Harlow Shapley concluded that the Sun was not in the center of the Milky Way Galaxy by

Laurence A. Marschall in the department of physics at Gettysburg College in Gettysburg, Pa., answers:

"There is no short answer to this question, because astronomers have followed many lines of evidence to determine the location of the solar system in the Milky Way. But some of the general techniques can be outlined briefly.

"Finding one's location in a cloud of a hundred billion stars--when one can't travel beyond one's own planet--is like trying to map out the shape of a forest while tied to one of the trees. One gets a rough idea of the shape of the Milky Way galaxy by just looking around--a ragged, hazy band of light circles the sky. It is about 15 degrees wide, and stars are concentrated fairly evenly along the strip. That observation indicates that our Milky Way Galaxy is a flattened disk of stars, with us located somewhere near the plane of the disk. Were it not a flattened disk, it would look different. For instance, if it were a sphere of stars, we would see its glow all over the sky, not just in a narrow band. And if we were above or below the disk plane by a substantial amount, we would not see it split the sky in half--the glow of the Milky Way would be brighter on one side of the sky than on the other.

"The position of the sun in the Milky Way can be further pinned down by measuring the distance to all the stars we can see. In the late 18th century, astronomer William Herschel tried to do this, concluding that the earth was in the center of a 'grindstone'-shaped cloud of stars. But Herschel was not aware of the presence of small particles of interstellar dust, which obscure the light from the most distant stars in the Milky Way. We appeared to be in the center of the cloud because we could see no further in all directions. To a person tied to a tree in a foggy forest, it looks like the forest stretches equally away in all directions, wherever one is.

"A major breakthrough in moving the earth from the center of the galaxy to a point about 3/5 away from the edge came in the early decades of this century, when Harlow Shapley measured the distance to the large clusters of stars called globular clusters. He found they were distributed in a spherical distribution about 100,000 light-years in diameter, centered on a location in the constellation Sagittarius. Shapley concluded (and other astronomers have since verified) that the center of the distribution of globular clusters is the center of the Milky Way as well, so our galaxy looks like a flat disk of stars embedded in a spherical cloud, or 'halo,' of globular clusters.

"In the past 75 years, astronomers have refined this picture, using a variety of techniques of radio, optical, infrared and even x-ray astronomy, to fill in the details: the location of spiral arms, clouds of gas and dust, concentrations of moleculesand so on. The essential modern picture is that our solar system is located on the inner edge of a spiral arm, about 25,000 light-years from the center of the galaxy, which is in the direction of the constellation of Sagittarius.

"For details on how we know all this, there are, fortunately, two excellent and complementary books: The Discovery of Our Galaxy, by Charles A. Whitney (Knopf, 1971), and The Alchemy of the Heavens: Searching for Meaning in the Milky Way , by Ken Croswell (Anchor Books, 1995).

Since the clusters assumed a spherical arrangement, it was logical to conclude that they would cluster around the centre of the Galaxy; from this conclusion and his other distance data Shapley deduced that the Sun lies at a distance of about 50,000 light-years from the centre of the Galaxy; the number was later …

How did Harlow Shapley deduce the location of the center of the Milky Way galaxy?

Harlow Shapley analysed the locations of globular clusters, finding them to be centred around a point somewhere in Sagittarius. He deduced that this was probably the location of the centre of the galaxy. … With the data at his disposal, he estimated the distance to the centre of the galaxy as approximately 15 kpc.

How did Harlow Shapley conclude that the sun was not in the center of the Milky Way galaxy?

Shapley used the distribution of globular clusters in the galaxy to determine that the Sun was not at the center of the Milky Way.

What observations led Harlow Shapley to conclude that we are not at the center of the galaxy?

What observations led Harlow Shapley to conclude that we are not at the center of the Galaxy? Shapley noted that most globular clusters were in just a few contellations around Sagittarius.

How do we know the Sun is not at the center of the Milky Way?

How do we know that the sun is not at the center of the Milky Way? The distribution of globular clusters shows the Sun is not at the center of the Milky Way. The Herschels attemped to etermine the galaxy’s structure by: systematically counting stars in each direction.

What was Harlow Shapley wrong about?

He is also known to have incorrectly opposed Edwin Hubble’s observations that there are additional galaxies in the universe other than the Milky Way. Shapley fiercely critiqued Hubble and regarded his work as junk science.

Can we see the center of our Galaxy?

Dust and gas are necessary to form stars, and most stars are formed within the spiral arms. Note that we can’t really see the center of the galaxy with our eyes because there is dust in the way! … The Galactic Center is unfortunately hidden by dark dust in visible light!

What kind of object do we think lies in the center of the Milky Way galaxy?

The Galactic Center (or Galactic Centre) is the rotational center, the barycenter, of the Milky Way galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which powers the compact radio source Sagittarius A*, which is almost exactly at the galactic rotational center.

What is the evidence for dark matter in our Galaxy?

Primary evidence for dark matter comes from calculations showing that many galaxies would fly apart, or that they would not have formed or would not move as they do, if they did not contain a large amount of unseen matter.

How do we know the Milky Way is a barred spiral galaxy?

The clues we have to the shape of the Milky Way are: 1) When you look toward the Galactic Center

Is the sun located in the center of the Milky Way?

Bottom line: The sun is about 1/3 the distance from the center of the Milky Way galaxy to its outer edges. It’s located in a smaller spiral arm, between two large arms, called the Orion Arm.

Is the sun at the Centre of the Milky Way?

The Sun does not lie near the center of our Galaxy. It lies about 8 kpc from the center on what is known as the Orion Arm of the Milky Way.

Why is the solar system not in the center of the Milky Way?

Hubble discovered that the galaxies are moving away from us with a velocity proportional to their distance. Every point in the universe is expanding from every other point at a constant rate. There is no expansion from a particular point. … Since the universe has no edge – it is unbound – it has no centre.

What explains the Milky Way’s spiral arms?

Spiral arms remove angular momentum from the center of the galaxy, allowing it to achieve a state of higher binding energy. There are two main versions of the theory of spiraling: one in which the waves are steady and long-lived, the other in which spirals are transient features that come and go.

What did Shapley not know messed up his measurements?

Shapley, the prodigy, made a monumentally correct deduction from existing astronomical data that our Sun was not at the center of our Galaxy and that our Galaxy was much larger than anyone had previously believed.

Why do galactic disks appear blue?

Harlow Shapley found the Milky Way was: much larger than previously thought. Galactic disks appear blue because: … They believed that the Milky Way was the entire universe.

"Theories crumble, but good observations never fade." - Harlow Shapley

Early in his life, Harlow Shapley resolved to educate himself. Years later, as the director of the Harvard College Observatory, Shapley made education of the public an integral part of the Observatory's mission.

How did Harlow Shapley become interested in the stars, and what was the work he did with Cepheid variable stars and globular clusters? What important discoveries did Shapley make about the Milky Way galaxy?

Early Education

Harlow Shapley was born in Nashville, Missouri, on November 2, 1885. A twin, both Harlow and his brother Horace were named after their grandfathers. Shapley's father was a successful hay producer and dealer, and his childhood was spent on the family farm; he received much of his early education in a one-room schoolhouse. At the age of 16, Harlow took a course at a business school and became a newspaper reporter and city editor for the Daily Sun in Chanute, Kansas. He decided to save his money and pursue higher education. After attending the Carthage Collegiate Institute in Missouri, Shapley graduated as valedictorian of his class.

Astronomy

Shapley next entered the University of Missouri at Columbia, intent on studying journalism. After discovering that the journalism department wasn't yet open, Shapley took up astronomy instead (later, Shapley would say that he had opened an alphabetical catalog of courses, found himself unable to pronounce archaeology, and so went on to astronomy). Astronomer Frederick Hanley Seares first sparked in him an interest in the study of stars. He earned his bachelor's degree in 1910 and his master's degree one year later.

Fellowship

Shapley was awarded the Thaw fellowship of Princeton University and began studying as a doctoral candidate under Henry Norris Russell, who was the head of the astronomy department there. Russell's work involved using stellar spectra to determine the properties of stars and the orbits of spectroscopic binary, or double stars. By 1913, Shapley had earned his Ph.D. His dissertation was entitled, "The Orbits of Eighty-Seven Eclipsing Binaries - a Summary." Shapley's thesis was a valuable contribution to the field of astronomy; it dealt with methods for determining the physical properties of eclipsing binary stars. Shapley became interested in determining the distances to these stars.

Mount Wilson

After traveling to Europe where he met many European astronomers, Shapley made a stop in Kansas City to marry his wife, Martha Betz Shapley, in April 1914. The same year, Harlow was offered and accepted a position at Mount Wilson Observatory in California. Martha assisted her husband in astronomical research at Mount Wilson and later at the Harvard College Observatory. She authored and co-authored numerous articles on eclipsing stars and other astronomical objects. Harlow and Martha had five children together, four sons and one daughter.

Cepheids

At Mount Wilson, Shapley studied Cepheid variable stars, using them as indicators of the distances of globular clusters—compact, spherical collections of stars. Within a year, Shapley realized that the Cepheid variable stars are not eclipsing binaries, but rather single pulsating stars. In other words, the Cepheids are single stars that periodically expand and contract with an accompanying change in luminosity. Their distances could then be determined by measuring their apparent magnitudes, using Henrietta S. Leavitt's 1912 period-luminosity relationship to obtain their average brightness or average "absolute magnitude." And, since pulsating Cepheid stars frequently occur in globular clusters, Shapley could use the former to determine distances to the latter. His greatest contribution to science came of this work; in 1918, Shapley developed a new picture of the shape and size of the galaxy.

The Great Debate

In April of 1920, Shapley participated in the Shapley-Curtis Debate in Washington, D.C. This "Great Debate" saw Shapley and Herber D. Curtis arguing over the scale of the universe, as well as the nature of nebulas and galaxies. Curtis argued that the universe is made up of many galaxies similar to ours (these had been identified by astronomers of the time as "spiral nebulae.") Shapley argued that spiral nebulae were clouds of gas and that they and globular clusters occur within the Milky Way galaxy. Shapley was against Curtis' position that the Sun was at the center of the galaxy, saying that our solar system exists in the outer limits of a very large galaxy. He was correct on this point, although Edwin Hubble helped prove Shapley's position about nebulae and globular clusters occurring within our galaxy wrong when he demonstrated that the Cepheid variables in the Andromeda galaxy were much further away than Shapley's proposed extent of the Milky Way and that Andromeda was indeed its own "island universe."

Harvard

In 1921, Harlow Shapley became the director of the Harvard College Observatory to replace the deceased Edward Charles Pickering. Under his leadership, it became one of the world's most important centers for astronomy training and research. Shapley established the graduate school of astronomy as part of the educational structure of Harvard University. He was also responsible for mandating that public education be made a part of the Observatory's mission; a requirement for students in the Harvard program was lectures and presentations for school children. Shapley remained as the Observatory's director until 1952, and then continued research as the Paine Professor of Practical Astronomy until his retirement in 1956. After that, he continued his work as both a lecturer and an author.

In the Interest of Science

During his time at the Harvard Observatory, Shapley was involved in many scientific societies, including the American Astronomical Society, the American Association for the Advancement of Science, and Sigma Xi. He also served on the committees that helped found the National Science Foundation and UNESCO (United Nations Educational, Scientific and Cultural Organization). A member of numerous academies and the recipient of many prestigious prizes, Harlow Shapley did much to help popularize the field of astronomy. He was active in the professional as well as political interests of science.

Shapley was a political liberal and became a victim of McCarthyism. Joseph McCarthy claimed that Shapley was a communist in the State Department, even though Shapley had no real connection to it. Shapley responded to the press saying, "the Senator succeeded in telling six lies in four sentences, which is probably the indoor record for mendacity." Shapley was, however, a friend of Henry A. Wallace and attended the Progressive Party convention in 1948. He supported Wallace on a personal level, but was against the pro-Soviet positions of the Progressive Party.

Next to astronomy, Shapley's greatest interest was myrmecology, the study of ants. He spent much time studying them in the daylight hours at Mount Wilson, and even published a few papers on ant behavior.

Harlow Shapley died on October 20, 1972—just shy of his 87th birthday—in Boulder, Colorado, during a visit to his son.

Determining Distance

Harlow Shapley was the first to realize that the Milky Way Galaxy was much larger than previously believed. Using the 60-inch telescope at Mount Wilson, he took photographs and observed globular clusters, which were compact spheres composed of many thousands of stars. Shapley used Henrietta Swan Leavitt's method for Cepheid variable stars to determine distances to globular clusters.

In 1912, American astronomer Henrietta Leavitt used the degree of brightness of Cepheid stars, whose brightness vary at regular intervals, in the Magellanic Clouds to measure their distance from the Earth. The longer the time a Cepheid star takes to undergo a complete cycle, the higher the star's average brightness or average "absolute magnitude". Leavitt was able to determine the distance from Earth to the nebula by comparing the brightness of the star as seen from Earth with the star's actual brightness, which was estimated using the length of the star's cycle.

Big Galaxy

Shapley discovered variable stars in a large percentage of the globular clusters he observed. He used Leavitt's method that relied on Cepheid brightness to determine the distances to all of the clusters he observed. The estimated distances to the globular clusters were very large, ranging from 50,000 to 220,000 light years away. He published his "Big Galaxy" theory in 1918, which proposed his calculated diameter of the galaxy at 300,000 light years. Like a majority of astronomers at that time, Shapley thought the Milky Way galaxy made up the entire universe.

Calculating Center

Through his study of the distribution of globular clusters in the Milky Way, Shapley calculated that our Sun, previously thought to lie near the center of the galaxy, was 50,000 light years from the center of the Milky Way. This resulted in the first realistic assessment of the size of our galaxy (scientists now know that this number is approximately 26,000 light years). Shapley correctly determined the galactic center of the Milky Way to be located in the constellation of Sagittarius. He did this by mapping out a three-dimensional distribution of the globular clusters.

As a result of Shapley's work, scientists began to have a better understanding of the Milky Way, a galaxy far larger than generally believed at that time.

Acknowledgement

Harlow Shapley was awarded the 1945 Franklin Medal in Physics for "Contributions to Astronomy; measurement of galaxies of vast distances necessary for the determination of the nature and extent of our galaxy and others."

Numerous other awards and honors were bestowed on Shapley and he held many positions of importance. Some of these include:

- 1926 Draper Medal, National Academy of Sciences - 1926 University Medal, Brussels - 1931 Medal, Society of Arts and Sciences - 1933 Rumford Medal, American Academy of Arts and Sciences - 1934 Gold Medal, Royal Astronomical Society - Janssen Prix of the Astronomical Society, France - 1939 Bruce Medal, Astronomical Society of the Pacific - Pope Pius XI Prize - President of American Academy of Arts and Sciences, 1939-1944 - President of American Association for the Advancement of Science, 1947

- President of Sigma Xi, The Scientific Research Society of North America, 1943-1947

Named for Harlow Shapley: The Shapley crater on the moon, Asteroid 1123 Shapleya, and the American Astronomical Association's Harlow Shapley Visiting Lectureships in Astronomy.

The Harlow Shapley presentation was made possible by support from The Barra Foundation and Unisys.