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The image also provided new measurements for the mass and diameter of M87*. EHT measured the black hole's mass to be {{val|6.5|0.7|u=billion [[solar masses]]}} and measured the diameter of its event horizon to be approximately {{convert|40|e9km|AU pc ly|abbr=out}}, roughly 2.5 times smaller than the shadow that it casts, seen at the center of the image.<ref name="eso1907"/><ref name="sciencenews"/> Previous observations of M87 showed that the large-scale [[astrophysical jet|jet]] is inclined at an angle of 17° relative to the observer's line of sight and oriented on the plane of the sky at a [[position angle]] of −72°.<ref name="APJL-20190410"/><ref>{{Cite journal|doi = 10.3847/1538-4357/aaafcc|title = The Structure and Dynamics of the Subparsec Jet in M87 Based on 50 VLBA Observations over 17 Years at 43 GHZ|year = 2018|last1 = Walker|first1 = R. Craig|last2 = Hardee|first2 = Philip E.|last3 = Davies|first3 = Frederick B.|last4 = Ly|first4 = Chun|last5 = Junor|first5 = William|journal = The Astrophysical Journal|volume = 855|issue = 2|page = 128|arxiv = 1802.06166|s2cid = 59322635}}</ref> From the enhanced brightness of the southern part of the ring due to [[relativistic beaming]] of approaching funnel wall jet emission, EHT concluded the black hole, which anchors the jet, spins clockwise, as seen from Earth.<ref name="APJL-20190410" /><ref name="aasnova-20190410">{{cite web|url=https://aasnova.org/2019/04/10/first-images-of-a-black-hole-from-the-event-horizon-telescope/|title=First Images of a Black Hole from the Event Horizon Telescope|author=Susanna Kohler|publisher=AAS Nova|date=10 April 2019|accessdate=10 April 2019}}</ref> EHT simulations allow for both prograde and retrograde inner disk rotation with respect to the black hole, while excluding zero black hole spin using a conservative minimum jet power of 10<sup>42</sup> erg/s via the [[Blandford-Znajek process]].<ref name="APJL-20190410" /><ref>R. D. Blandford and R. L. Znajek, "Electromagnetic extraction of energy from Kerr black holes", [http://adsabs.harvard.edu/abs/1977MNRAS.179..433B Mon. Not. R. Astr. Soc. 179:433-456 (1977)].</ref>
[[File:Event Horizon Telescope and Apollo 16.png|thumb|left|A series of images representing the magnification achieved]]
Producing an image from data from an array of radio telescopes requires much mathematical work. Four independent teams created images to assess the reliability of the results.<ref name=imaging>{{cite journal |author=The Event Horizon Telescope Collaboration |year=2019 |journal=Astrophysical Journal Letters |title=First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole |volume=87 |pages=L4 |number=1 |doi=10.3847/2041-8213/ab0e85|bibcode=2019ApJ...875L...4E |arxiv=1906.11241 }}</ref> These methods included both an established algorithm in [[radio astronomy]] for [[image reconstruction]] known as [[CLEAN (algorithm)|CLEAN]], invented by [[Jan Högbom]],<ref name=Högbom1974 >{{Cite journal|last=Högbom|first=Jan A.|date=1974|title=Aperture Synthesis with a Non-Regular Distribution of Interferometer Baselines|journal=Astronomy and Astrophysics Supplement|volume=15|pages=417–426|bibcode=1974A&AS...15..417H}}</ref> as well as self-calibrating [[image processing]] methods<ref name= bnss,etc >SAO/NASA Astrophysics Data System (ADS): [http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1998A%26A...337..325S&db_key=AST&page_ind=12&plate_select=NO&data_type=GIF&type=SCREEN_GIF&classic=YES Seitz, Schneider, and Bartelmann (1998) Entropy-regularized maximum-likelihood cluster mass reconstruction] cites Narayan and Nityananda 1986.</ref> for astronomy such as the [[CHIRP (algorithm)|CHIRP algorithm]] created by [[Katherine Bouman]] and others.<ref name=imaging /><ref>{{Cite web|url=http://social.techcrunch.com/2019/04/10/the-creation-of-the-algorithm-that-made-the-first-black-hole-image-possible-was-led-by-mit-grad-student-katie-bouman/|title=The creation of the algorithm that made the first black hole image possible was led by MIT grad student Katie Bouman|website=TechCrunch|language=en-US|access-date=2019-04-15}}</ref> The algorithms that were ultimately used were a [[regularization (mathematics)|regularized]] [[maximum likelihood]] (RML)<ref n,n1986 >[https://www.annualreviews.org/doi/10.1146/annurev.aa.24.090186.001015 Narayan, Ramesh and Nityananda, Rajaram (1986) "Maximum entropy image restoration in astronomy" ''Annual Review of Astronomy and Astrophysics'' Volume '''24''' (A87-26730 10-90). Palo Alto, CA, Annual Reviews, Inc.] p. 127–170.</ref> algorithm and the [[CLEAN (algorithm)|CLEAN]] algorithm.<ref name="imaging" />
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