Until the early 19th century, astronomers could do little more than watch the night sky and the movements of the stars charting. But astrophysics brought many new opportunities. The American Henry Norris Russell was one of the first astrophysicists he suggested a color-luminosity diagram for research into the life of stars. This so-called HR diagram is still a resource for astronomers.
Astrophysics: A new direction in astronomy
Astrophysics, the study of the composition and evolution of the stars, was made possible by spectroscopy: 19th-century scientists knew was that white light colors and you could assign it to this spectrum (range of consecutive colors) became visible light. In 1814 the German physicist Joseph von Fraunhofer split light from the sun and discovered that there were in the color bands to see dark lines. Later research showed that these lines were caused by different elements in the sun absorbed a portion of the light. To the pattern of the lines, scientists were able to see which elements (substances and gases) in the sun were present. It became clear that the composition of other stars, astronomers were able to come by analyzing the spectrum. Those stars to know!
Henry Norris Russell (1877-1957)
Russell Henry came from Oyster Bay, New York. He studied at Princeton University in the U.S., then at the University of Cambridge in England and then returned to Princeton to teach there. In 1911, Russell was Professor of Astronomy here. Eleven years later, he was also appointed as a research assistant at the renowned Mount Wilson Observatory in California.
Russell’s research into the life cycle of stars
At the beginning of the 20th century, astronomers were at Harvard University in the U.S. to share their spectrum. Busy star their work came to the attention of Henry Norris Russell, professor of astronomy. He was particularly interested in the life cycle of the stars, and thought the new format could possibly give him. More information in 1913, Russell drew a graph on the basis of data from Harvard. He calculated the position of each star by comparing its brightness. Out hair color because the color of a star indicates the temperature-blue stars are the hottest, red the coolest, he also set the temperature to the brightness out. He discovered that most stars in a diagonal line from top left to bottom right were: the main sequence (see diagram next paragraph).
The Hertzsprung-Russell diagram
There were exceptions. Some stars appeared right corner, which were so cool but bright. They had to be huge so that they do give a lot of light in spite of their coolness. They were called red giants. Some stars appeared below left, who had been so hot, but did not so much light. This was because they had a high density, but were too small to shine brightly. They were called white dwarfs. Astronomers learned to interpret the graph. Slowly they discovered that a star begins its life in the main sequence, where she transforms hydrogen into helium to produce energy. When the supply of hydrogen runs out the star collapsed, causing the core to heat up and the outer layers will expand. The layers then cool down and are red, so that there is a red giant arises. Eventually they float off into space. Only the core remains. The star is a white dwarf and dies in the foreseeable future. The graph Russel, now known as the Hertzsprung-Russell diagram, now called HR diagram is nothing less than a guide to the evolution of stars. The chart is still consulted by many astrophysicists around the world.
Henry Russell was not the first hinted at the existence of the main sequence, red giants and white dwarfs. The Danish astronomer Ejnar Hertzsprung in 1905 had already written articles on the subject in a German magazine, independent of Russell’s findings. Therefore, the graph showing the color and brightness of stars are compared with each other is now known as the Hertzsprung-Russell diagram. Hertzsprung is also known for its contribution to a new, accurate method for calculating the distance between stars and the earth.