Editing Einstein Observatory (section)

==Scientific results==
Einstein discovered approximately five thousand sources of x-ray emission during its operation{{sfn|Schlegel|2002|p=22-23}} and was the first x-ray experiment able to resolve an image of the observed sources.

===X-ray background===
Surveys by early x-ray astronomy experiments showed a [[X-ray background|uniform diffuse background of x-ray radiation]] across the sky. The uniformity of this background radiation indicated that it originated outside of the [[Milky Way Galaxy]], with the most popular hypotheses being a hot gas spread uniformly throughout space, or numerous distant point sources of x-rays (such as [[quasar]]s) that appear to blend together due to their great distance. Observations with Einstein showed that a large portion of this x-ray background originated from distant point sources, and observations with later x-ray experiments have confirmed and refined this conclusion.{{sfn |Tucker |Tucker |1986 |p=93-95}}

===Stellar x-ray emissions===
Observations with Einstein showed that all stars emit x-rays.{{sfn|Schlegel|2002|p=31}} [[Main sequence]] stars emit only a small portion of their total radiation in the x-ray spectrum, primarily from their [[stellar corona|corona]], while [[neutron star]]s emit a very large portion of their total radiation in the x-ray spectrum.{{sfn |Tucker |Tucker |1986 |p=93-95}} Einstein data also indicated that coronal x-ray emissions in main sequence stars are stronger than was expected at the time.<ref name="nasa">{{cite web |title=The Einstein Observatory (HEAO-2) |author=<!--Not stated--> |date=2020 |publisher=National Aeronautics and Space Administration |url=https://heasarc.gsfc.nasa.gov/docs/einstein/heao2.html |access-date=July 8, 2021}}</ref>

===Galaxy clusters===
The [[Uhuru (satellite)|Uhuru]] satellite discovered x-ray emissions from a hot, thin gas pervading distant [[galaxy cluster|clusters of galaxies]]. Einstein was able to observe this gas in greater detail. Einstein data indicated that the containment of this gas within these clusters by gravity could not be explained by the visible matter within those clusters, which provided further evidence for studies of [[dark matter]]. Observations by Einstein also helped to determine the frequency of irregularly-shaped clusters compared to round, uniform clusters.{{sfn |Tucker |Tucker |1986 |p=93-95}}

===Galactic jets===
Einstein detected [[astrophysical jet#Relativistic jet|jets of x-rays]] emanating from [[Centaurus A]] and [[Messier 87|M87]] that were aligned with previously-observed jets in the radio spectrum.<ref name="nasa">{{cite web |title=The Einstein Observatory (HEAO-2) |author=<!--Not stated--> |date=2020 |publisher=National Aeronautics and Space Administration |url=https://heasarc.gsfc.nasa.gov/docs/einstein/heao2.html |access-date=July 8, 2021}}</ref>

<gallery mode=packed heights=220>
File:HEAO-2 Image of the Eta Carinae Nebula Taken by the High Energy Astronomy Observatory 7995526.jpg|[[Eta Carinae Nebula]]
File:HEAO-2 Image of the Black Hole, Cygnus X-1, Taken by the High Energy Astronomy Observatory 8003548.jpg|[[Cygnus X-1]]
File:HEAO-2 Image of the Supernova Remnant Cassiopeia A Taken by the High Energy Astronomy Observatory 8003547.jpg|[[Supernova]] remnant [[Cassiopeia A]]
</gallery>