Timeline A timeline is a display of a list of events in chronological order. It is typically a graphic design showing a long bar labelled with dates paralleling it, and usually contemporaneous events. Timelines can use any suitable scale represen ...

of knowledge about the interstellar medium and

intergalactic medium Intergalactic may refer to: * "Intergalactic" (song), a song by the Beastie Boys * ''Intergalactic'' (TV series), a 2021 UK science fiction TV series * Intergalactic space * Intergalactic travel, travel between galaxies in science fiction and ...

* 1848 — Lord Rosse studies M1 and names it the Crab Nebula. The telescope is much larger than the small refactors typical of this period and it also reveals the spiral nature of M51. * 1864 —

William Huggins Sir William Huggins (7 February 1824 – 12 May 1910) was an English astronomer best known for his pioneering work in astronomical spectroscopy together with his wife, Margaret. Biography William Huggins was born at Cornhill, Middlesex, in ...

studies the

spectrum A spectrum (plural ''spectra'' or ''spectrums'') is a condition that is not limited to a specific set of values but can vary, without gaps, across a continuum. The word was first used scientifically in optics to describe the rainbow of colors ...

of the Orion Nebula and shows that it is a cloud of gas * 1904 — Interstellar calcium detected on spectrograph at Potsdam * 1909 — Slipher confirms Kapteyn's theory of interstellar gas * 1912 — Slipher confirms interstellar dust * 1927 — Ira Bowen explains unidentified

spectral line A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from emission or absorption of light in a narrow frequency range, compared with the nearby frequencies. Spectral lines are often used to iden ...

s from space as forbidden transition lines * 1930 —

Robert Trumpler Robert Julius Trumpler (until 1915 Robert Trümpler, born October 2, 1886 in Zürich, Switzerland; died September 10, 1956 in Berkeley, California, Berkeley, United States) was a Switzerland, Swiss-United States, American astronomer. Career After ...

discovers absorption by

interstellar dust Cosmic dust, also called extraterrestrial dust, star dust or space dust, is dust which exists in outer space, or has fallen on Earth. Most cosmic dust particles measure between a few molecules and 0.1 mm (100 micrometers). Larger particles are c ...

by comparing the angular sizes and brightnesses of

globular cluster A globular cluster is a spheroidal conglomeration of stars. Globular clusters are bound together by gravity, with a higher concentration of stars towards their centers. They can contain anywhere from tens of thousands to many millions of membe ...

s * 1944 —

Hendrik van de Hulst Hendrik Christoffel "Henk" van de Hulst (19 November 1918 – 31 July 2000) was a Dutch astronomer and mathematician. In 1944, while a student in Utrecht, he predicted the existence of the 21 cm hyperfine line of neutral interstellar hydrogen. ...

predicts the 21 cm hyperfine line of neutral interstellar

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

* 1951 — Harold I. Ewen and Edward Purcell observe the 21 cm

hyperfine In atomic physics, hyperfine structure is defined by small shifts in otherwise degenerate energy levels and the resulting splittings in those energy levels of atoms, molecules, and ions, due to electromagnetic multipole interaction between the nuc ...

line of neutral interstellar hydrogen * 1956 —

Lyman Spitzer Lyman Spitzer Jr. (June 26, 1914 – March 31, 1997) was an American theoretical physicist, astronomer and mountaineer. As a scientist, he carried out research into star formation, plasma physics, and in 1946, conceived the idea of telesco ...

predicts coronal gas around the

Milky Way The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. ...

* 1965 —

James Gunn James Francis Gunn Jr. (born August 5, 1966) is an American filmmaker and executive. He began his career as a screenwriter in the mid-1990s, starting at Troma Entertainment with ''Tromeo and Juliet'' (1997). He then began working as a directo ...

and Bruce Peterson use observations of the relatively low absorption of the blue component of the

Lyman-alpha line The Lyman-alpha line, typically denoted by Ly-α, is a spectral line of hydrogen (or, more generally, of any one-electron atom) in the Lyman series. It is emitted when the atomic electron transitions from an ''n'' = 2 orbital to the gro ...

from 3C9 to strongly constrain the density and ionization state of the intergalactic medium * 1969 — Lewis Snyder, David Buhl, Ben Zuckerman, and Patrick Palmer find interstellar formaldehyde * 1970 —

Arno Penzias Arno Allan Penzias (; born April 26, 1933) is an American physicist, radio astronomer and Nobel laureate in physics. Along with Robert Woodrow Wilson, he discovered the cosmic microwave background radiation, which helped establish the Big Bang ...

and Robert Wilson find interstellar

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

* 1970 — George Carruthers observes

molecular hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, ...

in space * 1977 —

Christopher McKee Christopher Fulton McKee (born 1942) is an astrophysicist. McKee attended Phillips Academy and Harvard University, and obtained a Ph.D. from the University of California, Berkeley (UCB) in 1970 under advisor George B. Field. In 1974, he was app ...

and

Jeremiah Ostriker Jeremiah Paul "Jerry" Ostriker (born April 13, 1937) is an American astrophysicist and a professor of astronomy at Columbia University and is the Charles A. Young Professor ''Emeritus'' at Princeton where he also continues as a senior research s ...

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 Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ra ...

bands.

References

Interstellar and intergalactic medium Astrochemistry {{Astronomy-stub