Assertion: hourglass nebula | /r/HasProperty | discovered by margaret w. mayall
Facets:
value: between 1918
type: TEMPORAL
value: between 1924
type: TEMPORAL
Source sentences:
text: The Hourglass Nebula was discovered by Annie Jump Cannon and Margaret W. Mayall between 1918 and 1924, during their work on an extended Henry Draper Catalogue, an astronomical star catalogue providing spectroscopic classifications for hundreds of thousands of stars.