A supermassive black hole revealed in a cosmic dust cloud

  • Research
Published on April 26, 2022 Updated on April 29, 2022

on the February 16, 2022


An international team of researchers has unveiled the position of the supermassive black hole in the heart of the galaxy Messier 77 (M77). This work was possible due to the MATISSE instrument, built in France for the Very Large Telescope Interferometer (VLTI) at the European Southern Observatory (ESO). The international team, led by the Leiden Observatory, the Lagrange laboratory (CNRS–UCA–OCA) and the Côte d'Azur Observatory, carried out a thermal mapping of the dust in the heart of M77, making it possible to find the supermassive black hole hidden there.

Active galactic nuclei are the brightest compact sources in the Universe. In their center, a black hole of a few million to several billion solar masses attracts, compresses and superheats matter in the center of the galaxy. The enormous luminous energy dissipated and the dust winds it generates influence the global evolution of the galaxy and the formation of stars within it. The black hole is a destroyer but is also a creator, whose mysteries are closely related to the evolution of the Universe. 

 Throughout the second half of the 20th century, Seyfert galaxies, quasars, blazars and other radio galaxies were a great astrophysical enigma. Then a unified model showed that all these objects are active galaxies, dominated by the same global mechanism. A central black hole and its accretion disc – the active nucleus of the galaxy – is surrounded by a torus of dense dust. The different classes of object observed can be explained by the angle at which they are viewed from the Earth. Viewed face-on, they show the characteristic radiation of the active nucleus while seen edge-on this radiation is masked by the dust torus. 

The unified model has recently been called into question. However, the new MATISSE data of galaxy M77 (also called NGC1068), published today in the journal Nature, confirm it. The image obtained is of unparalleled resolution and reveals the torus of dust in the center of the galaxy surrounding the black hole. MATISSE's images combined with radio telescope data make it possible to locate where the black hole is hidden. 

 This result therefore reorients the fundamental scientific debate on the unified model of active galactic nuclei! 


 Galaxy M77 and the brand new image of its active nucleus.  This image is composite, with the hottest parts in blue and the coolest parts in red. The dotted ellipses indicate the position of the dust torus, slightly inclined towards the observer, which masks the black hole and obscures the light emitted in the southwest quadrant (bottom right) Note: the image on the right is taken from the Nature article. 

galaxie 2
galaxie 2

 An artist's view of the heart of M77. The energy source is a supermassive black hole in the center. It is surrounded by an accretion disc which is itself surrounded by a torus of gas and dust. In the case of M77, this torus masks the immediate environment of the black hole and reveals the dust wind. This illustration also shows relativistic jets observed by other means.

MATISSE is an instrument made available to all astronomers on the Very Large European Interferometer. It combines the four 8.2 m telescopes into one infrared "super telescope", the largest in the world. 
 The optical interferometry technique was developed at the Nice Observatory 46 years ago by Antoine Labeyrie. 

MATISSE was created by an international consortium of more than a hundred people led by the Joint Research Unit (UMR) Joseph-Louis Lagrange (CNRS, Université Côte d'Azur, Côte d'Azur Observatory) and supported by the National Institute for Earth Sciences and Astronomy (INSU–CNRS). 

 The Lagrange team (CNRS, UCA, OCA) consists of 8 researchers (including 4 CNRS) and 12 engineers (including 7 CNRS). Beyond their contribution to the design, production and development of MATISSE, Romain Petrov (Senior Researcher, CNRS), James Leftley (Postdoc, UCA), Florentin Millour (Assistant Astronomer, OCA), Anthony Meilland (Researcher, CNRS) and Bruno Lopez (Astronomer, OCA) played a special role in the complex investigation that solved the puzzle of the M77 observations, along with our Dutch colleagues from the Leiden Observatory who were in charge of this research program within the MATISSE consortium. Romain Petrov and Anthony Meilland processed the N-band data and validated their calibration, and Florentin Millour carried out the first image reconstruction, which overcame the problem of model-fitting based on too simple a geometry. James Leftley validated the reconstructed images and their interpretation by an independent approach and Bruno Lopez contributed the decisive idea on the dust composition which enabled the conversion of the images into temperature maps, produced by Violeta Gamez, Jacob Isbell (MPIA Heidelberg) and James Leftley. Romain Petrov, Walter Jaffe and Violeta Gamez (PhD student and first author of this article) were then able to show that the description of the dust actually supported the unified model of AGNs. 

We would like to take the opportunity of this ESO press release on a major MATISSE result to highlight the work of the UMR Lagrange team that led and coordinated the international consortium that designed and produced this instrument, which is now harvesting its first crop of major scientific breakthroughs. 

MATISSE's team was led by Bruno Lopez (Astronomer, OCA, PI), Romain Petrov (Senior Researcher, CNRS, Instrument Scientist, concept and commissioning), Pierre Antonelli (Research Officer, UNS, Project Manager, retired in 2018) and Stéphane Lagarde (System Engineer then Project Manager), with Philippe Berio (Research Officer, CNRS) and Florentin Millour (Assistant Astronomer, OCA), heads of data processing and image reconstruction software, Anthony Meilland (Researcher, CNRS, real-time processing), Alexis Matter (Assistant Astronomer, OCA, performance evaluation and ‘exposure time calculator’), Pierre Cruzalèbes (Researcher, CNRS, commissioning and calibration), Sylvie Robbe-Dubois (Associate Professor, UNS, optomechanics and integration), Fatmé Allouche (Project Engineer, UNS, guiding and data processing), Yves Bresson (Project Engineer, CNRS, optical analysis), Christophe Bailet (Project Engineer, UNS, mechanical analysis), Jean-Michel Clausse (Project Engineer, CNRS, retired in 2017), Yann Fanteï Caujolle and Sylvain Rousseau (Project Engineer and Research Officer, CNRS, instrument control), and Aurélie Marcotto (Project Engineer, OCA, integration). The team of researchers based in Nice, along with Eric Pantin (CEA-Saclay Researcher) and Jean-Charles Augereau (Astronomer at the Institute for Planetary Sciences and Astrophysics, Grenoble), is part of an international scientific group whose role is to prepare observation programs. To this must be added the support of the general services of the OCA and the J.-L. Lagrange laboratory, particularly through its Director, Philippe Stee, and the people involved in the following activities: IT services, mechanical workshop, clean rooms and administration. We thank the City of Nice and the Consulate General of Chile in Paris for their support regarding the formalities of our most recent mission. Our thoughts are with our colleagues Michel Dugué (Research Officer) and Olivier Chesneau (Astronomer) who left us before the end of the adventure, but whose memory continues with us.