Astronomers’ polarized image shows magnetic fields at the edge of M87’s black hole


In this artist’s conception of the polarized view of the black hole in M87, the lines mark the orientation of the polarization, which is related to the magnetic field around the black hole’s shadow. Credit: EHT Collaboration

The new image of M87 reveals what it looks like in polarized light.

MIT Haystack Observatory is one of 13 interested institutions that make up the Event Horizon Telescope (EHT) collaboration, which produced the first image of a dungeon. The EHT today revealed a new view of the massive object at the center of the galaxy M87: how it looks in polarized light. This is the first time that astronomers have been able to measure polarization, a signature of magnetic fields, so close to the edge of a black hole. The observations are key to explaining how the galaxy M87, located 55 million light years away, is capable of launching jets of energy from its core.

Haystack Research Scientist Vincent Fish says: “Hundreds of people around the world in the EHT collaboration, including Haystack scientists and engineers, have worked very hard to investigate the role of magnetic fields in the formation of jets around the black holes. Can magnetic fields build up and overpower the intense pull of gravity? Our data provides an answer. “

On April 10, 2019, scientists published the first image of a black hole, revealing a bright ring-shaped structure with a dark central region – the black hole’s shadow. Since then, the EHT collaboration has delved into data on the supermassive object at the heart of the galaxy M87 collected in 2017. They have revealed that the famous ring of light at the edge of the black hole M87 was polarized across the ring.

“Astronomers have obtained a new tool to study the magnetism of a black hole with direct images of the polarization of light,” explains Kazunori Akiyama, coordinator of the EHT Imaging Working Group and research scientist at the Haystack Observatory. “This remarkable feat of the Event Horizon Telescope was truly accomplished by years of international efforts to develop state-of-the-art techniques at every stage of complex signal processing, from telescopes to imaging.”

Jet M87 and supermassive black hole

An artist’s composite display of M87 and ring in polarization. Credit: Image created by JC Algaba and I. Marti-Vidal.

Light becomes polarized when it passes through certain filters, such as polarized sunglasses lenses, or when it is emitted in warm regions of space that are magnetized. In the same way that polarized sunglasses only transmit a specific orientation of the electric field of light rays from the sun, astronomers can obtain information about the orientation of the electric field of light coming from outer space, using polarizers installed in their telescopes. Specifically, polarization allows astronomers to map the magnetic field lines present at the inner edge of the black hole.

“Polarization is a powerful tool available to astronomers to probe physical conditions in one of the most extreme environments in the universe. It can provide clues not only to the strength and orientation of magnetic fields, but also to how well ordered those fields are, and possibly even something about the otherwise invisible material that lies between us and the material. which emits radio waves, ”says Colin. Lonsdale, director of MIT’s Haystack Observatory and Chairman of the Board of Event Horizon Telescope.

The bright jets of energy and matter emerging from the core of M87 and extending at least 5,000 light-years from its center are one of the most mysterious and energetic features of the galaxy. Most of the matter near the edge of a black hole falls. However, some of the surrounding particles escape moments before capture and are expelled 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, or exactly how matter falls into the black hole. With the new EHT image of the black hole and its shadow in polarized light, astronomers were able for the first time to look into the region just outside the black hole, where this interaction between inward-flowing matter and ejection is occurring.

The observations provide new information about the structure of the magnetic fields just outside the black hole. The team found that only theoretical models with strongly magnetized gas can explain what they are seeing on the event horizon.

“New polarization images suggest that the powerful jet is made up of plasma flow stopped by magnetic fields aligned in the vicinity of the black hole, resisting its strong gravitational pull, ”explains Kotaro Moriyama, an overseas postdoctoral fellow at the Japan Society for the Promotion of Science at the Haystack Observatory.

To observe the heart of the M87 galaxy, the collaboration linked eight telescopes from around the world, including SOUL (Atacama Large Millimeter / submillimeter Array) and APEX (Atacama Pathfinder Experiment) in northern Chile, to create a virtual Earth-size telescope, the EHT. The impressive resolution obtained with the EHT is equivalent to that required to measure the length of a credit card on the surface of the moon.

“ALMA plays a central role in the whole process – it has a central location to tie the EHT array together and it is also the most sensitive telescope in the array, so getting the most out of the EHT data is crucial,” says Geoff Crew, Scientist. Haystack researcher. “Additionally, years of work on ALMA’s polarimetry analysis have provided much more than we imagined.”


The Event Horizon Telescope (EHT) collaboration, which produced the first image of a black hole, today revealed a new view of the massive object at the center of the Messier 87 galaxy: how it looks in polarized light. This is the first time that astronomers have been able to measure polarization, a signature of magnetic fields, so close to the edge of a black hole. This video summarizes the discovery.

This resolution allowed the team to directly observe the black hole’s shadow and the ring of light around it, with the new polarized light image clearly showing that the ring is magnetized. The results are published today in two separate articles in The Astrophysical Journal Letters for the EHT collaboration. The research involved more than 300 researchers from multiple organizations and universities around the world.

A third article, “Polarimetric Properties of ALMA Event Horizon Telescope Objectives”, was also published in the Astrophysical journal letters, led by Ciriaco Goddi, a scientist at Radboud University and Leiden Observatory, the Netherlands, which includes Haystack research scientists Geoff Crew and Lynn Matthews, and is based on data from ALMA.

Goddi says: “The ALMA data was acquired simultaneously with the VLBI observations made in April 2017 with the EHT (and GMVA); in this sense, they are a ‘by-product’ of VLBI operations. The ALMA data was crucial in calibrating, imaging, and interpreting the EHT polarization observations, providing strict constraints to the theoretical models that explain how matter behaves near the black hole’s event horizon. These data also provide a description of the structure of the magnetic field along the powerful relativistic jets that extend far beyond the M87 galaxy. The combined information from the EHT and ALMA allows scientists to investigate the role of magnetic fields from the vicinity of the event horizon to well beyond the M87 galaxy along its powerful relativistic jets (on scales of thousands of light years). ”.

Crew adds, “ALMA bridges the resolution gap between the ultra-high resolution of VLBI arrays and that obtained with other measurement techniques. In combination, this wealth of new polarimetry data should allow us to advance our understanding of this fascinating object. “

More about this research:

References:

“Results of the first Event Horizon M87 telescope. VII. Ring Polarization ”by The Event Horizon Telescope Collaboration, Kazunori Akiyama, Juan Carlos Algaba, Antxon Alberdi, Walter Alef, Richard Anantua, Keiichi Asada, Rebecca Azulay, Anne-Kathrin Baczko, David Ball, et al., March 24, 2021 , Astrophysical journal letters.
DOI: 10.3847 / 2041-8213 / abe71d

“Results of the first Event Horizon M87 telescope. VIII. Magnetic Field Structure Near The Event Horizon ”by The Event Horizon Telescope Collaboration, Kazunori Akiyama, Juan Carlos Algaba, Antxon Alberdi, Walter Alef, Richard Anantua, Keiichi Asada, Rebecca Azulay, Anne-Kathrin Baczko, David Ball, et al. , March 24, 2021, Astrophysical journal letters.
DOI: 10.3847 / 2041-8213 / abe4de

“Polarimetric properties of ALMA Event Horizon Telescope targets” by Ciriaco Goddi, Iván Martí-Vidal, Hugo Messias, Geoffrey C. Bower, Avery E. Broderick, Jason Dexter, Daniel P. Marrone, Monika Moscibrodzka, Hiroshi Nagai, Juan Carlos Algaba, et al., March 24, 2021, Astrophysical journal letters.
DOI: 10.3847 / 2041-8213 / abee6a

More information

The EHT collaboration involves more than 300 researchers from Africa, Asia, Europe, and North and South America. The international collaboration is working to capture the most detailed black hole images ever obtained by creating a virtual telescope the size of Earth. Backed by considerable international investment, the EHT connects existing telescopes using novel systems, creating a fundamentally new instrument with the highest angular resolving power ever achieved.

The individual telescopes involved are ALMA, APEX, the IRAM 30-meter telescope, the IRAM NOEMA observatory, the James Clerk Maxwell telescope, the large millimeter telescope, the submillimeter matrix, the submillimeter telescope, the South Pole telescope, the Kitt Peak telescope. , and the Greenland Telescope.

The EHT consortium is made up of 13 interested institutes: the Academia Sinica Institute for Astronomy and Astrophysics, the University of Arizona, the University of Chicago, the East Asia Observatory, Goethe-Universitaet Frankfurt, Institut de Radioastronomie Millimétrique, Large Millimeter Telescope, Max Planck Institute for Radio Astronomy, MIT Haystack Observatory, Japan National Astronomical Observatory, Perimeter Institute for Theoretical Physics, Radboud University, and Smithsonian Astrophysical Observatory.

This article is adapted from an advertisement for the Event Horizon Telescope.



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