A picture may be worth a thousand words, but for astronomers, simply recording images of stars and galaxies isn't enough. To measure the true size and absolute brightness (luminosity) of heavenly bodies, astronomers need to accurately gauge the distance to these objects. To do so, the researchers rely on "standard candles"—stars whose luminosities are so well known that they act like light bulbs of known wattage. One way to determine a star's distance from Earth is to compare how bright the star appears in the sky to its luminosity.