The brilliance of this nucleus greatly eclipses that of the galaxy NGC1068 -- also called M77 -- at the center of which it lurks.

Two centuries after its discovery, astronomers led by Violeta Gamez-Rosa, of the Dutch University of Leiden, unveil the heart of it with a wealth of detail, in a study published Wednesday by Nature.

Located 47 million light years away, in the constellation of the Whale, M77 is typical of galaxies harboring an active galactic nucleus: a supermassive black hole, several million solar masses, surrounded by a thick disc of dust and gas, and whose absorption of matter produces phenomenal energy.

This nucleus exists for a whole series of extraordinarily luminous objects: quasars, blazars, Seyfert-type galaxies.

Their luminosity reaches several thousand times that of an entire galaxy, from an area as "small" as the equivalent of our solar system, notes a Nature article accompanying the study.

"This is the first time that we have obtained the image of such a thing, that we really see the heart of such a galaxy", explains to AFP the astronomer at the Côte d'Observatory. Azur, Bruno Lopez, scientific manager of MATISSE, the instrument for analyzing the light spectrum which made this image possible.

Images showing the galactic nucleus on the right as seen with the MATISSE instrument, and its position on the left in the galaxy M77, in a composite provided by the European Southern Observatory on February 16, 2022 - European Southern Observatory/AFP

Installed on the Very Large Telescope Interferometer (VLTI) of the European Southern Observatory (ESO), itself perched on a mountain in Chile, MATISSE observes the Universe in the mid-infrared.

"Plasma Jet"

With this range of waves and the precision of the instrument, astronomers can now see "how the matter organizes itself around the active nucleus, how it feeds the black hole, but also how it organizes itself according to the energy released, with winds, to form stars", continues Bruno Lopez.

Thanks to this image and the accompanying data, the international team of astronomers has "taken a major step in understanding the functioning of active galactic nuclei", says Violeta Gamez-Rosa, quoted in an ESO press release. .

Image of the galaxy M77 (NGC1068) taken with the spectrograph of the Very Large Telescope of the European Southern Observatory and provided by the latter on February 16, 2022 - European Southern Observatory/AFP

The discovery will also help "to better understand the history of the Milky Way, whose supermassive black hole sheltered at its center may have been active in the past", according to her.

The black hole of M77, invisible by definition, is surrounded by two discs of gas and dust, which its gravitational force agglomerates while absorbing it, in a disc of light.

From the center of the core springs at each pole a jet of plasma -- ionized particles --, giving the whole the appearance of a spinning top.

And also clouds of dust and gas "which look like fountains of matter, rejected in the lobes of the galaxy", explains Mr. Lopez.

With MATISSE, astronomers will now increase their observations of other active galactic nuclei, and study dust clouds.

They have already detected in those of M77 large proportions of silicates, similar to those which mainly make up the earth's crust, and traces of hydrocarbons.

This carbon interests them all the more because it is the fourth major constituent of the Universe.

© 2022 AFP