Timeline for How did astronomers at Edwin Hubble time decide the size of the Milky Way Galaxy and settled the Great Debate?
Current License: CC BY-SA 4.0
8 events
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| Sep 23, 2021 at 11:12 | comment | added | Qiulang 邱朗 | Hi I did some further research about globular clusters (I am a layman) I still don't understand why the location of globular clusters can be defined as the edge of Milky Way. I also updated my question. | |
| Sep 22, 2021 at 9:01 | comment | added | John Rennie | @Qiulang the Milky Way does not have a well defined edge because the density of visible matter like stars tapers off gradually as we move outwards, and the density of dark matter tapers off even more slowly. So the "size" depends on how you define the where the edge is. Shapley defined the edge to be the location of the globular clusters, so measuring the distance to the globular clusters defined the distance to the edge. The article you link discusses how much bigger the Milky Way is if we change the definition of the "edge" to include the dark matter. | |
| Sep 22, 2021 at 8:51 | comment | added | Qiulang 邱朗 | Thanks again. Coincidentally I recently read an article sciencealert.com/…, so if "Astronomers Think They Just Found The Edge of The Milky Way Galaxy" in 2020 how did Shapley determine the edge of Milky Way back then. Sorry I seem to raise another question. | |
| Sep 22, 2021 at 8:46 | history | edited | John Rennie | CC BY-SA 4.0 |
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| Sep 22, 2021 at 8:39 | comment | added | John Rennie | @Qiulang I have extended my answer to explain what the experiments done at the observatory were and how they established the distance. | |
| Sep 22, 2021 at 8:38 | history | edited | John Rennie | CC BY-SA 4.0 |
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| Sep 22, 2021 at 7:43 | comment | added | Qiulang 邱朗 | Hi thanks for answering my question and actually that was what I thought: if we can find some Cepheid variable star that has 31 days period and it is much brighter than the one Edwin Hubble observed in Andromeda then we can safely concluded Andromeda is another galaxy. But I would like to know if astronomers at Edwin Hubble time actually did that ? (And hence my question). | |
| Sep 22, 2021 at 7:32 | history | answered | John Rennie | CC BY-SA 4.0 |