Harlow Shapley Project

 SHAPLEY’S KEY CONTRIBUTIONS TO SCIENCE

What can we learn about the Universe by peering far as we can into the night sky? What exactly is the Universe? And what is the Milky Way, the awesome dense white band across the night sky? For eons people have wondered about humanity’s place in the universe as they understood it.

In the early twentieth century a series of revolutionary answers was offered by a new generation of astronomers, telescopes and hard-to-believe physical theories. Harlow Shapley brought on the first of these revolutions, - displacing Copernicus’ model of a sun-centered universe that (dominated? reigned for 400 years.  

Between 1914 and 1918 Shapley discovered that our Milky Way galaxy is way bigger than believed. In a series of startling papers filled with tables and charts, Shapley mapped it is a flat wide disk. He showed the galactic center is a thick, dense bulge in the vicinity of the constellation Sagittarius in the southern hemisphere. He placed our solar system - Sun, earth, and us - two-thirds of the way out from the center.

    Our galaxy seen from afar looks like the Needle Galaxy, NGC 3545 shown above. VB from large font. The black-white image is from a 1935 lecture by J.S. Plaskett; it shows Shapley’s model after the diameter he proposed (300,000 light-years) was adjusted to 100,000 light-years, close to its present value.  233

    Copernicus and Galileo had already displaced the earth to a planet revolving around the sun. Now Shapley removed us to the sidelines of a “galactocentric” one. Or, as he often said in his Ozark farmer’s voice, “Man is not such a big chicken.”  

     A less known part of the story is how Shapley discovered the galaxy’s size and shape by mapping jewel like globular clusters.  His papers lay out interlocking steps for finding the distance to fainter objects based distances he found for nearer ones. Shapley was the first effectively apply Leavitt’s Law to measure the universe. 

Edwin Hubble started in the wake of Shapley’s revelations and used a more powerful telescope on Mount Wilson. Hubble relied on Shapley’s Cepheid-based ladder to search for Cepheids in the fuzzy nebulae and proved they are outside our galaxy - island universes. Hubble went on to show the expansion of the universe, measured on Shapley’s accepted distance scale.

Shapley made many other contributions in his long and restless scientific career.  In this list his mapping the galaxy and cosmic distance ladder are only Number I, The Cepheid Revolution. Four More Discoveries follow. Then three Breakthrough Contributions, assemblages of scientific knowledge with great impact. Any such list would be incomplete without Missed Discoveries. Missed Discoveries. The three here are often told by his critics; my review finds that failure in science can have surprising results. 

    The writeups are sketches by a non-science journalist and granddaughter who knew him well. This page can be a starting point for others’ work, debate and revisions. I am grateful to patient experts who have helped. The errors are mine alone.

CONTENTS

I  The Cepheid Revolution

I a Shapley's Ladder Across the Galaxy

I b Hubble Climbs Out to the Universe

I c A Generation of Astronomical Measurement

Shapley Quotes | About This List | Sources & Credits

I THE Cepheid Revolution

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But Shapley built a new ladder for measuring distances never attempted by astronomers. He based his ladder on some very bright Cepheid variable stars [that Henrietta Swan Leavitt discovered change] their apparent light periods according to distance: the period-luminosity or p-l Law.

Shapley made the first effective calibration of distance from earth to Leavitt’s Cepheids, which were in the Small Magellanic Cloud (SMC). Thus Shapley measured (and revised) this rung of his distance ladder.

His further work on Cepheids turned them into standard candles. Cepheids became rungs for probing more distant globular clusters. His 3-D map of 69 globular clusters, drawn in Fig 1, outlined a wide flat galaxy with a bulging center and the eccentric location of our Sun. 120 words

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A Rung 1 Cepheids
Placeholder Smith 70 & RA pp 4-5. Picked up HSL Law that observing the period in a Cepheid’s light variation he could determine it’s intrinsic brightness (luminosity) & hence it’s distance. Used Hz values for 11 close Cepheids to publish a distance to the Small Magellanic Cloud. (This is Paper II in 1915, recalib 1918 with a value …
This paper opened the door to detailed study and use of Cepheids as standard candles - which Shapley proceeded to do. (See I Ladder Across the Galaxy.) The 1914 paper opened the possibilities for Arthur S. Eddington, dean of British astronomers, to investigate how such pulsation occurs. Even Alan Sandage a later fierce critic of Shapley wrote that his “masterful” 1914 paper lon Cepheid pulsation ed to important work at Mount Wilson and a new field in astrophysics.

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ILLUS B Why many accounts focus on how he was wrong (too big?) no dust, etc. But it was accepted & corroborated (landmark & oort) even as crit of basing a rev’y model on 11 Cepheids seemed a reach.

Shapley went to havarrd. Contiued to defend an ultimately wrong position that Big galaxy holds sp neb.

Placeholder Smith 70 & RA pp 4-5. Picked up HSL Law that observing the period in a Cepheid’s light variation he could determine it’s intrinsic brightness (luminosity) & hence it’s distance. Used Hz values for 11 close Cepheids to publish a distance to the Small Magellanic Cloud. (This is Paper II in 1915, recalib 1918 with a value …

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B Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum justo purus, sodales quis tincidunt sed, tristique id purus. Proin diam risus, iaculis sit amet arcu eget, aliquet convallis diam. Duis ac nulla justo. Etiam euismod tincidunt auctor. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum justo purus, sodales quis tincidunt sed, tristique id purus. Proin diam risus, iaculis sit amet arcu eget, aliquet convallis diam. Duis ac nulla justo. Etiam euismod tincidunt auctor.

C Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum justo purus, sodales quis tincidunt sed, tristique id purus. Proin diam risus, iaculis sit amet arcu eget, aliquet convallis diam. Duis ac nulla justo. Etiam euismod tincidunt auctor. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum justo purus, sodales quis tincidunt sed, tristique id purus. Proin diam risus, iaculis sit amet arcu eget, aliquet convallis diam. Duis ac nulla justo. Etiam euismod tincidunt auctor.

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BOX Blue Rim (for quotes from hubble) Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum justo purus, sodales quis tincidunt sed, tristique id purus. Proin diam risus, iaculis sit amet arcu eget, aliquet convallis diam. Duis ac nulla justo. Etiam euismod tincidunt auctor. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum justo purus, sodales quis tincidunt sed, tristique id purus. Proin diam risus, iaculis sit amet arcu eget, aliquet convallis diam. Duis ac nulla justo. Etiam euismod tincidunt auctor.

F Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum justo purus, sodales quis tincidunt sed, tristique id purus. Proin diam risus, iaculis sit amet arcu eget, aliquet convallis diam. Duis ac nulla justo. Etiam euismod tincidunt auctor. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum justo purus, sodales quis tincidunt sed, tristique id purus. Proin diam risus, iaculis sit amet arcu eget, aliquet convallis diam. Duis ac nulla justo. Etiam euismod tincidunt auctor.

G Slipher + Speed Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum justo purus, sodales quis tincidunt sed, tristique id purus. Proin diam risus, iaculis sit amet arcu eget, aliquet convallis diam. Duis ac nulla justo. Etiam euismod tincidunt auctor. Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum justo purus, sodales quis tincidunt sed, tristique id purus. Proin diam risus, iaculis sit amet arcu eget, aliquet convallis diam. Duis ac nulla justo. Etiam euismod tincidunt auctor.

“ I have always admired the way in which Shapley finished the whole problem in a very short time, ending up with a picture of the Galaxy that just about smashed up all the old school’s ideas about galactic dimensions.”
—Walter Baade, quoted in OG HS and MWO p.16

Extra Text Box: Again, I was not sure if you wanted a text box between the box with blue rin and the slide image below so inserting here for good measure. We can delete if this box is superfluous.
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Marker: Sophia has worked until this section. Below this note, I have not worked on anything during our Dec 19th session. Everything you see below is from our earlier work together.

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SO - Remember we have a link to Shapley Quotes which run at the bottom of this page. It is useful to keep this one even in the top only version to be released first. Your choice how to format. Open accordion style? Ds 1-2-2024

Moment of Discovery of the galaxy’s true shape in 1918

”It was a shocking thought--this sudden realization that the center of the universe was not where we stood but far off in space, that our heliocentric picture of the universe must be replaced by a strange sort of eccentric universe.

    “Gradually a reorienting view developed; “I have put it wrong end to. I should not say or think that the center of our universe is so remote and removed from us, so removed from the proud observers.

“No, I should say that the trivial observer is far from the magnificent, star-filled center! He is the peripheral, the ephemeral one. He is the incidental biological by-product of water, soil, air and sunlight. He is off in a cosmic corner, invisible from the central nucleus around which billions of stars revolve and to which we, like they, pay gravitational homage.”

— View from a Distant Star, 1964, p. 2 Q# 1  HS Quotes VDS started 12-7-24.docx

II. MORE DISCOVERIES

But Shapley, the expert on binaries, argued that Cepheids cannot be doubles. If they were their [mass] the envelopes of the giant stars would overlap] HHS will check would make them fall into each other. So their periodic, regular changes of light must be due to internal pulsation. These can be traced by their color and temperature changes through each cycle.

     Shapley’s August 1914 paper is less famous than some of his other work. Yet it led to close definition of Cepheid spectral type changes. Shapley and Walter Adams showed spectral variations in Delta Cephei itself. They reported changes for 8 more Cepheids in 1916. One of Martha Shapley’s papers with her husband showed the varying shape of the light curve of  XX Cygni.  RR Lyraes were investigated for their spectral changes.

        This paper opened the door to detailed study and use of Cepheids as standard candles which Shapley proceeded to do. I. Ladder Across the Galaxy. It opened the way for the dean of British astronomers Arthur S. Eddington to ask how such pulsation occurs - a new branch of astrophysics.

      Though the 1914 paper was a brief, more than a discovery,  it “changed the way astronomers thought of Cepheids,” says astronomer and historian Horace Smith.  258

    The stars and globular clusters in our galaxy’s stellar Corona or Halo tend to be old, astronomers found. They are Population II stars in Walter Baade’s classification in the late 1940s. IV c. Missed Discoveries: Two Populations. We now know our galaxy is also enveloped in a “galactic corona” of gaseous material. Our third is the mysterious Dark Matter Corona, or Halo.

  In 2022 two Harvard astronomers released a study of the stellar halo showing it is a bit sausage-shaped, not a simple sphere. "The stellar halo is a dynamic tracer of the galactic halo," said Jiwon “Jesse” Han, a coauthor on the study. She and (title) Charlie Conroy said its odd shape could be from a long-ago collision and “help the quest for the dark matter halo.”

   Thus today’s work on dark matter is informed by studying our galaxy’s stellar corona which Shapley defined back in 1939.

   He wrote that this feature appears on “two plates taken with a patrol camera” by Solon Bailey in 1909! “The hazy extension was first uncertainly seen on one of his small-scale plates that had a total exposure of 23.4 hours, distributed over four good nights.” The star counts had been confirmed with the Bruce telescope. Harvard’s 60-inch reflector at South Africa station “is probing the star counts.”

    The feature is much wider and larger than seen before; it covers so much of the distance between the Small and Large clouds “we can more assuredly than ever say they these neighboring irregular galaxies are part of a pair.”

III Breakthrough COntributions

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IV. Discoveries Missed

So there is no white dwarf branch on the diagram of evolution Russell published in 1914. ILLUS The name only was given in 1922.

They were dwarfs the size of earth yet with mass maybe 25,000 times our sun’s mass.  The dean of British astronomers Arthur Eddington wrote white dwarfs seemed “impossible.”

more text

Shapley had discovered the white dwarf galaxies Sculptor and Fornax in 1937 and 1938. II. Other Discoveries: Sculptor and Fornax. From 1939 in California on Mount Wilson, Walter Baade and Edwin Hubble studied these new strange objects with the 100-inch telescope, though they were low on the southern horizon and visible only a few hours a night.

Ironically the breakout of war enabled Baade to make his greatest discovery. The city lights of Los Angeles were turned down; the dark skies improved telescope viewing from Mount Wilson to the north. As a German national Baade was confined to stay there while Hubble and other colleagues left to serve.

   In better-known galaxies like Andromeda Baade noticed the distribution of younger stars (blue giants) in some parts and lack of them in globular clusters of our galaxy’s halo. (II Other Discoveries: Corona) Comparing M 31, M 32 and 25 “and switching back and forth to Sculptor and Fornax,” (DO97-98) Baade tallied supergiants, younger, brighter stars in central regions of some galaxies, but not in the globular clusters. In 1943 he proposed these including RR Lyrae a general older class: Population II. He published his case for two populations in 1944 papers and an AAS presentation in Ohio in 1947.

    The result is that Cepheids Hubble had found in Andromeda were fainter inherently.  Hubble had plotted magnitudes and distances of Cepheids in the Magellanic Clouds (and near to us) and those in gcs (galactic) because Shapley’s basic curve plotted them as one.. As for the Cepheids in M31 Andromeda, which Hubble identified as TKs distance based on Shapley’s curve, Baade said they could be inherently fainter, Population II stars, and actually farther away. Another key result. If Andromeda was farther away, it would be comparable in size to our galaxy, and only appear smaller to ours. 

     Shapley “would not hear” of Baade’s suggestion that his original period-luminosity curve should be dissected, because it could have blended two populations of Cepheids with misleading results. Shapley, Baade wrote, treated the Magellanic Clouds <as his personal property.> In effect only Harvard’s southern telescopes could study them thoroughly and he, Virginia McKibben Nail and Bart Bok were the experts!

   Shapley did send Baade one key result: no RR Lyrae stars could be seen in the clouds. This suggested they and their Cepheids were young. Simultaneously a South African astronomer David Andrew Thackeray, encouraged by Baade, had dived into the clouds and independently discerned young and old populations. Thackeray would report this at the IAU in Rome in 1952; he stood up spontaneously during Baade’s definitive lecture and confirmed there are two classes of Cepheids.

Shapley was present at the Rome session when Baade revealed this conclusion. Shapley did himself no favors when he]submitted an article to Science Service about the discovery, declaring he had made it! The ‘news’ ran in The New York Times January 5, 1953. Baade was understandably furious. At Harvard, the piece was quietly withdrawn. 

His appalling act cemented dislike for Shapley by “West Coast” astronomers and his critics at Harvard. There the changing of the guard was under way. Shapley was due to retire after 32 years as director on December 31, 1952. Observatory management was already by a committee J. Robert Oppenheimer chaired at President James B. Conant’s request. The Harvard trustees had told Shapley he would not get the life title of university professor. Senator Joseph McCarthy was after him. At least Martha had been reinstated in her security job at MIT.

    In any event, the episode shows again that scientists at some junctures are too emotional to live up to their profession’s ideals. 

Owen Gingerich, whom Shapley hired as a graduate student in 195_ and was with him throughout this time, told me that Shapley was shaken by Baade’s beating him to the discovery of young and old Cepheids and recalibration of the universe and our galaxy’s size in relation to it. Gingerich said, as I recall:

  “Shapley had been hunting for a second great discovery in the Magellanic Clouds. He had missed it, through it had been right in front of him all along. It was his King Lear moment.”

His appointment as Paine Professor ran through 1956. Shapley went on publishing Magellanic Clouds studies with Nail and others. In the 1952-53 time of personal strain he invented and taught his novel course on cosmogony; this bundle of ideas gave rise to his years of speaking and writing on cosmic evolution. Shapley would influence astronomers and some in the public to conclude with him, in 1953, “we are not alone.” III Breakthrough Initiatives: Cosmic Evolution.

In sum, the size of the universe and new distance rods were made by Baade’s discovery there two populations of star. They include two types of Cepheids: older W. Virginis type in globular clusters, Fornax, Sculptor and Andromeda and the inherently brighter Classical Cepheids in the Magellanic Clouds and elsewhere.

Could Shapley have done this? In his essay “Shapley’s Impact, Owen Gingerich wrote that Baade had access to much better telescope and was a focused extraordinary observer.

“Did Shapley lose out by abandoning the giant telescopes of the West? Probably not - for, as I have noted, few have the chance to make even one discovery as grand - and few have the chance to build astronomy through education, activism, and public appeal.”

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