Posted on 07/01/2011 4:20:01 AM PDT by SunkenCiv
Explanation: In the 1920s, examining photographic plates from the Mt. Wilson Observatory's 100 inch telescope, Edwin Hubble determined the distance to the Andromeda Nebula, decisively demonstrating the existence of other galaxies far beyond the Milky Way. His notations are evident on the historic plate image inset at the lower right, shown in context with ground based and Hubble Space Telescope images of the region made nearly 90 years later. By intercomparing different plates, Hubble searched for novae, stars which underwent a sudden increase in brightness. He found several on this plate and marked them with an "N". Later, discovering that the one near the upper right corner (marked by lines) was actually a type of variable star known as a cepheid, he crossed out the "N" and wrote "VAR!". Thanks to the work of Harvard astronomer Henrietta Leavitt, cepheids, regularly varying pulsating stars, could be used as standard candle distance indicators. Identifying such a star allowed Hubble to show that Andromeda was not a small cluster of stars and gas within our own galaxy, but a large galaxy in its own right at a substantial distance from the Milky Way.
(Excerpt) Read more at 129.164.179.22 ...
[Credit: E. Hubble, NASA, ESA, R. Gendler, Z. Levay and the Hubble Heritage Team]
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Pretty amazing, and even though that slide is almost a century old, it really gives you a good idea how much these galaxies change over the years.
The distances involved are mind boggling.....
Not trying to burst a bubble here, but, almost all the changes are due to quality of the slide vs Hubble.
Galaxies don’t change much in a 1000 years, let alone 100.
Interesting photos as usual. It was the large picture of the Andromeda Galaxy that really opened my eyes to just how vast our universe is.
It sure looks like there are some fairly obvious changes in those two pictures to me...
Thank you, and happy July to you too.
Hubble was some guy, wasn’t he. If he were a young man today, imagine what he could do with all this high-rez, high-tech stuff.
It’s just that Hubble is that much better.
The originals were taken from ground based scope on a glass plate.
The new ones are taken from space based scope with a CCD camera. The length of exposure would also have an effect.
Your just seeing things better.
Galaxies change over a period of thousands if not millions of years. It takes 250 million years for the Milky Way to complete one revolution. 100 years is just a blink of the eye to a galaxy.
Hadn't occurred to me to think of "cepheids" as a keyword. LOL. That's the kind of sophisticated, erudite people we are here on FR.
Thanks Prospero!
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