11 telescopes around the world combined to research the core of a galaxy 55 million light-years away
Scientists of the Event Horizon Telescope (EHT) collaboration - among them astrophysicist Luciano Rezzolla and his team from Goethe University Frankfurt - have revealed today a new view of the massive object at the centre of the M87 galaxy: how it looks in polarised light. This is the first time astronomers have been able to measure polarisation, a signature of magnetic fields, this close to the edge of a black hole. The observations are key to explaining how the M87 galaxy, located 55 million light-years away, is able to launch energetic jets from its core – jets, that are about one million light years large.
FRANKFURT. Luciano Rezzolla, Professor of Theoretical Astrophysics at Goethe University Frankfurt, says: “Understanding what powers relativistic jets in galaxies is a long-standing open question in astrophysics. The jets in M87 are enormous and they would cover 10 per cent of our galaxy, for example. The challenging observations from the ETH telescopes, combined with the theoretical simulations carried out in Frankfurt, are now providing essential information on comparatively small length-scales: For the first time we are looking at what the magnetic field looks like that close to the black hole.
“We are now seeing the next crucial piece of evidence to understand how magnetic fields behave around black holes, and how activity in this very compact region of space can drive powerful jets that extend far beyond the galaxy," says Monika Moscibrodzka, Coordinator of the EHT Polarimetry Working Group and Assistant Professor at Radboud University in the Netherlands.
On 10 April 2019, scientists released the first ever image of a black hole, revealing a bright ring-like structure with a dark central region — the black hole's shadow. Since then, the EHT collaboration has delved deeper into the data on the supermassive object at the heart of the M87 galaxy collected in 2017. They have discovered that a significant fraction of the light around the M87 black hole is polarised.
“This work is a major milestone: the polarisation of light carries information that allows us to better understand the physics behind the image we saw in April 2019, which was not possible before," explains Iván Martí-Vidal, also Coordinator of the EHT Polarimetry Working Group and GenT Distinguished Researcher at the University of Valencia, Spain. He adds that “unveiling this new polarised-light image required years of work due to the complex techniques involved in obtaining and analysing the data."
Light becomes polarised when it goes through certain filters, like the lenses of polarised sunglasses, or when it is emitted in hot regions of space that are magnetised. In the same way polarised sunglasses help us see better by reducing reflections and glare from bright surfaces, astronomers can sharpen their vision of the region around the black hole by looking at how the light originating from there is polarised. Specifically, polarisation allows astronomers to map the magnetic field lines present at the inner edge of the black hole.
“The newly published polarised images are key to understanding how the magnetic field allows the black hole to 'eat' matter and launch powerful jets," says EHT collaboration member Andrew Chael, a NASA Hubble Fellow at the Princeton Center for Theoretical Science and the Princeton Gravity Initiative in the US.
The bright jets of energy and matter that emerge from M87's core and extend at least 5000 light-years from its centre are one of the galaxy's most mysterious and energetic features. Most matter lying close to the edge of a black hole falls in. However, some of the surrounding particles escape moments before capture and are blown far out into space in the form of jets.
Astronomers have relied on different models of how matter behaves near the black hole to better understand this process. But they still don't know exactly how jets larger than the galaxy are launched from its central region, which is as small in size as the Solar System, nor how exactly matter falls into the black hole. With the new EHT image of the black hole and its shadow in polarised light, astronomers managed for the first time to look into the region just outside the black hole where this interplay between matter flowing in and being ejected out is happening.
The observations provide new information about the structure of the magnetic fields just outside the black hole. The team found that only theoretical models featuring strongly magnetised gas can explain what they are seeing at the event horizon.
“The observations suggest that the magnetic fields at the black hole's edge are strong enough to push back on the hot gas and help it resist gravity's pull. Only the gas that slips through the field can spiral inwards to the event horizon," explains Jason Dexter, Assistant Professor at the University of Colorado Boulder, US, and coordinator of the EHT Theory Working Group.
To observe the heart of the M87 galaxy, the collaboration linked eight telescopes around the world, to create a virtual Earth-sized telescope, the EHT. The impressive resolution obtained with the EHT is equivalent to that needed to measure the length of a credit card on the surface of the Moon.
This allowed the team to directly observe the black hole shadow and the ring of light around it, with the new polarised-light image clearly showing that the ring is magnetised. The results are published today in two separate papers in The Astrophysical Journal Letters by the EHT collaboration. The research involved over 300 researchers from multiple organisations and universities worldwide.
"The EHT is making rapid advancements, with technological upgrades being done to the network and new observatories being added. We expect future EHT observations to reveal more accurately the magnetic field structure around the black hole and to tell us more about the physics of the hot gas in this region," concludes EHT collaboration member Jongho Park, an East Asian Core Observatories Association Fellow at the Academia Sinica, Institute of Astronomy and Astrophysics in Taipei.
The Event Horizon Collaboration, Kazunori Akiyama et al.: First M87 Event Horizon Telescope Results VII: polarization of the ring. Astrophysical Journal Letters, 910, L12 (2021) DOI 10.3847/2041-8213/abe71d (ApJL 910, L12)
The Event Horizon Collaboration: Kazunori Akiyama et al.: First M87 Event Horizon Telescope Results VIII: Magnetic Field Structure Near The Event Horizon. Astrophysical Journal Letters, 910, L13 (2021) DOI 10.3847/2041-8213/abe4de (ApJL 910, L13)
A view of the M87 supermassive black hole in polarised light: The Event Horizon Telescope (EHT) collaboration, who produced the first ever image of a black hole released in 2019, has today a new view of the massive object at the centre of the Messier 87 (M87) galaxy: how it looks in polarised light. This is the first time astronomers have been able to measure polarisation, a signature of magnetic fields, this close to the edge of a black hole. This image shows the polarised view of the black hole in M87. The lines mark the orientation of polarisation, which is related to the magnetic field around the shadow of the black hole.
Credit: EHT Collaboration
http://www.uni-frankfurt.de/99324167 (Animated GIF - Download)
Observation and Theory Image: Transition animation showing the observed polarization image and a best-fit theory image. Credit: S. Issaoun, M. Mościbrodzka with Polarimetry WG and OWG
Zoom into the heart of galaxy M87 – The video starts with a view on the ALMA telescope which is part of the Event Horizon Telescope, and zooms into the heart of galaxy M87. In the core, the first image of a black hole can be seen, the picture was produced in 2019. Then the new image follows which shows the supermassive object in polarised light. It is the first time that astronomers could detect polarisation as a signature of magnetic fields so closely to the event horizon of a black hole. Credit: ESO/L. Calçada, Digitized Sky Survey 2, ESA/Hubble, RadioAstron, De Gasperin et al., Kim et al., EHT Collaboration. Music: Niklas Falcke
Polarized Light: Light is an oscillating electromagnetic wave. If the waves have a preferred direction of oscillation, they are polarized. In space, moving hot gas, or 'plasma', threaded by a magnetic field emits polarized light. The polarized light rays that manage to escape the pull of the black hole travel to a distant camera. The intensity of the light rays and their direction are what EHT collaboration observes with the Event Horizon Telescope.
Credit: © EHT Collaboration and Fiks Film
Black holes are enveloped in plasma. This plasma has magnetic fields—areas where magnetism affects how matter moves—threaded throughout. As the magnetic field grows stronger, it changes shape and the polarized light EHT collaboration measures exhibits different patterns.
Credit: © EHT Collaboration and Crazybridge Studios
http://www.uni-frankfurt.de/99324248 (Image - Download)
View of the M87 supermassive black hole and jet in polarised light. This composite image shows three views of the central region of the Messier 87 (M87) galaxy in polarised light. The galaxy has a supermassive black hole at its centre and is famous for its jets that extend far beyond the galaxy. One of the polarised-light images, obtained with the Chile-based Atacama Large Millimeter/submillimeter Array (ALMA), shows part of the jet in polarised light, with a size of 6000 light years from the centre of the galaxy. The other polarised light images zoom in closer to the supermassive black hole: the middle view covers a region about one light year in size and was obtained with the National Radio Astronomy Observatory's Very Long Baseline Array (VLBA) in the US. The most zoomed-in view was obtained by linking eight telescopes around the world to create a virtual Earth-sized telescope, the Event Horizon Telescope or EHT. This allows astronomers to see very close to the supermassive black hole, into the region where the jets are launched. The lines mark the orientation of polarisation, which is related to the magnetic field in the regions imaged. The ALMA data provides a description of the magnetic field structure along the jet. Therefore the combined information from the EHT and ALMA allows astronomers to investigate the role of magnetic fields from the vicinity of the event horizon (as probed with the EHT on light-day scales) to far beyond the M87 galaxy along its powerful jets (as probed with ALMA on scales of thousands of light-years). The values in GHz refer to the frequencies of light at which the different observations were made. The horizontal lines show the scale (in light years) of each of the individual images. Credit: EHT Collaboration; ALMA (ESO/NAOJ/NRAO), Goddi et al.; VLBA (NRAO), Kravchenko et al.; J. C. Algaba, I. Martí-Vidal
Prof. Dr. Luciano Rezzolla
Chair of Theoretical Astrophysics
Institute for Theoretical Physics
Goethe University Frankfurt
Phone: +49 69 798-47871 / 47879
A research team from the universities of Frankfurt and Mainz shines a light on new global players in Africa and Asia.
When Korean pop bands such as boy group BTS reach millions of fans worldwide, and when films and music from Nigeria are seen and heard across the globe: What does this mean for the production of culture? And how does it affect our perception of cultural spaces? An interdisciplinary research team that brings together Economics, African Studies, Korean Studies, Sinology, Cultural Anthropology and Film Studies will look for answers to these questions at Goethe University Frankfurt and Johannes Gutenberg University Mainz over the next three years. With € 2.1 million in funding from Germany's Federal Ministry of Education and Research (BMBF), CEDITRAA (“Cultural Entrepreneurship and Digital Transformation in Africa and Asia") will study the emergence of what Pakistani writer Fatima Bhutto calls the “new world order of cultural production", which Hollywood and Europe no longer dominate.
FRANKFURT. In the early 1990s, Kenneth Nnebue, a Nigerian seller of home video equipment, picked up his VHS camera and changed the course of film history. To boost sales of VHS recorders, he produced his own film. “Living in Bondage" sold around 750,000 copies and spawned numerous imitations. Practically out of nowhere, Nigeria built up a film industry with global outreach, now popularly known as “Nollywood", which today ranks second only to India in terms of annual film output. “The rise of Nigeria and the global success of Korean films, TV dramas and pop music in the new millennium show that a fundamental shift is taking place in cultural production and reception across the globe," says Vinzenz Hediger, project leader and professor of cinema studies at Goethe University.
Digitalisation is one of the driving forces behind this transformation and the emergence of the “new world order of cultural production". The researchers in Frankfurt and Mainz will study how cultural industries with transregional audiences contribute to the economic growth and soft power of their regions and countries of origin. They will also examine the role of regional resources in the creative work of artists in music and film. “One open question," says economics professor Cornelia Storz, “is whether entrepreneurs in digital industries may, in fact, be more dependent on local resources than their global reach and outlook might suggest." Particular attention will be paid to how producers in music and film draw on cultural heritage to produce innovative formats which resonate with larger, global contexts.
The CEDITRAA research group will address these issues through a series of case studies on music and film in Africa and Asia. Here, the Archiv der Musik Afrikas (AMA), the Archive for the Music of Africa, at Johannes Gutenberg University Mainz will play a particularly important role. For the case studies dedicated to music and copyright issues, the AMA is an invaluable resource – particularly for research on “Afrobeats" and other forms of sub-Saharan pop music, which recombines different gernes in innovative new ways. “This music has many fans in the Global North as well," says Matthias Krings, professor of cultural anthropology and the popular culture of Africa in Mainz. “Among them is Beyoncé, who created a sensation with her 2020 album 'Black Is King', not least because it featured guest appearances by Afrobeats stars such as Burna Boy, Wizkid, Tiwa Savage and Yemi Alade."
The parts of the project dedicated to Asia will study the circulation and reception of Korean popular culture in Asia and Africa and benefit from close collaboration with non-university partners such as the Korean Film Archive. The case study dedicated to Taiwan will focus on the Kaohsiung Film Festival and its close ties to the Korean film industry. In Nigeria, the project will collaborate closely with the Nollywood Studies Centre at the Pan-Atlantic University in Lagos, a research institute with closes ties to the film and music industries in Nigeria. The Nigerian part of the project will include a PhD position at the Pan-Atlantic University.
Funded by Germany's Federal Ministry of Education and Research, the project will bring together for the first time the area studies research centres in the Rhine-Main University Alliance in a joint research initiative – the Centre for Interdisciplinary African Studies (ZIAF) and the Interdisciplinary Centre for East Asian Studies (IZO) at Goethe University and the Centre for Intercultural Studies (ZIS) at Johannes Gutenberg University Mainz.
The research project enhances the profile of area studies in the Rhine-Main University Alliance through its close connection to teaching. Project results will be used in teaching in several degree programmes, most notably the bachelor's degree programme “African Languages, Media, and Culture", which is being prepared as a joint programme of Goethe University Frankfurt and Johannes Gutenberg University Mainz.
Caption: Global popstars with an army of Twitter fans: K-pop superstars BTS (c) Kim-Hee Chu / dpa
Professor Vinzenz Hediger, Professor of Cinema Studies, Goethe University: firstname.lastname@example.org
Professor Claudia Storz, Chair for the Study of Economic Institutions, Innovation and East Asian Development, Goethe University: email@example.com
Professor Matthias Krings, Professor of Anthropology and Popular Culture of Africa, Johannes Gutenberg University Mainz: firstname.lastname@example.org