Are many visible stars dead?

Twinkle twinkle little star, how I wonder how alive you are…

8th March 2016
Are many visible stars dead? (© Getty Images)

Asked by: William Simons, Southampton

Probably not. All of the stars you can see with the unaided eye lie within about 4,000 light-years of Earth. But the most distant ones are intrinsically brighter, have more mass and are therefore likely to die in rare supernova explosions.

We can only see fainter (and hence less massive) stars out to smaller distances and these stars are more likely to end their lives in less violent but more common deaths. This complicates the estimate of the ‘death rate’ for visible stars. But we can choose an intermediate distance, say 1,000 light-years, to estimate this number.

Using our knowledge of the death rate in the entire Milky Way, the death rate for visible stars works out at about one star every 10,000 years or so. Given that all those stars are closer than 4,000 light-years, it is unlikely – though not impossible – that any of them are already dead.