Henry Norris Russell

Astronomer

• Born: October 25, 1877
• Birthplace: Oyster Bay, New York
• Died: February 18, 1957
• Place of death: Princeton, New Jersey

American astrophysicist

Henry Norris Russell was among the first astrophysical theorists in the United States. Seeking to explain his observations and to understand the physics of stars, he incorporated theory into the descriptive science of astronomy. He is best known for his work in developing the Hertzsprung-Russell (H-R) diagram, a major tool used to understand the composition and evolution of stars.

Born: October 25, 1877; Oyster Bay, New York

Died: February 18, 1957; Princeton, New Jersey

Primary fields: Astronomy; physics

Specialties: Astrophysics; theoretical astronomy

Early Life

Henry Norris Russell was born the first son of Presbyterian pastor Alexander Gatherer Russell and Eliza Hoxie Norris Russell, in Oyster Bay, New York. Raised in a strict Christian home, Russell was profoundly affected by his religious upbringing and remained deeply faithful his entire life. In 1890, Russell entered the Princeton Preparatory School and stayed with his maternal aunt, Ada Louise Norris, in Princeton, New Jersey, during the school year. He would return to Oyster Bay during the summer months. Russell proved to be an excellent student.

In 1893, just one month before his sixteenth birthday, Russell entered the College of New Jersey (now Princeton University). In 1897, he graduated with highest honors. He continued his studies and received his PhD in 1900. His doctoral work led to the development of methods to study binary star orbits. However, health problems forced Russell to interrupt his work for the rest of that year.

By 1902, Russell had traveled to Cambridge University in England to study and do research. He returned to Princeton in 1905 to accept a faculty position, living again with his aunt Ada. He soon met Lucy May Cole, and they were married on November 24, 1908. The couple, who lived with Ada, would have three daughters and a son. Ada died in 1914, leaving her home to her nephew, and he lived there for most of the rest of his life.

Life’s Work

Throughout his career, Russell worked on a wide range of areas in astronomy, studying geophysics, the stars, planets, nebulas, and the moon. He did not study much of the galaxies, however. Russell’s earliest work on binary stars provided new ways to compute parallaxes, which are important in determining stellar distances. His studies of eclipsing binary stars allowed him to determine the sizes of stars, and he determined new ways to estimate the masses of binary star systems. His work, always careful and painstakingly accurate, set a new standard of precision for researchers.

Russell discovered several critical important relationships among stars. By knowing the distances of stars and their apparent magnitudes (how bright the stars appear in the sky), he could determine the absolute magnitudes of stars (how luminous a star is in actuality). He observed a definite pattern between the luminosity of a star and its color. The color of a star is related to its temperature, and almost all of the very hot, blue stars are also very bright. However, only some of the cool, red stars are bright as well. Most of the cooler stars are dim. This observation led him to propose that cool stars could be separated into two groups. Those in the brighter group, he reasoned, must also be much larger than the dimmer group.

Unknown to Russell, Danish astronomer Ejnar Hertzsprung had been working on very similar studies. When Russell was told of Hertzsprung’s studies, he immediately embraced Hertzsprung’s work and even adopted his terms “giant” and “dwarf” for these two groups of stars. Most of this data was in tabular form until Russell produced a plot of absolute magnitudes versus spectral types in 1913. This plot was presented at meetings of the Royal Astronomical Society and the American Astronomical Society. Astronomers immediately recognized how such a graphical representation of the data could be used to understand stars better. American astronomers began to refer to the plot as the Russell diagram, but by the 1930s, astronomers worldwide began to call it the Hertzsprung-Russell (H-R) diagram, noting Hertzsprung’s contributions as well.

In his quest to understand stars, Russell spent much of his career working on a theory of stellar evolution. He observed that most stars appear to lie along a strip that runs diagonally across the absolute magnitude versus spectral type plot from the upper left to the lower right. However, some stars seem to lie along a strip leading from the upper left to the upper right on the diagram; this strip became known as the main sequence. The stars in the upper right of the strip, Russell reasoned, are Hertzsprung’s giant stars, while stars on the main sequence are dwarf stars. Russell eventually settled upon a model in which stars begin as giants and then become smaller and hotter until they appear on the upper-left portion of the main sequence. Then, he hypothesized that the stars move down along the main sequence, becoming cooler and dimmer.

Though many aspects of this model turned out to be incorrect, astronomers have found that stars do indeed begin in the upper right of the H-R diagram and move onto the main sequence. However, they do not move along the main sequence. Rather, when they begin to die, they again move off the main sequence to the upper right portion of the diagram.

Eager to help in the war effort during World War I, Russell became affiliated with George Ellery Hale’s National Research Council. He initially worked on a project to improve artillery parallax and ranging. Later, he worked on aircraft navigation systems. After the war, he returned to his job as a Princeton professor.

To determine the chemical composition of stars, Russell worked with stellar spectroscopy. Like most astronomers of his day, he believed that the sun and stars are composed of materials similar to those that compose the Earth. Because different stars showed different spectral lines, Russell believed they had different compositions. However, Cecilia Payne, in doing research for her PhD, concluded that the sun and all stars essentially have the same composition, almost entirely hydrogen and helium, which turned out to be a controversial finding. Russell strongly disagreed with Payne’s theory because those elements are very rare on Earth. Under his influence, Payne backed down from her theory and even declared her work flawed. However, when Russell, who was more interested in truth than in being right, was presented later with undeniable evidence that Payne’s conclusions were correct, he became a wholehearted supporter of her theory that stars were composed mostly of hydrogen and helium.

Impact

Russell’s most enduring legacy was his work in determining relationships between the luminosity and temperature of stars. His plot of absolute magnitude versus spectral type became the basis of all future graphical depictions diagramming that data. The H-R diagram was critical to the development of a theory of stellar evolution and has become one of the most important and useful tools for stellar astronomers.

Russell also was instrumental in bringing theoretical physics into astronomy. Until his time, astronomy, particularly in the Americas, amounted to cataloging and describing what one observed through research. Russell, however, sought to explain observations and to understand the physics of stars.

In addition to his professional contributions, Russell brought astronomy to those outside the field. He wrote a monthly column for Scientific American magazine and eventually became an associate editor of astronomy for the magazine. In addition, he coauthored a textbook, lectured to students, and gave several public talks on the topic of science and religion. Finally, Russell was one of the last astronomers to work as a generalist in the field, focusing his work on a wide range of topics. Later astronomers would tend to become specialists in certain subfields of astronomy.

Bibliography

DeVorkin, David H. Henry Norris Russell: Dean of American Astronomers. Princeton: Princeton UP, 2000. Print. A well-researched and thorough biography of Henry Norris Russell. Includes an extensive bibliography.

Gregersen, Erik, ed. “Henry Norris Russell.” The Universe: A Historical Survey of Beliefs, Theories, and Laws. New York: Britannica Educational, 2010. 78–82. Print. Contains a brief biography of Russell, focusing primarily on the development of his most lasting legacy, the Hertzsprung-Russell diagram.

Talcott, Richard. “Making Sense of Stars.” Astronomy 34.4 (2006): 53–56. Print. A very short and easy to understand explanation of the Hertzsprung-Russell diagram and how it is used. Includes diagram examples.