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Cepheid variable star?

  1. Apr 17, 2008 #1
    Cepheid variable star???

    How was Hubble able to determine that one of these stars was within what was then called a nebula?

    You're telling me that back in the early 1900's, he was able to detect a single star within a distant galaxy???
  2. jcsd
  3. Apr 17, 2008 #2
    A supernova explosion is so bright that it can outshine entire galaxy. Not only that, it can shine for a couple of weeks before dimming. That can give an astronomer plenty of time to find it in the sky and analyze it.
  4. Apr 17, 2008 #3
    Didn't Hubble use Cepheids, and not supernovas, to deduce the distance to galaxies?
  5. Apr 17, 2008 #4


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    Well, since Cepheids are variable stars, some of them are very big and get very bright, which yes, was visible with telescopes in the early 1900's. I imagine that after noticing the predictable period, he discerned it was a Cepheid and was able to use it as a "standard candle"
  6. Apr 17, 2008 #5
    Here are a couple of links that show images that Hubble used:
    http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/galaxies.htm" [Broken]
    http://www.ottawa.rasc.ca/features/marchHubble/index.html" [Broken]
    Last edited by a moderator: May 3, 2017
  7. Apr 17, 2008 #6
    Great links, thanks.
    Last edited by a moderator: May 3, 2017
  8. Apr 18, 2008 #7


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    Hubble made an amazing discovery with relatively weak instruments - that other galaxies aside from the MW exist. Cepheids in the Andromeda galaxy [at a distance of about 3 million light years] were near the limit of detectability by instruments available to Hubble in the early 20th century. Modern instruments can detect cepheids out to around 60 million light years. It's still an exciting area of research. Studies indicate metallicity is an important variable in the absolute luminosity of Cepheids. Other distance indicators have helped calibrate Cepheid derived distances.
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