Henry Draper Catalogue

The Henry Draper Catalogue is a catalog of stellar spectra and spectral classifications produced at Harvard College Observatory and published in nine volumes from 1918 to 1924.

Stellar spectrum: The wavelength-dependent light emitted by a star, shaped by its temperature, composition, and motion. The catalogue organizes stars by patterns in their spectra.
Objective-prism spectroscopy: A method that places a prism before a telescope objective to record spectra for many field stars at once. It enabled Harvard astronomers to photograph spectra across broad regions of sky.
Henry Draper: An American physician and astronomer who made early astronomical photographs and obtained the first photograph of a stellar spectrum. His widow funded the Harvard project and the catalogue bears his name.
Henry Draper Extension: A later continuation of the Henry Draper Catalogue that added spectral classifications for additional stars. It extended the catalogue’s coverage beyond its original publication.
Stellar classification: The grouping of stars by measurable properties such as spectra, temperature, luminosity, or evolutionary state. The catalogue’s central achievement was assigning spectral types to stars.
Spectrograph: An instrument that separates light into wavelengths and records or measures the resulting spectrum. Spectrographs produced the dispersed stellar light classified in the catalogue.
Mary Anna Draper: An American philanthropist who supported astronomical research in memory of her husband, Henry Draper. Her endowment financed the work that produced the catalogue.
Henry Draper Catalogue Extension Charts: A published set of charts accompanying the Henry Draper Extension and locating its classified stars. The charts made the extended catalogue’s stellar identifications usable on the sky.
Harvard spectral classification: A stellar classification system organized mainly by spectral features and later reordered into the O–B–A–F–G–K–M sequence. Its system supplied the spectral letters used throughout the catalogue.
Annie Jump Cannon: An American astronomer who classified stellar spectra and established the familiar O–B–A–F–G–K–M sequence. Cannon’s classifications shaped the system applied to the catalogue’s stars.

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