David Meyer on Nostr: #onthisday in 1925 Edwin Hubble announced that Andromeda (aka M31) and other spiral ...

#onthisday in 1925 Edwin Hubble announced that Andromeda (aka M31) and other spiral nebulae were actually separate galaxies outside the Milky Way [1]. He based his conclusion on observations made by Vesto Slipher and Milton Humason, as well as relying on Henrietta Swan Leavitt’s work on Cepheid variables [2].

Interestingly (and despite some opposition), the then 35 year old Hubble first published his findings on galaxies in The New York Times on November 23, 1924, and only later presented them to other astronomers at the January 1, 1925 meeting of the American Astronomical Society. Hubble's results were not published in a peer-reviewed scientific journal until 1929 [3].

Hubble showed us that the universe is more than just our little island of stars and is in fact far greater in extent than what many astronomers of the day had allowed themselves to imagine.

[Image credit: https://apod.nasa.gov/apod/ap130626.html]

References
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[1] "Edwin Hubble Expands our View of the Universe", https://www.aps.org/archives/publications/apsnews/200801/physicshistory.cfm

[2] "Henrietta Swan Leavitt", https://en.wikipedia.org/wiki/Henrietta_Swan_Leavitt

[3] "Edwin Hubble", https://en.wikipedia.org/wiki/Edwin_Hubble

#hubble #andromeda #m31 #cosmology #nsasa