From Max Planck Institute for Radio Astronomy: “The ring around the black hole glitters”

From Max Planck Institute for Radio Astronomy

September 23, 2020

Dr. Norbert Junkes
Press and public relations
Max Planck Institute for Radio Astronomy, Bonn
+49 2 28525-399

Prof. Dr. J. Anton Zensus
Max Planck Institute for Radio Astronomy, Bonn
+49 228 525-378

Astronomers of the Event Horizon Telescope conclude from archive data how the surroundings of the mass monster in the galaxy M 87 have changed.

In the center of the giant galaxy Messier 87 lurks a giant black hole.

Messier 87*, The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

The image of this mass monster published last year and obtained with the Event Horizon Telescope (EHT) went around the world.

EHT map

Now the EHT team has analyzed archive data from 2009 to 2013, some of which are still unpublished. The researchers found that the ring-shaped shadow around the black hole is indeed always present, but changes its orientation and brightness distribution – the ring seems to be glittering. The participation of the European APEX telescope in Chile and the IRAM 30-meter telescope co-financed by the Max Planck Society on Pico Veleta in the Spanish Sierra Nevada played an important part in this discovery.

ESO/MPIfR APEX high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft).

IRAM 30m Radio telescope, on Pico Veleta in the Spanish Sierra Nevada,, Altitude 2,850 m (9,350 ft).

Snapshots of the M 87* black hole obtained through imaging / geometric modeling, and the EHT array of telescopes in 2009 – 2017. The diameter of all rings is similar, but the location of the bright side varies. The variation of the thickness of the ring is most likely not real and results from the limited number of participating observatories in earlier experiments. © M. Wielgus, D. Pesce & EHT Collaboration.

“The results announced in April 2019 show an image of the shadow of a black hole, consisting of a bright ring formed by hot plasma swirling around the black hole in Messier 87, and a dark central part, where we expect the event horizon to be”, reminds Maciek Wielgus, astronomer at Harvard University, and lead author of the new paper.

However, those results were based only on observations performed throughout a one-week long time window in April 2017, which is far too short to see if the ring is evolving over longer time scales. Even after careful data analysis, therefore some open questions with regard to the stationarity of the ring features over time remained. For that reason, an investigation of earlier archival data was considered.

The 2009 – 2013 observations consist of far less data than the ones performed in 2017, making it hard to image Messier 87 without a-priori assumptions. For the available archive data, the EHT team used statistical modeling based on geometrical assumptions to look at changes in the appearance of the black hole in M 87 (M 87*) over time.

Expanding the analysis to the 2009-2017 observations, scientists have shown that Messier 87* adheres to theoretical expectations. The black hole’s shadow diameter has remained consistent with the prediction of Einstein’s theory of general relativity for a black hole of 6.5 billion solar masses. The morphology of an asymmetric ring persists on timescales of several years, in a consistent manner which provides additional confidence about the nature of M 87* and the origin of its shadow.

But while the diameter of the ring remained constant over time, the EHT team found that the data were hiding a surprise. Thomas Krichbaum, astronomer at the Max Planck Institute for Radio Astronomy and one of the leading authors of the publication, says: “The data analysis suggests that the orientation and fine structure of the ring varies with time. This gives a first impression on the dynamical structure of the accretion flow, which surrounds the event horizon”. He adds: “Studying this region will be crucial for a better understanding of how black holes accrete matter and launch relativistic jets.”

The gas falling onto a black hole heats up to billions of degrees, ionizes and becomes turbulent in the presence of magnetic fields. Since the flow of matter is turbulent, the ring brightness appears to glittering with time, which challenges some theoretical models of accretion.

“The monitoring of the time variable structure of Messier 87 with the EHT is a challenge that will keep us busy over the next few years,” says Anton Zensus, Director at the Max Planck Institute for Radio Astronomy and Founding Chairman of the EHT Collaboration Board. „We are working in the analysis of the 2018 data, and preparing newer observations in 2021, with the addition of new sites such as the NOEMA Observatory in France, the most powerful radio telescope of its kind in the Northern Hemisphere and also co-financed by the Max-Plack-Gesellschaft as well as the Greenland Telescope, and Kitt Peak in Arizona,” adds Zensus.

IRAM NOEMA in the French Alps on the wide and isolated Plateau de Bure at an elevation of 2550 meters, the telescope currently consists of ten antennas, each 15 meters in diameter.interferometer, Located in the French Alpes on the wide and isolated Plateau de Bure at an elevation of 2550 meters.

NSF CfA Greenland telescope, at the Summit Station research camp, located at the highest point of the Greenland ice sheet at an altitude of 3,210 meters (10,530 feet).

ARO 12m Radio Telescope, Kitt Peak National Observatory, In the Arizona-Sonoran Desert on the Tohono O’odham Nation Arizona USA, Altitude 1,914 m (6,280 ft).

The enhanced imaging capabilities provided by this extended array will provide a more detailed view on the shadow of the black hole Messier 87* and on the innermost jet of the Messier 87 radio galaxy.

Science paper:
Monitoring the Morphology of M87* in 2009–2017 with the Event Horizon Telescope
The Astrophysical Journal

Cosmic twinkling. An animation representing one year of Messier 87* image evolution according to numerical simulations. Measured position angle is shown along with a 42 microarcsecond ring. For a part of the animation, image blurred to the EHT resolution is shown. © G. Wong, B. Prather, Ch. Gammie, M. Wielgus & EHT Collaboration.

See the full article here .
See also the full article from MIT Haystack here.


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The Max Planck Institute for Radio Astronomy (German: Max-Planck-Institut für Radioastronomie) is located in Bonn, Germany. It is one of 80 institutes in the Max Planck Society.

By combining the already existing radio astronomy faculty of the University of Bonn led by Otto Hachenberg with the new Max Planck institute the Max Planck Institute for Radio Astronomy was formed. In 1972 the 100-m radio telescope in Effelsberg was opened. The institute building was enlarged in 1983 and 2002.

The institute was founded in 1966 by the Max-Planck-Gesellschaft as the “Max-Planck-Institut für Radioastronomie” (MPIfR).

The foundation of the institute was closely linked to plans in the German astronomical community to construct a competitive large radio telescope in (then) West Germany. In 1964, Professors Friedrich Becker, Wolfgang Priester and Otto Hachenberg of the Astronomische Institute der Universität Bonn submitted a proposal to the Stiftung Volkswagenwerk for the construction of a large fully steerable radio telescope.

In the same year the Stiftung Volkswagenwerk approved the funding of the telescope project but with the condition that an organization should be found, which would guarantee the operations. It was clear that the operation of such a large instrument was well beyond the possibilities of a single university institute.

Already in 1965 the Max-Planck-Gesellschaft (MPG) decided in principle to found the Max-Planck-Institut für Radioastronomie. Eventually, after a series of discussions, the institute was officially founded in 1966.

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