As I recall, the bulk of Hubble's data was studying and measuring red shift values, at least as far as the acceleration discoveries, IE the further the galaxy the faster it goes. Cepheids mainly being used to calibrate distance, small changes in cepheid values seem unlikely to change the acceleration discovery and the Hubble Constant. Science should always strive to improve measurements, which the clearly seem to be doing. What is the furthest galaxy a cepheid has been observed? Outside of our local group? Beyond the Virgo Cluster?
I imagine the sheer distance of cepheids in other galaxies makes it clear the star is in that galaxy and not ours. There are no stars in the space between galaxies after all. Good question, Steve. I would guess that eventually enough other Chepheids
in Andromeda were found to show a similar distance that the scientific consensus vindicated Hubble on that one. -- Joe
--- On Sat, 1/15/11, Stephen Peterson <scpki7l@gmail.com> wrote:
From: Stephen Peterson <scpki7l@gmail.com> Subject: [Utah-astronomy] Flickering Candles To: utah-astronomy@mailman.xmission.com Date: Saturday, January 15, 2011, 1:48 PM Joe, Well written blog! Also very impressed with Patrick's Cepheid photo 'in Andromeda'. One question that has always bothered me: How do we know that the star in question is indeed in or very near Andromeda? That is, for example, could it be half way there? When I look at really beautiful photos of Andromeda ( i.e. in SBIG's advertisement by Tony Hallas) it is easy to see clouds of stars but they, for the most part, appear unresolved as individuals. Have I missed some other confirming data?
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