Galaxy Messier 77 and close-up view of its active centre
A close-up view of Messier 77’s active galactic nucleus
Dazzling galaxy Messier 77
Artist’s impression of the active galactic nucleus of Messier 77
The active galaxy Messier 77 in the constellation of Cetus
Wide-field image of the sky around Messier 77
Video
Artist’s animation of the active galactic nucleus of Messier 77
The Unified Model of active galactic nuclei
The European Southern Observatory’s Very
Large Telescope Interferometer (ESO’s VLTI) has observed a cloud of
cosmic dust at the centre of the galaxy Messier 77 that is hiding a
supermassive black hole. The findings have confirmed predictions made
around 30 years ago and are giving astronomers new insight into “active
galactic nuclei”, some of the brightest and most enigmatic objects in
the universe.
Active galactic nuclei
(AGNs) are extremely energetic sources powered by supermassive black
holes and found at the centre of some galaxies. These black holes feed
on large volumes of cosmic dust and gas. Before it is eaten up, this
material spirals towards the black hole and huge amounts of energy are
released in the process, often outshining all the stars in the galaxy.
Astronomers have been curious about AGNs ever since they first
spotted these bright objects in the 1950s. Now, thanks to ESO’s VLTI, a
team of researchers, led by Violeta Gámez Rosas from Leiden University
in the Netherlands, have taken a key step towards understanding how they
work and what they look like up close. The results are published today
in Nature.
By making extraordinarily detailed observations of the centre of the galaxy Messier 77,
also known as NGC 1068, Gámez Rosas and her team detected a thick ring
of cosmic dust and gas hiding a supermassive black hole. This discovery
provides vital evidence to support a 30-year-old theory known as the
Unified Model of AGNs.
Astronomers know there are different types of AGN. For example, some
release bursts of radio waves while others don’t; certain AGNs shine
brightly in visible light, while others, like Messier 77, are more
subdued. The Unified Model states that despite their differences, all
AGNs have the same basic structure: a supermassive black hole surrounded
by a thick ring of dust.
According to this model, any difference in appearance between AGNs
results from the orientation at which we view the black hole and its
thick ring from Earth. The type of AGN we see depends on how much the
ring obscures the black hole from our view point, completely hiding it
in some cases.
Astronomers had found some evidence to support the Unified Model
before, including spotting warm dust at the centre of Messier 77.
However, doubts remained about whether this dust could completely hide a
black hole and hence explain why this AGN shines less brightly in
visible light than others.
“The real nature of the dust clouds and their role in both
feeding the black hole and determining how it looks when viewed from
Earth have been central questions in AGN studies over the last three
decades,” explains Gámez Rosas. “Whilst no single result will settle all the questions we have, we have taken a major step in understanding how AGNs work.”
The observations were made possible thanks to the Multi AperTure mid-Infrared SpectroScopic Experiment (MATISSE) mounted on ESO’s VLTI,
located in Chile’s Atacama Desert. MATISSE combined infrared light
collected by all four 8.2-metre telescopes of ESO’s Very Large Telescope
(VLT) using a technique called interferometry. The team used MATISSE to
scan the centre of Messier 77, located 47 million light-years away in
the constellation Cetus.
“MATISSE can see a broad range of infrared wavelengths, which
lets us see through the dust and accurately measure temperatures.
Because the VLTI is in fact a very large interferometer, we have the
resolution to see what’s going on even in galaxies as far away as
Messier 77. The images we obtained detail the changes in temperature and
absorption of the dust clouds around the black hole,” says co-author Walter Jaffe, a professor at Leiden University.
Combining the changes in dust temperature (from around room
temperature to about 1200 °C) caused by the intense radiation from the
black hole with the absorption maps, the team built up a detailed
picture of the dust and pinpointed where the black hole must lie. The
dust — in a thick inner ring and a more extended disc — with the black
hole positioned at its centre supports the Unified Model. The team also
used data from the Atacama Large Millimeter/submillimeter Array,
co-owned by ESO, and the National Radio Astronomy Observatory’s Very
Long Baseline Array to construct their picture.
“Our results should lead to a better understanding of the inner workings of AGNs,” concludes Gámez Rosas. “They
could also help us better understand the history of the Milky Way,
which harbours a supermassive black hole at its centre that may have
been active in the past.”
The researchers are now looking to use ESO’s VLTI to find more
supporting evidence of the Unified Model of AGNs by considering a larger
sample of galaxies.
Team member Bruno Lopez, the MATISSE Principal Investigator at the Observatoire de la Côte d’Azur in Nice, France, says: “Messier
77 is an important prototype AGN and a wonderful motivation to expand
our observing programme and to optimise MATISSE to tackle a wider sample
of AGNs."
ESO’s Extremely Large Telescope (ELT),
set to begin observing later this decade, will also aid the search,
providing results that will complement the team’s findings and allow
them to explore the interaction between AGNs and galaxies.
More Information This research was presented in the paper “Thermal imaging of dust hiding the black hole in the Active Galaxy NGC 1068” (doi: 10.1038/s41586-021-04311-7) to appear in Nature.
The team is composed of Violeta Gámez Rosas (Leiden Observatory,
Leiden University, Netherlands [Leiden]), Jacob W. Isbell (Max Planck
Institute for Astronomy, Heidelberg, Germany [MPIA]), Walter Jaffe
(Leiden), Romain G. Petrov (Université Côte d’Azur, Observatoire de la
Côte d’Azur, CNRS, Laboratoire Lagrange, France [OCA]), James H. Leftley
(OCA), Karl-Heinz Hofmann (Max Planck Institute for Radio Astronomy,
Bonn, Germany [MPIfR]), Florentin Millour (OCA), Leonard Burtscher
(Leiden), Klaus Meisenheimer (MPIA), Anthony Meilland (OCA), Laurens B.
F. M. Waters (Department of Astrophysics/IMAPP, Radboud University, the
Netherlands; SRON, Netherlands Institute for Space Research, the
Netherlands), Bruno Lopez (OCA), Stéphane Lagarde (OCA), Gerd Weigelt
(MPIfR), Philippe Berio (OCA), Fatme Allouche (OCA), Sylvie Robbe-Dubois
(OCA), Pierre Cruzalèbes (OCA), Felix Bettonvil (ASTRON, Dwingeloo, the
Netherlands [ASTRON]), Thomas Henning (MPIA), Jean-Charles Augereau
(Univ. Grenoble Alpes, CNRS, Institute for Planetary sciences and
Astrophysics, France [IPAG]), Pierre Antonelli (OCA), Udo Beckmann
(MPIfR), Roy van Boekel (MPIA), Philippe Bendjoya (OCA), William C.
Danchi (NASA Goddard Space Flight Center, Greenbelt, USA), Carsten
Dominik (Anton Pannekoek Institute for Astronomy, University of
Amsterdam, The Netherlands [API]), Julien Drevon (OCA), Jack F.
Gallimore (Department of Physics and Astronomy, Bucknell University,
Lewisburg, Pennsylvania, USA), Uwe Graser (MPIA), Matthias Heininger
(MPIfR), Vincent Hocdé (OCA), Michiel Hogerheijde (Leiden; API), Josef
Hron (Department of Astrophysics, University of Vienna, Austria),
Caterina M.V. Impellizzeri (Leiden), Lucia Klarmann (MPIA), Elena
Kokoulina (OCA), Lucas Labadie (1st Institute of Physics, University of
Cologne, Germany), Michael Lehmitz (MPIA), Alexis Matter (OCA), Claudia
Paladini (European Southern Observatory, Santiago, Chile [ESO-Chile]),
Eric Pantin (Centre d'Etudes de Saclay, Gif-sur-Yvette, France),
Jörg-Uwe Pott (MPIA), Dieter Schertl (MPIfR), Anthony Soulain (Sydney
Institute for Astronomy, University of Sydney, Australia [SIfA]),
Philippe Stee (OCA), Konrad Tristram (ESO-Chile), Jozsef Varga (Leiden),
Julien Woillez (European Southern Observatory, Garching bei München,
Germany [ESO]), Sebastian Wolf (Institute for Theoretical Physics and
Astrophysics, University of Kiel, Germany), Gideon Yoffe (MPIA), and
Gerard Zins (ESO-Chile).
MATISSE was designed, funded and built in close collaboration with
ESO, by a consortium composed of institutes in France (J.-L. Lagrange
Laboratory — INSU-CNRS — Côte d’Azur Observatory — University of Nice
Sophia-Antipolis), Germany (MPIA, MPIfR and University of Kiel), the
Netherlands (NOVA and University of Leiden), and Austria (University of
Vienna). The Konkoly Observatory and Cologne University have also
provided some support in the manufacture of the instrument.
The European Southern Observatory (ESO) enables scientists worldwide
to discover the secrets of the Universe for the benefit of all. We
design, build and operate world-class observatories on the ground —
which astronomers use to tackle exciting questions and spread the
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planetarium, the ESO Supernova, are located close to Munich in Germany,
while the Chilean Atacama Desert, a marvellous place with unique
conditions to observe the sky, hosts our telescopes. ESO operates three
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operates the Very Large Telescope and its Very Large Telescope
Interferometer, as well as two survey telescopes, VISTA working in the
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will host and operate the Cherenkov Telescope Array South, the world’s
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Links
Contacts:
Violeta Gámez Rosas
Leiden University
Leiden, the Netherlands
Tel: +31 71 527 5737
Email: gamez@strw.leidenuniv.nl
Walter Jaffe
Leiden University
Leiden, the Netherlands
Tel: +31 71 527 5737
Email: jaffe@strw.leidenuniv.nl
Bruno Lopez
MATISSE Principal Investigator
Observatoire de la Côte d’ Azur, Nice, France
Tel: +33 4 92 00 30 11
Email: Bruno.Lopez@oca.eu
Romain Petrov
MATISSE Project Scientist
Observatoire de la Côte d’ Azur, Nice, France
Tel: +33 4 92 00 30 11
Email: Romain.Petrov@oca.eu
Bárbara Ferreira
ESO Media Manager
Garching bei München, Germany
Tel: +49 89 3200 6670
Cell: +49 151 241 664 00
Email: press@eso.org
Source: ESO/News
