Structure above the scale of single stars.
10 topics · 9 curated works
Assumes you know the vocabulary.
Extragalactic Nebulae
Edwin Hubble · 1926
Sorts galaxies into a small number of recurring shapes -- ellipticals, spirals and irregulars -- establishing the classification scheme still used to…
+1 more at this level
Primary sources and full treatments.
3C 273: A Star-Like Object with Large Red-Shift
Maarten Schmidt · 1963
Identifies the puzzling spectral lines of a starlike radio source as ordinary hydrogen lines redshifted far more than any star could be, revealing…
+6 more at this level
9 works
Edwin Hubble
Sorts galaxies into a small number of recurring shapes -- ellipticals, spirals and irregulars -- establishing the classification scheme still used to describe galaxy morphology.
link checked 17 Sept 2026George O. Abell
Catalogues thousands of rich galaxy clusters from photographic sky surveys and shows their distribution is not random, founding the systematic study of large-scale clustering.
link checked 17 Sept 2026Maarten Schmidt
Identifies the puzzling spectral lines of a starlike radio source as ordinary hydrogen lines redshifted far more than any star could be, revealing the first quasar.
link checked 17 Sept 2026D. Lynden-Bell
Argues that quasars are powered by gas falling onto massive collapsed objects at galaxy centres, and that most nearby galaxies should harbour the dead, starved remnants of the same engine.
Rubin & Ford
Measures Andromeda's rotation curve and finds it stays flat far beyond where the visible disk should make it fall off, evidence that most of the galaxy's mass is invisible.
link checked 17 Sept 2026McKee & Ostriker
Argues the gas between stars is not one uniform substance but three interlocking phases whose proportions are set by the rate of supernova explosions.
link checked 17 Sept 2026White & Rees
Proposes that galaxies form in two stages, gas cooling and condensing inside dark matter halos that assembled first, setting the template for hierarchical structure formation.
link checked 17 Sept 2026Bland-Hawthorn & Gerhard
Assembles the Milky Way's disk, bulge and halo into a single structural picture and argues our own galaxy is best understood by comparison with external spirals rather than in isolation.
link checked 17 Sept 2026Event Horizon Telescope Collaboration
Presents the first direct image of a black hole's shadow, arguing the ring of light around M87's centre matches general relativity's prediction for an event horizon.
link checked 17 Sept 2026