GLOSSARY
DR. EDWARD PICKERING
(1846-1919)
U.S. physicist and astronomer who introduced the use of the meridian photometer to measure the magnitude of stars and established the Harvard Photometry (1884), the first great photometric catalog. In 1876 he was appointed professor of astronomy and director of the Harvard College Observatory. *Fun fact: He graduated from MIT at age 19 and was a professor by 22.
PHOTOGRAPHIC STAR PLATES
These were glass plates that were essentially an early form of photography that captured images of the night sky. The application of photography to astronomical research, in the last quarter of the 19th century, revolutionized the science of the sky. This plate (pictured left) of the Small Magellanic Cloud features notes by Leavitt from her Cepheid variable studies (Credit: Harvard College Observatory, Photographic Glass Plate Collection)
OBAFGKM - “OH! BE A FINE GIRL — KISS ME!”
A mnemonic device created to classify stars developed by Annie Cannon (pictured left). Basically, astronomers realized that the color of a star is determined by its temperature and using this logic Annie created this classification system:
Oh: O class stars are the hottest, with peak temperatures in the ultraviolet part of the spectrum. They have a blue tinge to our eyes; a prime example of an O star is Mintaka, one of the stars in the “belt” of Orion.
Be: B class stars come next, still appearing bluish to us. Rigel, the brightest star in Orion, is a B class star — one you can see and identify easily.
A: A class stars are white-hot; Sirius the Dog Star, the brightest star in the night sky, falls into this category. (Harry Potter fans who are astronomy buffs were unsurprised to learn that Sirius Black could turn into a black dog for that reason.)
Fine: F stars are also white-hot, though with a yellow tinge. Polaris, the North Star, is F class.
Guy/Girl (whichever your preference): G stars are like our Sun: white, but with a more yellow tinge than F stars.
Kiss: K stars are fading towards the red part of the spectrum, and finally
Me: M stars are very red in appearance. Most stars in the universe are M-type.
NOVA
A nova (pl: novae) is a star that suddenly shows an increase in its level of brightness but slowly returns to its original state. This means a nova is a star that suddenly gets very bright for a short period of time.
THEORY OF RELATIVITY
When Einstein's theory of relativity appeared in 1905, it upended centuries of science and gave physicists a new understanding of space and time. Isaac Newton saw space and time as fixed, but in the new picture provided by special relativity and general relativity they were fluid and malleable.
PHOTOMETRY
In astronomy, photometry is the measurement of the brightness of stars and other celestial objects (nebulae, galaxies, planets, etc.). Such measurements can yield large amounts of information on the objects’ structure, temperature, distance, age, etc.
EJNAR HERTZSPRUNG
Ejnar Hertzsprung (1873-1967) was a chemist and astronomer. He is best known for his discovery that some stars (giants) are of much lower density than others (main sequence or “dwarfs”) and for publishing the first color-magnitude diagrams. He was the first to calibrate the period-luminosity relation for Cepheid variable stars and he used it to estimate the distance to the Small Magellanic Cloud.
HENRY DRAPER CATALOGUE
This is a listing of the positions, magnitudes, and spectral types of stars in all parts of the sky. The catalog, named in honour of American astronomer Henry Draper and financed through an endowment by his widow, was compiled at the Harvard College Observatory under the direction of Edward Charles Pickering, mostly by Annie Jump Cannon and Antonia Caetana Maury.
This glossary will be constantly growing and expanding (just like our universe!) If there is something you would like to learn more about, please reach out to our production dramaturg.