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The Astronomer Who Brought Us the Universe
StartsWithABang writes If all we were able to do was look up at the sky and see what we can see, no matter how powerful our instruments became, we would be extraordinarily limited in what we could learn about the Universe. But if we could know some intrinsic properties about what we were looking at, then simply by measuring things like how bright these objects appear, we could figure out the cosmic distance scale; all it would require is knowledge of a "distance indicator" or "standard candle." The very first one ever discovered — by Henrietta Leavitt — is not only still in use today, but taught us the galactic nature of the spiral nebulae and gave us the expanding Universe.
Leavitt's discovery is on a par with Galileo's discovery of the moons of Jupiter in changing our view of the universe. It combined a brilliant insight, that all the stars in the Small Magellanic Cloud are at about the same distance from Earth, and a lot of hard work analyzing photographic plates. Her measurement tool is still the main one used to determine cosmic distances from beyond the range of stellar parallax out to nearby galaxies, and is used, in turn, to calibrate Type Ia supernova, the standard candle for probing deep into intergalactic space, and back to the Big Bang. Another example of women astronomers getting less recognition than they deserve is Jocelyn Bell, who discovered millisecond pulsars and whose thesis advisor won the Nobel Prize for that discovery.