Monday, January 8, 2018

100 Years Ago: Shapley Discovers True Magnitude of Milky Way & True Location of Earth in Galaxy

Photograph of astronomer Harlow Shapley, who discovered a century ago that the Milky Way Galaxy was much larger than previously thought, and that Earth and our Solar System are not at the center of the Galaxy. (Image Source: )
Near the end of this blog-post is a photograph showing Harlow Shapley at the ceremony, where he delivered the keynote address, for the dedication of a rather unique 10-inch Siderostat-Type Refractor Telescope at Pittsburgh's original Buhl Planetarium and Institute of Popular Science.

By Glenn A. Walsh
Reporting for SpaceWatchtower

As we move further into the 21st century, often people do not realize that it was only a century ago that we began to understand how large our Milky Way Galaxy really is, and our true place in the Galaxy.

Today, 100 years ago (on 1918 January 8), astronomer Harlow Shapley wrote a letter to British astronomer Arthur Eddington announcing a new breakthrough regarding the Universe's “galactic system.” In part, he wrote to Dr. Eddington:

To be brief, the globular clusters outline the sidereal system, but they avoid the plane of the Milky Way...All of our naked-eye stars, the irregular nebulae, eclipsing binaries—everything we know about, in fact, and call remote, [belong to this system] except those compactly formed globular clusters, a few outlying cluster-type variables, the Magellanic Clouds, and perhaps, the spiral nebulae. The globular clusters apparently can form and exist only in the parts of the universe where the star material is less dense and the gravitational forces less powerful than along the galactic plane. This view of the general system, I am afraid, will necessitate alterations in our ideas of star distribution and density in the galactic system.

Harlow Shapley studied bright globular star clusters, instead of individual stars. These globular clusters were outside of our Galaxy's true center, where cosmic dust blocks light from some stars (this cosmic dust had previously convinced astronomers that we were near the center of the Galaxy). The globular clusters studied were quite bright, even at large distances. After measuring the distances to many globular clusters, he was able to use them to find the true center of the Milky Way.

By observing and analyzing Cepheid and other variable stars, particularly RR Lyrae stars, he had concluded that the Milky Way Galaxy was much larger than astronomers of the time had believed. Now believing that our Galaxy was about 300,000 light-years in diameter, Dr. Shapley was correct that it was much larger than previously thought, but he also over-estimated the size..

And, while most scientists of the time assumed that our Solar System was in, or near, the center of the Milky Way Galaxy, Dr. Shapley also concluded, using parallax observations, that our Solar System was actually no-where near the center and actually toward one side of the Galaxy.

At the time Dr. Shapley was working for astronomer George Ellery Hale, using the 60-inch reflector telescope at Mount Wilson Observatory near Pasadena, California. The world's largest operating telescope at that time, the lens blank had been funded by Dr. Hale's father, William Hale, while the rest of the observatory was funded by industrialist and philanthropist Andrew Carnegie through his Carnegie Institution of Washington. Dr. Shapley went on to become Director of the Harvard College Observatory in 1921, remaining Director until 1952.

Harlow Shapley published a series of 14 scientific papers, between 1915 and 1919, detailing his research and conclusions. Scientists immediately read and started debating his results. Although American astronomer Henry Norris Russell wrote an article in Scientific American magazine, where he described Dr. Shapley's results as “simply amazing,” the general public did not become aware of the “great enlargement” of the Milky Way Galaxy until much later. Due to World War I and the War's aftermath, the first news article on the subject only appeared on the front page of The New York Times on 1921 May 31, along with a front page article in the Chicago Daily Tribune.

Although Harlow Shapley revolutionized our view of the Milky Way Galaxy, and the location of our Solar System in the Galaxy, his views were still very controversial among scientists, and he believed some things that have since been proven incorrect. While he had concluded that the Milky Way Galaxy was 300,000 light-years in diameter, we now know that our Galaxy is between 100,000 and 180,000 light-years in diameter.

Because he thought the Milky Way was so large, he also concluded that the Milky Way was most if not all of the Universe. For several scientific reasons, he thought that, what we know now as the Andromeda Galaxy as well as other spiral nebulae, could not be large and outside of our Galaxy.

Consequently, a Great Debate on the nature of the Universe and the possible existence of other galaxies was held between Dr. Shapley and Heber D. Curtis, Director of the Allegheny Observatory in Pittsburgh. This Great Debate was held before the U.S. National Academy of Sciences in Washington, DC on 1920 April 26.

Science author and retired college Astronomy professor Thomas William Hamilton writes, "What is generally overlooked, thanks to Shapley's own PR efforts, is that in the great debate between Harlow Shapley and Heber Curtis each was half right and half wrong, as Curtis persisted in the view we were near the center of our galaxy, but argued there are many other galaxies; while Shapley deduced we are on the outskirts, but believed ours was the only galaxy."

Although both astronomers presented convincing evidence for their positions (later, some of this evidence was verified by other scientists), regarding the main dispute of whether other galaxies existed, Dr. Curtis has been proven correct. (A link to additional information about this Great Debate near the end of this blog-post.)

Over the years, Harlow Shapley delivered many academic lectures. On Wednesday Evening, 1941 November 19, he delivered the keynote address at the dedication of a rather unique 10-inch Siderostat-Type Refractor Telescope at Pittsburgh's original Buhl Planetarium and Institute of Popular Science (a link to more information about this telescope near the end of this blog-post).

Harlow Shapley had a close relationship with Buhl Planetarium. Leo Scanlon, co-founder of the Amateur Astronomers Association of Pittsburgh in 1929, builder of the world's first all-aluminum observatory dome in 1930, and one of the first Buhl Planetarium lecturers in 1939, had worked with Dr. Shapley as early as 1934. After Mr. Scanlon presented a paper titled, "The Efficiency of Amateur Variable Star Observers," before the 1934 convention of the American Association of Variable Star Observers (AAVSO) at the Franklin Institute in Philadelphia, Dr. Shapley facetiously suggested that Mr. Scanlon should read the same paper to Dr. Shapley's sometimes sloppy staff at Harvard!

Harlow Shapley was a great supporter of Amateur Astronomy. Although delayed by the United States entry into World War II, a nation-wide organization of amateur astronomers, called the Astronomical League, was finally established on 1947 July 4. Dr. Shapley served as Interim President at the founding convention at Philadelphia's Franklin Institute (a preliminary planning meeting, in 1940, had occurred at Buhl Planetarium). (A link to additional information regarding the creation of the Astronomical League near the end of this blog-post.)

Harlow Shapley served on the Board of Trustees of Science Service from 1935 to 1971 and was elected President of the American Association for the Advancement of Science in 1947.

Today (2018 January 8) also marks the 150th anniversary of the birth of English astronomer Frank Watson Dyson, who became Director of the Royal Greenwich Observatory (England's Astronomer Royal) in 1910 and remained Director for 23 years. Dr. Dyson also studied the structure of the Milky Way and the Sun.

Frank Watson Dyson organized two historic expeditions to study the Total Eclipse of the Sun in 1919. He specifically proposed using observations from this eclipse to confirm predictions made by Albert Einstein, in Dr. Einstein's 1915 General Theory of Relativity. Observations of a slight shift in star positions near the Sun, during the eclipse, confirmed the theory's predictions, immediately making Albert Einstein world famous.

In the 1920s, Frank Watson Dyson started using the new technology of radio to transmit precise time signals of Greenwich Mean Time (the recognized international time scale used by most scientists, now known as Coordinated Universal Time) every quarter-hour on a radio station operated by the British Post Office. In 1924, he arranged for the British Broadcasting Corporation to transmit these precise time signals as “six pips” at the beginning of each hour. Back in 1868, Pittsburgh's Allegheny Observatory had provided railroads and cities precise time signals via the telegraph.

Special Thanks: Marilyn E. Morgan, Mount Wilson Observatory.

The following two news articles, with two photographs, come from the Pittsburgh Post-Gazette on Thursday Morning, 1941 November 20. The previous evening, Harvard College Observatory Director Harlow Shapley (third from left, in the left photograph) delivered the keynote address at the dedication of a rather unique 10-inch Siderostat-Type Refractor Telescope, at Pittsburgh's original Buhl Planetarium and Institute of Popular Science. Also pictured in this photograph are (left to right) William H. Barton, Director of New York City's Hayden Planetarium, Buhl Planetarium Director Arthur Draper, and Mrs. Nicholas E. Wagman (whose husband, at that time, was Director of Pittsburgh's Allegheny Observatory). (Sources: Pittsburgh Post-Gazette, Friends of the Zeiss)

Book Chapter Citation ---

Bartusiak, Marcia. The Day We Found the Universe. New York: Pantheon Books, 2009. 114-134. Print.

Internet Links to Additional Information ---

Harlow Shapley -
Link 1 >>>
Link 2 >>>

The 1920 Great Debate on the Scale of the Universe - Between Harlow Shapley and Heber D. Curtis, Director of Pittsburgh's Allegheny Observatory:
Link >>>

Harlow Shapley and Buhl Planetarium Assist in Creation of The Astronomical League:
Link >>>

10-inch Siderostat-Type Refractor Telescope at Pittsburgh's original Buhl Planetarium and Institute of Popular Science:
Link >>>

History of Andrew Carnegie and Carnegie Libraries:
Link >>>

Frank Watson Dyson ---

Related Blog Posts ---

"Centennial: Mt. Wilson Observatory's 100-inch Hooker Telescope." 2017 Nov. 3.

 Link >>>

Centennial: Einstein's General Theory of Relativity." 2015 Nov. 25.

Link >>>

Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss.
             2018 January 8.

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