October 27, 1998
The universe is under no obligation to make sense to us, and yet here you are — a collection of atoms that somehow learned to think, to...
Henrietta Leavitt Calibrates the Stars
Birthday · October 27, 1998
A little universe, just for you
Your date.
Ready to give.
Free PNG · 1080 × 1350 · No account needed
Image rights and credit requirements apply when sharing or reusing imagery.
Date & occasion only
Change the year
APOD published October 27, 1998. Full image credits are on the original APOD entry below. A publication-date match, not a photo taken on your date. Independent of NASA.
Humanity's understanding of the relative brightness and variability of stars was revolutionized by the work of Henrietta Swan Leavitt (1868-1921). Working at Harvard College Observatory, Leavitt precisely calibrated the photographic magnitudes of 47 stars to which all other stars could be compared. Leavitt discovered and cataloged over 1500 variable stars in the nearby Magellanic Clouds. From this catalog, Leavitt discovered that brighter Cepheid variable stars take longer to vary, a fact used today to calibrate the distance scale of our universe.