Editing Dark matter (section)

=== 1970s ===
The hypothesis of dark matter largely took root in the 1970s. Several different observations were synthesized to argue that galaxies should be surrounded by halos of unseen matter. In two papers that appeared in 1974, this conclusion was drawn in tandem by independent groups: in [[Princeton, New Jersey]], by [[Jeremiah Ostriker]], [[Jim Peebles]], and [[Amos Yahil]], and in Tartu, Estonia, by [[Jaan Einasto]], [[Enn Saar]], and [[Ants Kaasik]].<ref name=DeSwart2024>{{cite journal |last1=de Swart |first1=Jaco |date=1 August 2024 |title=Five decades of missing mass |journal=[[Physics Today]] |volume=77 |pages=34–43 | doi=10.1063/pt.ozhk.lfeb |doi-access=free }}</ref>

One of the observations that served as evidence for the existence of galactic halos of dark matter was the shape of [[galaxy rotation curve]]s. These observations were done in optical and radio astronomy. In optical astronomy, [[Vera Rubin]] and [[Kent Ford (astronomer)|Kent Ford]] worked with a new [[spectrograph]] to measure the [[galaxy rotation curve|velocity curve]] of edge-on [[spiral galaxy|spiral galaxies]] with greater accuracy.<ref name=NYT-20161227>{{cite news |last=Overbye |first=D. |author-link=Dennis Overbye |date=27 December 2016 |title=Vera Rubin, 88, dies; opened doors in astronomy, and for women |type=obituary |newspaper=[[The New York Times]] |url=https://www.nytimes.com/2016/12/27/science/vera-rubin-astronomist-who-made-the-case-for-dark-matter-dies-at-88.html |access-date=27 December 2016 }}</ref><ref>{{cite web |title=First observational evidence of dark matter |website=Darkmatterphysics.com |url=http://www.darkmatterphysics.com/Galactic-rotation-curves-of-spiral-galaxies.htm |access-date=6 August 2013 |archive-url=https://web.archive.org/web/20130625183052/http://www.darkmatterphysics.com/Galactic-rotation-curves-of-spiral-galaxies.htm |archive-date=25 June 2013}}</ref><ref name=Rubin1970>{{cite journal |last1=Rubin |first1=V.C. |author1-link=Vera Rubin |last2=Ford |first2=W.K. Jr. |author2-link=Kent Ford (astronomer) |date=February 1970 |title=Rotation of the Andromeda nebula from a spectroscopic survey of emission regions |journal=[[The Astrophysical Journal]] |volume=159 |pages=379–403 |bibcode=1970ApJ...159..379R |doi=10.1086/150317 |s2cid=122756867 }}</ref>

At the same time, radio astronomers were making use of new [[Radio telescope|radio telescopes]] to map the [[21 cm line|21&nbsp;cm line]] of [[atomic hydrogen]] in nearby galaxies. The radial distribution of interstellar atomic hydrogen ([[H I region|H{{sup|{{math|I}}}}]]) often extends to much greater galactic distances than can be observed as collective starlight, expanding the sampled distances for rotation curves – and thus of the total mass distribution – to a new dynamical regime. Early mapping of [[Andromeda galaxy|Andromeda]] with the {{convert|300|ft|m|adj=mid}} telescope at [[Green Bank Observatory|Green Bank]]<ref name=Roberts1966>{{cite journal |last1=Roberts |first1=Morton S. <!-- |author-link1=Morton S. Roberts (astronomer) --> |date=May 1966 |title=A high-resolution 21&nbsp;cm hydrogen-line survey of the Andromeda nebula |journal=[[The Astrophysical Journal]] |volume=159 |pages=639–656 |bibcode=1966ApJ...144..639R |doi=10.1086/148645}}</ref> and the {{convert|250|ft|m|adj=mid}} dish at [[Jodrell Bank Observatory|Jodrell Bank]]<ref name="Gottesman1966">{{cite journal |last1=Gottesman |first1=S. T. <!-- |author-link1=S. T. Gottesman (astronomer) --> |last2=Davies |first2=Rod D. |author-link2=Rod Davies |last3=Reddish |first3=Vincent Cartledge |author-link3=Vincent Cartledge Reddish |date=1966 |title=A neutral hydrogen survey of the southern regions of the Andromeda nebula |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=133 |issue=4 |pages=359–387 |bibcode=1966MNRAS.133..359G |doi=10.1093/mnras/133.4.359 |doi-access=free}}</ref> already showed the H{{sup|{{math|I}}}} rotation curve did not trace the decline expected from Keplerian orbits.

As more sensitive receivers became available, <!-- [[Morton S. Roberts|-->Roberts<!--]]--> & <!-- [[Robert N. Whitehurst (astronomer) --- not the Olympic sailor --- |-->Whitehurst<!--]]--> (1975)<ref name=Roberts1975>{{cite journal |last1=Roberts |first1=Morton S.  <!-- |author-link1=Morton S. Roberts |last2=Whitehurst |first2=Robert N.  |author-link2=Robert N. Whitehurst (astronomer) --> |date=October 1975 |title=The rotation curve and geometry of M&nbsp;31 at large galactocentric distances |journal=[[The Astrophysical Journal]] |volume=201 |pages=327–346 |bibcode=1975ApJ...201..327R |doi=10.1086/153889}}</ref> were able to trace the rotational velocity of Andromeda to 30&nbsp;kpc, much beyond the optical measurements. Illustrating the advantage of tracing the gas disk at large radii; that paper's ''Figure&nbsp;16''<ref name=Roberts1975/> combines the optical data<ref name=Rubin1970/> (the cluster of points at radii of less than 15&nbsp;kpc with a single point further out) with the H{{sup|{{math|I}}}} data between 20 and 30&nbsp;kpc, exhibiting the flatness of the outer galaxy rotation curve; the solid curve peaking at the center is the optical surface density, while the other curve shows the cumulative mass, still rising linearly at the outermost measurement. In parallel, the use of interferometric arrays for extragalactic H{{sup|{{math|I}}}} spectroscopy was being developed. <!-- [[David H. Rogstad (astronomer)| -->Rogstad<!-- ]] --> & [[Seth Shostak|Shostak]] (1972)<ref name=Rogstad1972/> published H{{sup|{{math|I}}}} rotation curves of five spirals mapped with the Owens Valley interferometer; the rotation curves of all five were very flat, suggesting very large values of mass-to-light ratio in the outer parts of their extended H{{sup|{{math|I}}}}&nbsp;disks.<ref name="Rogstad1972">{{cite journal |last1=Rogstad |first1=David H. <!-- |author-link1=David H. Rogstad (astronomer) --> |last2=Shostak |first2=G. Seth |author-link2=Seth Shostak |date=September 1972 |title=Gross properties of five Scd galaxies as determined from 21&nbsp;centimeter observations |journal=[[The Astrophysical Journal]] |volume=176 |pages=315–321 |bibcode=1972ApJ...176..315R |doi=10.1086/151636}}</ref> In 1978, Albert Bosma showed further evidence of flat rotation curves using data from the [[Westerbork Synthesis Radio Telescope]].<ref>{{cite thesis |last=Bosma |first=A. |date=1978 |title=The distribution and kinematics of neutral hydrogen in spiral galaxies of various morphological types |degree=Ph.D. |publisher=[[Rijksuniversiteit Groningen]] |url=http://nedwww.ipac.caltech.edu/level5/March05/Bosma/frames.html}}</ref>

In 1978, [[Gary Steigman|Steigman]] et al.<ref>{{cite journal |last=Gunn |first=J. E. |last2=Lee |first2=B. W. |last3=Lerche |first3=I. |last4=Schramm |first4=D. N. |last5=Steigman |first5=G. |date=Aug 1978 |title=Some astrophysical consequences of the existence of a heavy stable neutral lepton. |url=https://ui.adsabs.harvard.edu/abs/1978ApJ...223.1015G/abstract |journal=The Astrophysical Journal |language=en |volume=223 |pages=1015–1031 |doi=10.1086/156335 |issn=0004-637X}}</ref> presented a study that extended earlier cosmological relic-density calculations to any hypothetical stable, electrically neutral, weak-scale lepton, showing how such a particle's abundance would "freeze out" in the [[Early universe|early Universe]] and providing analytic expressions that linked its mass and weak interaction cross-section to the present-day matter density. By decoupling the analysis from specific [[neutrino]] properties and treating the candidate generically, the authors set out a framework that later became the standard template for [[weakly interacting massive particle]]s (WIMPs)<ref>{{cite book |last=Tan |first=Chung-i |url=https://www.google.com.br/books/edition/Particles_Strings_And_Supernovae_Proceed/CtBKDwAAQBAJ |title=Particles, Strings And Supernovae - Proceedings Of Theoretical Advanced Study Institute In Elementary Particle Physics (In 2 Volumes) |last2=Jevicki |first2=Antal |date=1989-05-01 |publisher=World Scientific |isbn=978-981-4590-77-8 |pages=191 |language=en}}</ref> and for comparing [[Particle physics|particle-physics]] models with cosmological constraints. Though subsequent work has refined the methodology and explored many alternative candidates, this paper marked the first explicit, systematic treatment of dark matter as a new particle species beyond the [[Standard Model]].<ref>{{citation |last=Mambrini |first=Yann |title=Introduction |date=2021 |work=Particles in the Dark Universe: A Student’s Guide to Particle Physics and Cosmology |pages=1–22 |editor-last=Mambrini |editor-first=Yann |url=https://link.springer.com/chapter/10.1007/978-3-030-78139-2_1 |access-date=2025-04-26 |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-030-78139-2_1 |isbn=978-3-030-78139-2}}</ref> 

By the late 1970s the existence of dark matter halos around galaxies was widely recognized as real, and became a major unsolved problem in astronomy.<ref name=DeSwart2024/>