by Ann » Fri Oct 06, 2023 6:23 am
This is indeed the perfect APOD for 6 October, 2023, exactly 100 years after Edwin Hubble "discovered the universe" (and proved that the Milky Way isn't "all there is").
Click to play embedded YouTube video.
Is that all there is?
It was Harlow Shapley that made Americans believe that "the Milky Way
is the Universe" after his
Great Debate with Heber Curtis. (Well, I'm sure I've read somewhere that smart Europeans had already figured out that those "island universes" are indeed galaxies of their own, but the Europeans let the Americans live on in their cosmic ignorance. Of course, I can't show you where I read it.
)
Anyway, Harlow Shapley was a really interesting character, in spite of his galactic misconceptions. He grew up on a farm in Missouri, only went to elementary school there, studied on his own at home and started working as a reporter - after having no more formal schooling than elementary school! - and later completed a six-year high school program in 1.5 years. Thereafter he went to university to study journalism, but
When he learned that the opening of the School of Journalism had been postponed for a year, he decided to study the first subject he came across in the course directory. Rejecting Archaeology, which Shapley later claimed he could not pronounce, he chose the next subject, Astronomy.
https://en.wikipedia.org/wiki/Harlow_Shapley
Shapley is famous for using the location of globular clusters to prove that the center of the Milky Way is in Sagittarius, and that the Milky Way is much larger than people had thought. (Well, it had to be large, if it was all there is!)
Shapley was able to (more or less) determine the distance to most globulars in the Milky Way thanks to the presence of variable stars, RR Lyrae stars, in the globulars. Henrietta Swan Leavitt had discovered another type of (brighter) variable stars, Cepheids, in the Small Magellanic Cloud, and she had showed that the period of variability of these stars is directly linked to the intrinsic luminosity of them.
SciHi Blog wrote:
On July 4, 1868, American astronomer Henrietta Swan Leavitt was born. She is best known for her discovery of the relation between the luminosity and the period of Cepheid variable stars. Based on her luminosity-period relation for Cepheids, Edwin Hubble was able to determine that the universe is expanding.
Actually Hubble used redshift and not Cepheids to show that the universe is expanding. But indeed, Hubble's first stepping stone came when he found one of "Henrietta's stars", a Cepheid, in the Andromeda Galaxy, and could show that Andromeda is well outside the limits of the Milky Way. (Well...
our halos are probably touching, but that's another matter.)
After Hubble had "
broken down the walls of the Milky Way" and shown the universe outside it, Shapley is said to have told a colleague, "Here is the letter (from Hubble) that destroyed my universe."
And today's APOD shows the triumphant discovery of a Cepheid in the Andromeda Galaxy! Well done, Edwin Hubble!
Ann
[img3="Edwin Hubble Discovers the Universe
Image Credit & Copyright: Courtesy Carnegie Institution for Science"]https://apod.nasa.gov/apod/image/2004/HubbleVarOrig_Carnegie_960.jpg[/img3]
This is indeed the perfect APOD for 6 October, 2023, exactly 100 years after Edwin Hubble "discovered the universe" (and proved that the Milky Way isn't "all there is").
[float=left][youtube]https://www.youtube.com/watch?v=LCRZZC-DH7M[/youtube][c][color=#0040FF]Is that all there is?[/color][/c][/float]
[clear][/clear]
It was Harlow Shapley that made Americans believe that "the Milky Way [b][i]is[/i][/b] the Universe" after his [url=https://en.wikipedia.org/wiki/Great_Debate_(astronomy)]Great Debate[/url] with Heber Curtis. (Well, I'm sure I've read somewhere that smart Europeans had already figured out that those "island universes" are indeed galaxies of their own, but the Europeans let the Americans live on in their cosmic ignorance. Of course, I can't show you where I read it. :wink: )
Anyway, Harlow Shapley was a really interesting character, in spite of his galactic misconceptions. He grew up on a farm in Missouri, only went to elementary school there, studied on his own at home and started working as a reporter - after having no more formal schooling than elementary school! - and later completed a six-year high school program in 1.5 years. Thereafter he went to university to study journalism, but
[quote]When he learned that the opening of the School of Journalism had been postponed for a year, he decided to study the first subject he came across in the course directory. Rejecting Archaeology, which Shapley later claimed he could not pronounce, he chose the next subject, Astronomy.
https://en.wikipedia.org/wiki/Harlow_Shapley[/quote]
Shapley is famous for using the location of globular clusters to prove that the center of the Milky Way is in Sagittarius, and that the Milky Way is much larger than people had thought. (Well, it had to be large, if it was all there is!)
[img3="Globular clusters of the Milky Way. Credit: Encyclopedia Britannica"]https://cdn.britannica.com/23/4423-050-964A0A08/Distribution-star-clusters-Galaxy.jpg[/img3]
Shapley was able to (more or less) determine the distance to most globulars in the Milky Way thanks to the presence of variable stars, RR Lyrae stars, in the globulars. Henrietta Swan Leavitt had discovered another type of (brighter) variable stars, Cepheids, in the Small Magellanic Cloud, and she had showed that the period of variability of these stars is directly linked to the intrinsic luminosity of them.
[float=left][img3="Henrietta Swan Leavitt."]https://cdn.britannica.com/66/158566-004-EBCD4212/Henrietta-Swan-Leavitt.jpg[/img3][/float][quote][url=http://scihi.org/henrietta-swan-leavitt-light-cepheids/]SciHi Blog[/url] wrote:
On July 4, 1868, American astronomer Henrietta Swan Leavitt was born. She is best known for her discovery of the relation between the luminosity and the period of Cepheid variable stars. Based on her luminosity-period relation for Cepheids, Edwin Hubble was able to determine that the universe is expanding.[/quote]
[clear][/clear]
Actually Hubble used redshift and not Cepheids to show that the universe is expanding. But indeed, Hubble's first stepping stone came when he found one of "Henrietta's stars", a Cepheid, in the Andromeda Galaxy, and could show that Andromeda is well outside the limits of the Milky Way. (Well... [url=https://www.space.com/andromeda-galaxy-halo-hubble-telescope-discovery.html]our halos are probably touching[/url], but that's another matter.)
[img3="Edwin Hubble at the controls of the 100-inch telescope at Mount Wilson, circa 1922. Soon he will discover a Cepheid in Andromeda."]https://i.redd.it/re7a4t7qftn01.jpg[/img3]
After Hubble had "[url=https://ras.ac.uk/sites/default/files/2018-09/1024px-Flammarion_Colored.jpg]broken down the walls of the Milky Way" and shown the universe outside it[/url], Shapley is said to have told a colleague, "Here is the letter (from Hubble) that destroyed my universe."
And today's APOD shows the triumphant discovery of a Cepheid in the Andromeda Galaxy! Well done, Edwin Hubble!
Ann