Distance to the Andromeda Nebula (Öpik)
Distancia a la nebulosa de Andrómeda (Öpik)
- Date
- 1922 · confidence high
- Place
- Tartu, Tartu County, Estonia
- Credited to
- Ernst Öpik
- Field
- Cosmos & Earth
What was discovered
From the observed rotation speed and the luminosity, the Estonian astronomer calculated a distance to Andromeda of about 450 kiloparsecs. It was still a rough estimate, but it placed the nebula clearly outside the Milky Way.
Öpik's figure (about 1.5 million light-years) fell short of today's 2.5 million; the method was ingenious but the decisive determination was Hubble's with Cepheids (1924-1925).
What it led to
- evidence that spiral nebulae are independent galaxies
- the mass–luminosity method for estimating distances
- the Shapley–Curtis debate settled by Hubble with Cepheids in 1924-1925