Timeline of knowledge about the interstellar and intergalactic medium

Timeline of knowledge about the interstellar medium and intergalactic medium

• 1848 — Lord Rosse studies M1 and names it the Crab Nebula
• 1864 — William Huggins studies the spectrum of the Orion Nebula and shows that it is a cloud of gas
• 1927 — Ira Bowen explains unidentified spectral lines from space as forbidden transition lines
• 1930 — Robert Trumpler discovers absorption by interstellar dust by comparing the angular sizes and brightnesses of globular clusters
• 1944 — Hendrik van de Hulst predicts the 21 cm hyperfine line of neutral interstellar hydrogen
• 1951 — Harold I. Ewen and Edward Purcell observe the 21 cm hyperfine line of neutral interstellar hydrogen^[1]
• 1956 — Lyman Spitzer predicts coronal gas around the Milky Way
• 1965 — James Gunn and Bruce Peterson use observations of the relatively low absorption of the blue component of the Lyman-alpha line from 3C9 to strongly constrain the density and ionization state of the intergalactic medium^[2]
• 1969 — Lewis Snyder, David Buhl, Ben Zuckerman, and Patrick Palmer find interstellar formaldehyde
• 1970 — Arno Penzias and Robert Wilson find interstellar carbon monoxide^[3]
• 1970 — George Carruthers observes molecular hydrogen in space
• 1977 — Christopher McKee and Jeremiah Ostriker propose a three component theory of the interstellar medium
• 1990 — Foreground "contamination" data from the COBE spacecraft provides the first all-sky map of the ISM in microwave bands.

References

1. Ewen, H. I.; Purcell, E. M. (1951), "Observation of a Line in the Galactic Radio Spectrum: Radiation from Galactic Hydrogen at 1,420 Mc./sec.", Nature, 168 (4270): 356, Bibcode:1951Natur.168..356E, doi:10.1038/168356a0 {{citation}}: Unknown parameter |month= ignored (help)
2. Gunn, James E.; Peterson, Bruce A. (1965), "On the Density of Neutral Hydrogen in Intergalactic Space", Astrophysical Journal, 142: 1633–1641, Bibcode:1965ApJ...142.1633G, doi:10.1086/148444 {{citation}}: Unknown parameter |month= ignored (help)
3. Wilson, R. W.; Jefferts, K. B.; Penzias, A. A. (1970), "Carbon Monoxide in the Orion Nebula", Astrophysical Journal, 161: L43, Bibcode:1970ApJ...161L..43W, doi:10.1086/180567 {{citation}}: Unknown parameter |month= ignored (help)