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Mount Wilson & Palomar Observatories, Andromeda Nebula (negative print),
+/- 1950, United States,
Stamp on the back,
Vintage silver print, Good,
Not mounted,
32,5 (33) X 33 cm
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Dr. Edwin Hubble (Marshfield, 20 november 1889 – San Marino (Californië), 28 september 1953) was lucky enough to arrive at Mt. Wilson soon after the 100-inch reflecting telescope was completed. A careful and hard-working observer, Hubble took many photographs of the same set of spiral nebulae (now called galaxies). Multiple images were needed in order to identify changes over time. He observed several novas, or instances in which a dim star became much brighter as it attracted material from a nearby companion star.
Then, on October 4, 1923, while comparing a photograph that he had just taken of the Andromeda galaxy with photos taken on previous nights, Hubble identified a Cepheid variable star—the one kind of star that could provide a means of determining the distance to the galaxy. Over the next several months Hubble determined that the star varied in brightness with a period of 31.45 days, which meant it was 7,000 times brighter than the Sun. Comparing its apparent brightness with its actual brightness Hubble determined that it was 900,000 light years away.
In 1929 Hubble published a paper that would lead to the realization that the universe was expanding.
Photo ID: 5825
