these.
- Made by
- A massive star’s core collapsing
- Expands at
- Thousands of km per second
- Leaves behind
- A neutron star or a black hole
A star many times the Sun’s mass ends not with a puff but with a collapse: its core falls in on itself in under a second and the rest of the star is blown out at a few percent of the speed of light. For weeks it can outshine an entire galaxy.
The debris keeps going, ploughing into the gas around it and glowing for tens of thousands of years. The Crab Nebula is the remnant of a star Chinese astronomers saw explode in July 1054 — bright enough to see in daylight for three weeks. At its centre spins a neutron star, the crushed core, turning thirty times a second.
Supernovae are how the universe spreads heavy elements. Much of the oxygen you are breathing and the iron in your blood was made inside stars and scattered by explosions like this one.
See it in the sky
Each one opens the sky map pointed at it, for tonight, from where you are.