We have become so accustomed to the vastness of our universe that it’s easy to forget how little we knew about its scope as recently as 1900. Astronomers didn’t even have a reliable yardstick for measuring distances in the cosmos, until an obscure female astronomer made a groundbreaking discovery while combing through photographic plates with snapshots of the stars in the night sky.

That discovery provides the main storyline for Silent Sky, a new play now making its world premiere at the South Coast Repertory in Costa Mesa, California. Written by Lauren Gunderson, it is is based on the life of Henrietta Leavitt: the woman who figured out how to measure the universe.

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Born in 1868 in Cambridge, Massachusetts, Henrietta Leavitt was the daughter of a Congressional minister, descended from a long line of New England Puritans.

She attended both Oberlin College and what would later become Radcliffe College, although she didn’t discover astronomy until her senior year. An illness that left her mostly deaf sidelined her for several years, but her love for the stars remained undiminished. She started volunteering at the Harvard College Observatory, just to be near her passion.

The observatory director at the time, Charles Pickering, had become frustrated at the less-than-stellar work of his male assistants when it came to counting the images of stars on photographic plates. It was tedious work, perhaps resented by young male astronomers.

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Pickering famously declared his housekeeper could do better. And so he brought in his housekeeper, Williamina Fleming, to prove it. She didn’t disappoint; indeed, Fleming is credited with making most of the classifications in the Draper Catalogue of Stellar Spectra, first published in 1890.

Pickering soon amassed an entire team of female astronomical “computers” — dubbed “Pickering’s Harem” — including Annie Jump Cannon. Leavitt joined their ranks officially in 1902, at a salary of 30 cents an hour.

Given the prejudices against women in science at the time, Leavitt technically wasn’t allowed to do any true research, or even use the telescope. But as Leavitt diligently pored over the plates, she began noticing more and more Cepheid variables in the Small Magellanic Cloud — a type of periodically pulsing star once believed to be quite rare. She personally discovered more than 2400 variable stars, roughly half of all those known during her day.

But Leavitt’s biggest claim to astronomical fame is known as the “Period-Luminosity Relation.” She studied 1777 variable stars, and figured out that the total amount of radiation a Cepheid variable gives off in one second (its luminosity) is related to the length of time between pulses (period of pulsation) — that is, if you knew how long it took for the star to go from bright to dim, this would tell you how bright it actually was.

And once you knew that, you had a much better means of measuring distance. Before Leavitt’s discovery, astronomers were limited to determining distances of stars at 100 light years; after, that range increased to 10 million light years. Her work became the basis of Ejnar Hertzsprung’s plot of the distance of stars, and for Edwin Hubble’s determination of the age of the universe, for example. Alas, Leavitt died of cancer in December 1921, shortly after being promoted to head of stellar photometry.

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This is the second play featuring a woman scientist penned by Gunderson. She also wrote Emilie: La Marquise du Chatelet Defends Her Life, based on 18th century French mathematician (and lover of Voltaire) Emilie du Chatelet, which premiered at SCR in 2009.

Leavitt’s life was far less dramatic than du Chatelet’s. An obituary by her colleague, Solon Bailey, describes her devotion to her family and “sense of duty, justice and loyalty… For light amusements she cared little.” There’s not much there that requires defending, but Gunderson nonetheless weaves a compelling tale out of this most quiet life.

Sure, there are some historical liberties, notably the addition of a love interest: a (fictional) astronomer named Peter Shaw who recognizes how extraordinary Henrietta truly is. It’s to Gunderson’s credit that she portrays so well the passion Leavitt had for the sky, and her consuming desire to finally “know where we are in the universe.” (A highlight is the moment when Leavitt figures out the pattern of those pulsing Cepheids while listening to her sister playing the piano.) Gunderson also captures the dilemma of limited options available to highly intelligent women of that era, particularly the frustration Leavitt must have felt not to be allowed to fully participate in the scientific pursuits she loved so much.

Hubble often said Leavitt deserved the Nobel Prize for her work, and Gosta Mittag-Leffler of the Swedish Academy of Sciences actually wrote to Harlow Shapley, who succeeded Pickering as director of the Harvard Observatory, to begin the paperwork for her nomination in 1924. He was distressed to learn of her death three years earlier, making her ineligible for the Nobel Prize.

(Shapley, in a less than noble moment, had the gall to suggest, in his reply, that he should receive the credit for the interpretation of her findings. To his credit, Mittag-Leffler didn’t fall for it; Shapley never won the Nobel Prize, either.)

“No diary has been found recording what it was about the stars that moved her,” George Johnson wrote in his 2005 biography, Miss Leavitt’s Stars: The Untold Story of the Woman Who Discovered How to Measure the Universe. “One of history’s small players, her story has been allowed to slip through the cracks….” Fortunately for us, Lauren Gunderson brings Henrietta Leavitt vividly to life and lets us catch a glimpse of a truly remarkable woman who deserved better than to remain lost in obscurity.

Silent Sky runs through May 1, 2011. You can find performance times and ticket information here.

Photos: (top) Colette Kilroy as Annie Jump Cannon, Amelia White as Willamina Fleming, and Monette Magrath as Henrietta Leavitt in South Coast Repertory’s 2011 world premiere of Silent Sky. Credit: South Coast Repertory. (center) “Pickering’s Harem” at the Harvard College Observatory, circa 1900-1910. Credit: Grasslands Observatory via Wikimedia Commons. (bottom) Henrietta Swan Leavitt. Source: American Institute of Physics, Emilio Segrè Visual Archives