April's theme is a famous scientist: Henrietta Swan Leavitt.
Her name should sound slightly more familiar than the first time I mentioned it (Ada Lovelace day, remember?) - basically, she discovered Cepheid variables, which allowed Edwin Hubble to measure distances between stars, planets and galaxies.
OK, I'm wondering too: "what the heck is a Cepheid variable?" - lucky for you, I went to look it up & will tell you.
A Cepheid variable is actually a star. A unique star that pulsates, changing in size and brightness (luminosity) as it does so. What makes a variable star a Cepheid is the relationship between the luminosity and period - in other words, the star will become brightest (and dimmest) at a distinct interval, every few days for example. It's like a sine (or cosine) curve, which I'm showing at the left - imagine the line is the luminosity - it increases and decreases to the same levels every time - and it does so in the same amount of time each time. Somehow this is used as a ruler to measure distances in the Universe. I don't understand how, but it's pretty neat! Makes me want to finish my degree & restart in Mathematics & Astronomy...
Anyway, Henrietta discovered these stars while working at Harvard College Observatory. She started working there in 1893 & published her findings in 1908 - only 15 years, which is pretty impressive when you find out what she was doing. She was employed as a computer. Yep, before the PC, a computer was actually a job you could have. She was actually part of "Pickering's Harem," the first group of women computers (previously only a man's job)... this of course allowed the men to do all the fun work - women still weren't allowed to use the telescope.
(stepping down from soapbox) So Henrietta was a computer - she measured and catalogued the brightness of stars from photographic plates taken at the observatory. That's how she noticed that brighter stars had longer periods - by staring at little dots, comparing their size and brightness. After a while, I think I would start to wonder if I were really measuring differences or just seeing things!
After that, Henrietta's health took a turn for the worse. She never fully recovered, probably due to the medical practices at the time. She was made head of Stellar Photometry (doesn't that sound awesome?) at the observatory in 1921 but died later that year of cancer. You can help but feel sorry for her: she struggled her whole life, making only $10 a week as an assistant, never married, no children - and in the end, no recognition for her work during her own lifetime.