Henrietta Leavitt

HENRIETTA LEAVITT

BIOGRAPHY

740L HENRIETTA LEAVITT

MEASURING DISTANCE IN THE UNIVERSE

Born Died July 4, 1868 December 12, 1921 Lancaster, Massachusetts Cambridge, Massachusetts By Cynthia Stokes Brown, adapted by Newsela Henrietta Swan Leavitt studied distant stars that dim and brighten. She was able to determine how bright these stars were and how far away they were. Her work greatly helped other astronomers. They were able to measure huge distances in space, find new galaxies, and begin mapping the Universe.

2 3 Henrietta Swan Leavitt studied distant stars that dim and brighten. She was Leavitt studied thousands of photographs of these stars. They were called able to determine how bright these stars were and how far away they were. Cepheid variables. She discovered a way to figure out how bright they wereand how far away they were. Her work greatly helped other astronomers. They were able to measure huge distances in space, find new galaxies, and begin mapping the Universe. She found that the longer a star’s period, the brighter it was. Leavitt com- pared how bright a star appeared, and how bright it actually was. She Leavitt was a minister’s daughter. Her family moved frequently. could estimate how far away the star actually was this way.

She went to the Society for Collegiate Instruction of Women. It was her Leavitt published her first paper on the period-brightness relationship in dream to attend. In her senior year, she found that she loved astronomy. 1908. Four years later, she published a table of the periods of 25 Cepheid variables.

In 1921, she died of cancer at age 53 in Cambridge, Massachusetts. At the Harvard College Observatory

After graduation, Leavitt became a volunteer at the Harvard College Obser- vatory. She worked as a computer. At that time “computers” were women Leavitt’s Legacy who looked at tiny dots on photographs of the night sky. They kept detailed records of the stars and planets in notebooks. Before Leavitt, astronomers could only measure distances up to 100 light years away. Her discovery improved their ability. They were now able to pin- Leavitt was then hired at 30 cents an hour. She worked at the observatory point some objects at 100,000 light years away. These objects were farther for the rest of her life. away than anyone had imagined. It meant they could not be within our Milky Way galaxy.

Edwin Hubble was studying Cepheid variables near Los Angeles. He used Using Cepheid variables Leavitt’s findings and a new telescope to find Cepheid variables that were extremely far away. They were so far away that they could not be in our One of Leavitt’s jobs was to examine variable stars. These stars change galaxy. their brightness. Most stars don’t. By 1925, most astronomers agreed that our galaxy is just one of many. Leavitt discovered 2,400 new variable stars. Leavitt’s work faced challenges. Her first director at Harvard only wanted Some variable stars dim and brighten on a regular schedule. This is called his staff to collect information. He didn’t want them try and put the infor- their “period.” This period can range from one day to four months. mation together as a theory. Another director tried to take some credit for her work after her death. Yet today, Leavitt is seen as someone who helped us understand the size of the Universe.

4 5 Timeline of Leavitt’s life

1902–1921 Paid work at Harvard College Observatory; gradually loses her hearing

1868 1893–1902 1902–1908 Born on July 4 Volunteer work Discovers 2400 Cepheid variable stars in Lancaster, MA at Harvard College and develops her period-luminosity theory Observatory

1888–1892 1908 Attends the Society for Publishes her theory on the correlation between Collegiate Instruction of period and luminosity in Cepheid variables Women (Radcliffe/Harvard)

1885–1888 1912 1921 Attends Oberlin College Publishes a table Dies of cancer on of 25 different Cepheid December 12 variable periods in Cambridge, MA

8 9 10 18701 2 3 4 5 6 7 8 9 10 18801 2 3 4 5 6 7 8 9 10 18901 2 3 4 5 6 7 8 9 10 19001 2 3 4 5 6 7 8 9 10 19101 2 3 4 5 6 7 8 9 10 19201 2 3 4 5 6 7 8 9 10

1876 1920 Telephone 1889 1898 Women in the patented Vincent van Gogh Marie Curie discovers United States gain paints Starry Night radium and polonium the right to vote

1870 1882 1916 Undersea cables connect Naturalist Charles Darwin Albert Einstein publishes his Europe, North America, and India dies in Kent, England General Theory of Relativity 1869 Dmitri Mendeleev devises 1914 the periodic table World War I begins

During the time of Leavitt A modest life

Leavitt never married. She gradually became deaf, starting with an illness she had as a young adult. She was buried in Cambridge in the family plot. All she left was worth $314.91.

Upon her death, someone who worked with her wrote: “[She] was pos- sessed of a nature so full of sunshine that, to her, all of life became beauti- fied and full of meaning.”

8 9 Image credits

Articles leveled by Newsela have been adjusted along several dimensions of text complexity including sentence structure, vocabulary and organization. The number followed by L indicates the Lexile measure of the article. For more information on Lexile measures and how they correspond to grade levels: http://www.lexile.com/about-lexile/lexile-overview/

To learn more about Newsela, visit www.newsela.com/about.

The Lexile® Framework for Reading The Lexile® Framework for Reading evaluates reading ability and text complexity on the same developmental scale. Unlike other measurement systems, the Lexile Framework determines reading ability based on actual assessments, rather than generalized age or grade levels. Recognized as the standard for matching readers with texts, tens of millions of students worldwide receive a Lexile measure that helps them find targeted readings from the more than 100 million articles, books and websites that have been measured. Lexile measures connect learners of all ages with resources at the right level of challenge and monitors their progress toward state and national proficiency standards. More information about the Lexile® Framework can be found at www.Lexile.com.

10 11