HUBBLE

The Universe goes beyond the Milky Way galaxy

Edwin Hubble's arrival at Mount Wilson, California, in 1919 coincided roughly with the completion of the 100-inch (2.5 m) Hooker Telescope, then the world's largest telescope. At that time, the prevailing view of the cosmos was that the universe consisted entirely of the Milky Way Galaxy. Using the Hooker Telescope at Mt. Wilson, Hubble identified Cepheid variables (a kind of star; see also standard candle) in several spiral nebulae, including the Andromeda Nebula. His observations, made in 1922–1923, proved conclusively that these nebulae were much too distant to be part of the Milky Way and were, in fact, entire galaxies outside our own. This idea had been opposed by many in the astronomy establishment of the time, in particular by the Harvard University-based Harlow Shapley. Hubble's discovery, announced on January 1, 1925, fundamentally changed the view of the universe.
Hubble also devised the most commonly used system for classifying galaxies, grouping them according to their appearance in photographic images. He arranged the different groups of galaxies in what became known as the Hubble sequence.


HUBBLE 1925


Massive stars that breathe once
in months, half a million times
brighter than our sun
were what caught Hubble’s eye in 1922
especially the Andromeda nebula one:
this starry spiral he worked out must lie
beyond the Milky Way.

‘Beyond the Milky Way’
was like saying the earth is round
before Pythagoras 600 years in
front of Christ’s birth
or that the earth circles the sun
ere Copernicus did his sums
in De Revolutionibus in 1543.
Conventional wisdom was till then
that all there is to the universe
is contained in the Milky Way
but no. Hubble was the one to show
that galaxies exist beyond our own
spiking the myth again
that we live
at the centre of all things.

Hubble used the Hooker telescope
In California.