Event Horizon Telescope#Messier 87*

File:EHT-infography.png. Analogue signals collected by the antenna are converted to digital signals and stored on hard drives together with the time signals provided by the atomic clock. The hard drives are then shipped to a central location to be synchronized. An astronomical observation image is obtained by processing the data gathered from multiple locations.]]

File:EHTobservations2017.jpg)]]

File:Sagittarius A*.jpg image of Sagittarius A* (center) and two light echoes from a recent explosion (circled)]]

The EHT is composed of many radio observatories or radio-telescope facilities around the world, working together to produce a high-sensitivity, high-angular-resolution telescope. Through the technique of very-long-baseline interferometry (VLBI), many independent radio antennas separated by hundreds or thousands of kilometres can act as a phased array, a virtual telescope which can be pointed electronically, with an effective aperture which is the diameter of the entire planet, substantially improving its angular resolution.{{cite news |last=O'Neill |first=Ian |url=http://news.discovery.com/space/astronomy/event-horizon-telescope-will-probe-spacetimes-mysteries-150702.htm |title=Event Horizon Telescope Will Probe Spacetime's Mysteries |work=Discovery News |date=2 July 2015 |access-date=2015-08-21 |archive-url=https://web.archive.org/web/20150905193743/http://news.discovery.com/space/astronomy/event-horizon-telescope-will-probe-spacetimes-mysteries-150702.htm |archive-date=September 5, 2015 |url-status=dead }} The effort includes development and deployment of submillimeter dual polarization receivers, highly stable frequency standards to enable very-long-baseline interferometry at 230–450 GHz, higher-bandwidth VLBI backends and recorders, as well as commissioning of new submillimeter VLBI sites.{{Cite web|url=https://www.haystack.mit.edu/ast/uvlbi/mm/eht.html|title=MIT Haystack Observatory: Astronomy Wideband VLBI Millimeter Wavelength|website=www.haystack.mit.edu}}

Each year since its first data capture in 2006, the EHT array has moved to add more observatories to its global network of radio telescopes. The first image of the Milky Way's supermassive black hole, Sagittarius A*, was expected to be produced from data taken in April 2017,{{cite news |last=Webb |first=Jonathan |url=https://www.bbc.com/news/science-environment-35258378 |title=Event horizon snapshot due in 2017 |work=BBC News|date=8 January 2016 |access-date=2016-03-24 }}{{cite journal|title=How to hunt for a black hole with a telescope the size of Earth|author=Davide Castelvecchi|journal=Nature|volume=543|issue=7646|pages=478–480|doi=10.1038/543478a|pmid=28332538|date=23 March 2017|bibcode = 2017Natur.543..478C |doi-access=free}} but because there are no flights in or out of the South Pole during austral winter (April to October), the full data set could not be processed until December 2017, when the shipment of data from the South Pole Telescope arrived.{{Cite web|url=http://eventhorizontelescope.org/blog/eht-status-update-december-15-2017|title=EHT Status Update, December 15 2017|website=eventhorizontelescope.org|date=December 15, 2017 |access-date=2018-02-09}}

Data collected on hard drives are transported by commercial freight airplanes{{Cite web|url=https://www.theatlantic.com/science/archive/2019/04/black-hole-hard-disks-picture/587119/|title=The Hidden Shipping and Handling Behind That Black-Hole Picture|website=The Atlantic|date=April 13, 2019 |language=en|access-date=2019-04-14}} (a so-called sneakernet) from the various telescopes to the MIT Haystack Observatory and the Max Planck Institute for Radio Astronomy, where the data are cross-correlated and analyzed on a grid computer made from about 800 CPUs all connected through a {{nowrap|40 Gbit/s}} network.{{cite news |last=Mearian |first=Lucas |url=http://www.computerworld.com/article/2972251/space-technology/massive-telescope-array-aims-for-black-hole-gets-gusher-of-data.html |title=Massive telescope array aims for black hole, gets gusher of data |work=Computerworld |date=18 August 2015 |access-date=2015-08-21 }}

Because of the COVID-19 pandemic, weather patterns, and celestial mechanics, the 2020 observational campaign was postponed to March 2021.{{Cite web|url=https://eventhorizontelescope.org/blog/eht-observing-campaign-2020-canceled-due-covid-19-outbreak|title=EHT Observing Campaign 2020 Canceled Due to the COVID-19 Outbreak|website=eventhorizontelescope.org|date=March 17, 2020 |language=en|access-date=2020-03-29}}

File:Event Horizon Telescope and Apollo 16.png

File:Black hole - Messier 87 crop max res.jpg generated from data gathered by the Event Horizon Telescope{{cite news |last=Overbye |first=Dennis |author-link=Dennis Overbye |title=Black Hole Picture Revealed for the First Time – Astronomers at last have captured an image of the darkest entities in the cosmos |url=https://www.nytimes.com/2019/04/10/science/black-hole-picture.html?comments#permid=31473598 |date=April 10, 2019 |work=The New York Times |access-date=April 10, 2019 }}{{cite news |last=Landau |first=Elizabeth |title=Black Hole Image Makes History |url=https://www.jpl.nasa.gov/news/news.php?feature=7372 |date=April 10, 2019 |work=NASA |access-date=April 10, 2019 }}]]

File:A view of the M87 supermassive black hole in polarised light.tif black hole in polarised light]]

The Event Horizon Telescope Collaboration announced its first results in six simultaneous press conferences worldwide on April 10, 2019.{{cite web|url=https://eventhorizontelescope.org/blog/media-advisory-first-results-event-horizon-telescope-be-presented-april-10th|title=Media Advisory: First Results from the Event Horizon Telescope to be Presented on April 10th|publisher=Event Horizon Telescope|date=1 April 2019|website=Event Horizon official blog|access-date=10 April 2019}} The announcement featured the first direct image of a black hole, which showed the supermassive black hole at the center of Messier 87, designated M87*.{{cite magazine |last=Lu |first=Donna |date=April 12, 2019 |title=How do you name a black hole? It is actually pretty complicated |url=https://www.newscientist.com/article/2199578-how-do-you-name-a-black-hole-it-is-actually-pretty-complicated/ |magazine=New Scientist |location=London |access-date=April 12, 2019 |quote=“For the case of M87*, which is the designation of this black hole, a (very nice) name has been proposed, but it has not received an official IAU approval,” says Christensen.}}{{cite news |last=Gardiner |first=Aidan |title=When a Black Hole Finally Reveals Itself, It Helps to Have Our Very Own Cosmic Reporter – Astronomers announced Wednesday that they had captured the first image of a black hole. The Times's Dennis Overbye answers readers' questions.|url=https://www.nytimes.com/2019/04/12/reader-center/black-holes-dennis-overbye.html |date=12 April 2018 |work=The New York Times|access-date=15 April 2019 }} The scientific results were presented in a series of six papers published in The Astrophysical Journal Letters.{{cite news|url=https://www.eso.org/public/news/eso1907/|title=Astronomers Capture First Image of a Black Hole|work=European Southern Observatory|date=10 April 2019|access-date=10 April 2019}} A clockwise rotating black hole was observed in the 6σ region.{{cite journal | doi=10.1093/mnrasl/slz176 | title=Measurement of the spin of the M87 black hole from its observed twisted light | year=2020 | last1=Tamburini | first1=Fabrizio | last2=Thidé | first2=Bo | last3=Della Valle | first3=Massimo | journal=Monthly Notices of the Royal Astronomical Society: Letters | volume=492 | pages=L22–L27 | doi-access=free | arxiv=1904.07923 }}

The image provided a test for Albert Einstein's general theory of relativity under extreme conditions. Studies have previously tested general relativity by looking at the motions of stars and gas clouds near the edge of a black hole. However, an image of a black hole brings observations even closer to the event horizon.{{cite news|url=https://www.sciencenews.org/article/black-hole-first-picture-event-horizon-telescope|title=The first picture of a black hole opens a new era of astrophysics|author=Lisa Grossman, Emily Conover|work=Science News|date=10 April 2019|access-date = 10 April 2019}} Relativity predicts a dark shadow-like region, caused by gravitational bending and capture of light, which matches the observed image. The published paper states: "Overall, the observed image is consistent with expectations for the shadow of a spinning Kerr black hole as predicted by general relativity."{{cite web|url=https://astronomy.com/news/2019/04/the-nature-of-m87-a-look-at-a-supermassive-black-hole|title=The nature of M87: EHT's look at a supermassive black hole|author=Jake Parks|website=Astronomy|date=10 April 2019|access-date=10 April 2019}} Paul T. P. Ho, EHT Board member, said: "Once we were sure we had imaged the shadow, we could compare our observations to extensive computer models that include the physics of warped space, superheated matter, and strong magnetic fields. Many of the features of the observed image match our theoretical understanding surprisingly well."

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. Previous observations of M87 showed that the large-scale 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°.{{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|bibcode = 2018ApJ...855..128W|s2cid = 59322635 | doi-access=free }} 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.{{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|access-date=10 April 2019}} 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 10⁴² erg/s via the Blandford–Znajek process.{{cite journal | bibcode=1977MNRAS.179..433B | title=Electromagnetic extraction of energy from Kerr black holes | last1=Blandford | first1=R. D. | last2=Znajek | first2=R. L. | journal=Monthly Notices of the Royal Astronomical Society | year=1977 | volume=179 | issue=3 | page=433 | doi=10.1093/mnras/179.3.433 | doi-access=free }}

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.{{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 |s2cid=146068771 |doi-access=free }} These methods included both an established algorithm in radio astronomy for image reconstruction known as CLEAN, invented by Jan Högbom,{{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}} as well as self-calibrating image processing methods{{cite journal | bibcode=1998A&A...337..325S | title=Entropy-regularized maximum-likelihood cluster mass reconstruction | last1=Seitz | first1=Stella | last2=Schneider | first2=Peter | last3=Bartelmann | first3=Matthias | journal=Astronomy and Astrophysics | year=1998 | volume=337 | page=325 | arxiv=astro-ph/9803038 }} for astronomy such as the CHIRP algorithm created by Katherine Bouman and others.{{Cite web|url=https://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|date=April 11, 2019|language=en-US|access-date=2019-04-15}} The algorithms that were ultimately used were a regularized maximum likelihood (RML){{cite journal | doi=10.1146/annurev.aa.24.090186.001015 | title=Maximum Entropy Image Restoration in Astronomy | year=1986 | last1=Narayan | first1=Ramesh | last2=Nityananda | first2=Rajaram | journal=Annual Review of Astronomy and Astrophysics | volume=24 | pages=127–170 | bibcode=1986ARA&A..24..127N }} algorithm and the CLEAN algorithm.

In March 2020, astronomers proposed an improved way of seeing more of the rings in the first black hole image.{{cite news |last=Overbye |first=Dennis |author-link=Dennis Overbye |title=Infinite Visions Were Hiding in the First Black Hole Image's Rings – Scientists proposed a technique that would allow us to see more of the unseeable. |url=https://www.nytimes.com/2020/03/28/science/black-hole-rings.html |date=28 March 2020 |work=The New York Times |access-date=29 March 2020 }}{{cite journal |author=Johnson, Michael D. |display-authors=et al. |title=Universal interferometric signatures of a black hole's photon ring |date=18 March 2020 |journal=Science Advances |volume=6 |issue=12, eaaz1310 |pages=eaaz1310 |doi=10.1126/sciadv.aaz1310 |pmid=32206723 |pmc=7080443 |arxiv=1907.04329 |bibcode=2020SciA....6.1310J |doi-access=free }} In March 2021, a new photo was revealed, showing how the M87 black hole looks in polarised light. This is the first time astronomers have been able to measure polarisation so close to the edge of a black hole. The lines on the photo mark the orientation of polarisation, which is related to the magnetic field around the shadow of the black hole.{{cite web |title=A view of the M87 supermassive black hole in polarised light |url=https://www.eso.org/public/images/eso2105a/ |publisher=ESO |access-date=24 March 2021}}

In August 2022, a team led by University of Waterloo researcher Avery Broderick released a "remaster[ed]" version of original image generated from the data collected by the EHT. This image "resolve[d] a fundamental signature of gravity around a black hole," with it showing a displaying photon ring around M87*.{{Cite web |date=2022-08-16 |title=The photon ring: a black hole ready for its close-up |url=https://uwaterloo.ca/news/media/photon-ring-black-hole-ready-its-close |access-date=2022-08-28 |website=Waterloo News |language=en}}{{Cite web |author1=Robert Lea |date=2022-08-17 |title=Supermassive black hole's bright 'photon ring' revealed in new image |url=https://www.space.com/supermassive-black-hole-photon-ring-image |access-date=2022-08-28 |website=Space.com |language=en}} The claim has been subsequently disputed.{{Cite web |date=2022-08-31 |title=Physicists dispute a claim of detecting a black hole's 'photon ring' |url=https://www.sciencenews.org/article/disputed-photon-ring-supermassive-black-hole-image-eht |access-date=2022-09-19 |website=Science News |language=en-US}}

In 2023, EHT released new, sharper images of the M87 black hole, reconstructed from the same 2017 data but created using the PRIMO algorithm.{{cite journal |last1=Medeiros |first1=Lia |last2=Psaltis |first2=Dimitrios |last3=Lauer |first3=Tod R. |last4=Özel |first4=Feryal |title=The Image of the M87 Black Hole Reconstructed with PRIMO |journal=The Astrophysical Journal Letters |date=1 April 2023 |volume=947 |issue=1 |pages=L7 |doi=10.3847/2041-8213/acc32d |arxiv=2304.06079 |bibcode=2023ApJ...947L...7M |s2cid=258108405 |doi-access=free }}

File:EHT3C279PressReleaseImage.png

In April 2020, the EHT released the first 20 microarcsecond resolution images of the archetypal blazar 3C 279 it observed in April 2017.{{Cite journal |title=Event Horizon Telescope imaging of the archetypal blazar 3C 279 at an extreme 20 microarcsecond resolution |first1=Jae-Young |last1=Kim |display-authors=et al. |date=April 5, 2020 |journal=Astronomy & Astrophysics |volume=640 |pages=A69 |doi=10.1051/0004-6361/202037493 |bibcode=2020A&A...640A..69K |doi-access=free |hdl=10261/227201 |hdl-access=free }} These images, generated from observations over 4 nights in April 2017, reveal bright components of a jet whose projection on the observer plane exhibit apparent superluminal motions with speeds up to 20 c.{{Cite web|url=https://eventhorizontelescope.org/blog/something-is-lurking-in-the-heart-of-quasar-3c-279|title= Something is Lurking in the Heart of Quasar 3C 279 |website=Event Horizon Telescope|language=en-US|access-date=2019-04-20}} Such apparent superluminal motion from relativistic emitters such as an approaching jet is explained by emission originating closer to the observer (downstream along the jet) catching up with emission originating further from the observer (at the jet base) as the jet propagates close to the speed of light at small angles to the line of sight.

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File:EHTcentaurusA2021.jpg

In July 2021, high resolution images of the jet produced by the supermassive black hole sitting at the center of Centaurus A were released. With a mass around {{Solar mass|{{val|5.5e7}}|link=yes}}, the black hole is not large enough for its photon sphere to be observed, as in EHT images of Messier M87*, but its jet extends even beyond its host galaxy while staying as a highly collimated beam which is a point of study. Edge-brightening of the jet was also observed which would exclude models of particle acceleration that are unable to reproduce this effect. The image was 16 times sharper than previous observations and utilized a 1.3 mm wavelength.{{Cite journal|last1=Janssen|first1=Michael|last2=Falcke|first2=Heino|last3=Kadler|first3=Matthias|last4=Ros|first4=Eduardo|last5=Wielgus|first5=Maciek|last6=Akiyama|first6=Kazunori|last7=Baloković|first7=Mislav|last8=Blackburn|first8=Lindy|last9=Bouman|first9=Katherine L.|last10=Chael|first10=Andrew|last11=Chan|first11=Chi-kwan|date=2021-07-19|title=Event Horizon Telescope observations of the jet launching and collimation in Centaurus A|journal=Nature Astronomy|volume=5|issue=10|language=en|pages=1017–1028|doi=10.1038/s41550-021-01417-w|arxiv=2111.03356 |bibcode=2021NatAs...5.1017J |issn=2397-3366|doi-access=free}}{{Cite journal|last=Gabuzda|first=Denise C.|date=2021-07-19|title=Peering into the heart of an active galaxy|journal=Nature Astronomy|volume=5|issue=10|language=en|pages=982–983|doi=10.1038/s41550-021-01420-1|bibcode=2021NatAs...5..982G |s2cid=237675257|issn=2397-3366}}{{Cite web|title=EHT Pinpoints Dark Heart of the Nearest Radio Galaxy|url=https://eventhorizontelescope.org/blog/eht-pinpoints-dark-heart-nearest-radio-galaxy|access-date=2021-07-20|website=eventhorizontelescope.org|date=19 July 2021 |language=en}}

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{{Multiple image

| image1 = EHT Saggitarius A black hole.tif

| caption1 = Sagittarius A*, first image released in 2022

| image2 = Sagittarius Astar in polarised light.tif

| caption2 = Sagittarius A* in polarised light, image released in 2024

| total_widths = 400

}}

On May 12, 2022, the EHT Collaboration revealed an image of Sagittarius A*, the supermassive black hole at the center of the Milky Way galaxy. The black hole is 27,000 light-years away from Earth; it is thousands of times smaller than M87*. Sera Markoff, Co-Chair of the EHT Science Council, said: "We have two completely different types of galaxies and two very different black hole masses, but close to the edge of these black holes they look amazingly similar. This tells us that General Relativity governs these objects up close, and any differences we see further away must be due to differences in the material that surrounds the black holes."{{cite web |title=Astronomers reveal first image of the black hole at the heart of our galaxy |url=https://www.eso.org/public/news/eso2208-eht-mw/ |website=www.eso.org |language=en}}

On March 22, 2024, the EHT Collaboration released an image of Sagittarius A* in polarized light.{{cite web |title=Astronomers unveil strong magnetic fields spiraling at the edge of Milky Way's central black hole |url=https://www.eso.org/public/news/eso2406/ |website=www.eso.org |access-date=27 March 2024 |language=en}}

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File:EHTj1924-2914.png

In August 2022, the EHT together with Global Millimeter VLBI Array and the Very Long Baseline Array imaged the distant blazar J1924-2914. They operated at 230 GHz, 86 GHz and 2.3+8.7 GHz, respectively, the highest angular resolution images of polarized emission from a quasar ever obtained. Observations reveal a helically bent jet and the polarization of its emission suggest a toroidal magnetic field structure. The object is used as calibrator for Sagittarius A* sharing strong optical variability and polarization with it.{{Cite journal |last1=Issaoun |first1=Sara |last2=Wielgus |first2=Maciek |last3=Jorstad |first3=Svetlana |last4=Krichbaum |first4=Thomas P. |last5=Blackburn |first5=Lindy |last6=Janssen |first6=Michael |last7=Chan |first7=Chi-kwan |last8=Pesce |first8=Dominic W. |last9=Gómez |first9=José L. |last10=Akiyama |first10=Kazunori |last11=Mościbrodzka |first11=Monika |last12=Martí-Vidal |first12=Iván |last13=Chael |first13=Andrew |last14=Lico |first14=Rocco |last15=Liu |first15=Jun |date=2022-08-01 |title=Resolving the Inner Parsec of the Blazar J1924–2914 with the Event Horizon Telescope |journal=The Astrophysical Journal |language=en |volume=934 |issue=2 |pages=145 |doi=10.3847/1538-4357/ac7a40 |arxiv=2208.01662 |bibcode=2022ApJ...934..145I |s2cid=251274752 |issn=0004-637X |doi-access=free }}{{Cite web |title=Resolving the core of the J1924-2914 blazar with the Event Horizon Telescope |url=https://eventhorizontelescope.org/blog/resolving-core-j1924-2914-blazar-event-horizon-telescope |access-date=2022-08-14 |website=eventhorizontelescope.org |date=6 August 2022 |language=en}}

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File:NRAO 530 by EHT 01.jpg

File:NRAO 530 by EHT 02.jpg

In February 2023, the EHT reported on the observations of the quasar NRAO 530. NRAO 530 (1730−130, J1733−1304) is a flat-spectrum radio quasar (FSRQ) that belongs to the class of bright γ-ray blazars and shows significant variability across the entire electromagnetic spectrum. The source was monitored by the University of Michigan Radio Observatory at 4.8, 8.4, and 14.5 GHz for several decades until 2012. The quasar underwent a dramatic radio outburst in 1997, during which its flux density at 14.5 GHz exceeded 10 Jy, while the average value is ~2 Jy. Since 2002, NRAO 530 has been monitored by the Submillimeter Array (SMA; Maunakea, Hawaii) at 1.3 mm and 870 μm. NRAO 530 has a redshift of z = 0.902 (Junkkarinen 1984), for which 100 μas corresponds to a linear distance of 0.803 pc. The source contains a supermassive black hole, the mass of which is currently uncertain, with estimates ranging from {{val|3e8}} M☉ to {{val|2e9}} M☉.{{cite journal |last1=Jorstad |first1=Svetlana |last2=Wielgus |first2=Maciek |last3=Lico |first3=Rocco |display-authors=1 |title=The Event Horizon Telescope Image of the Quasar NRAO 530 |journal=The Astrophysical Journal |date=1 February 2023 |volume=943 |issue=2 |pages=170 |doi=10.3847/1538-4357/acaea8 |arxiv=2302.04622 |bibcode=2023ApJ...943..170J |s2cid=256661718 |doi-access=free }} 50px Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/3.0/ Creative Commons Attribution 4.0]

It was observed with the Event Horizon Telescope on 2017 April 5−7, when NRAO 530 was used as a calibrator for the EHT observations of Sagittarius A*. The observations were performed with the full EHT 2017 array of eight telescopes located at six geographical sites. At z = 0.902, this is the most distant object imaged by the EHT so far. The team reconstructed the first images of the source at 230 GHz, at an angular resolution of ~20 μas, both in total intensity and in linear polarization (LP). Source variability was not detected, that allowed to represent the whole data set with static images. The images reveal a bright feature located on the southern end of the jet, which was associated with the core. The feature is linearly polarized, with a fractional polarization of ~5%–8%, and it has a substructure consisting of two components. Their observed brightness temperature suggests that the energy density of the jet is dominated by the magnetic field. The jet extends over 60 μas along a position angle ~ −28°. It includes two features with orthogonal directions of polarization (electric vector position angle), parallel and perpendicular to the jet axis, consistent with a helical structure of the magnetic field in the jet. The outermost feature has a particularly high degree of LP, suggestive of a nearly uniform magnetic field.

The EHT Collaboration consists of 13 stakeholder institutes:[http://eventhorizontelescope.org/organization Event Horizon Telescopoe, Organisation], EHT Website, accessed: 2022-01-30.

• the Academia Sinica Institute of Astronomy and Astrophysics
• the University of Arizona
• the University of Chicago
• the East Asian Observatory
• Goethe University Frankfurt
• Smithsonian Astrophysical Observatory (part of the Center for Astrophysics {{!}} Harvard & Smithsonian)
• Institut de radioastronomie millimétrique (IRAM, itself a collaboration between the French CNRS, the German Max Planck Society, and the Spanish Instituto Geográfico Nacional),
• Large Millimeter Telescope Alfonso Serrano
• Max Planck Institute for Radio Astronomy
• MIT Haystack Observatory
• National Astronomical Observatory of Japan
• Perimeter Institute for Theoretical Physics
• Radboud University

File:Locations of the telescopes that make up the EHT array (eso2208-eht-mwi).tiff

The EHT Collaboration receives funding from numerous sources including:{{Cite web |title=Funding Support |url=https://eventhorizontelescope.org/funding-support |access-date=2023-09-27 |website=eventhorizontelescope.org |language=en}}

• United States National Science Foundation
• European Research Council
• Ministry of Science and Technology of Taiwan
• Max-Planck-Gesellschaft
• Consejo Nacional de Ciencia y Technologia, Mexico
• John Templeton Foundation
• Gordon and Betty Moore Foundation
• Japan Society for the Promotion of Science
• Natural Sciences and Engineering Research Council of Canada
• Academia Sinica
• Smithsonian Institution

Additionally, Western Digital and Xilinx are industry donors.{{Cite web |title=Industry Donors |url=https://eventhorizontelescope.org/industry-donors |access-date=2023-09-27 |website=eventhorizontelescope.org |language=en}}

{{Reflist}}

{{Commons}}

• {{Official website}}
• [https://www.reddit.com/r/askscience/comments/olel36/askscience_ama_series_were_event_horizon_horizon/ EHT "Ask Me Anything" (AMA) serie] on reddit
• [https://www.ngeht.org/ The Next Generation Event Horizon Telescope]

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Category:Interferometric telescopes

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