Astronomers have for the first time a detailed image of an active galactic nucleus, the structure of dust and gas that surrounds a supermassive black hole that is one of the brightest objects in the Universe.
The brightness of this core overshadows that of the galaxy NGC1068 –also called M77– at the center of which it hides. Two centuries after its discovery, astronomers led by Violeta Gamez-Rosa of the Dutch University of Leiden have unraveled its center in great detail in a study published Wednesday in the journal Nature.
Located 47 million light-years away in the constellation of the Whale, M77 is a typical galaxy that harbors an active nucleus: a supermassive black hole, several million solar masses, surrounded by a thick disk of dust and gas, and whose absorption of matter produces gigantic energy.
This core exists for a whole host of extraordinarily luminous objects: quasars, blazars, Seyfert-type galaxies. Its luminosity reaches several thousand times that of an entire galaxy, in 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 an image of something similar, that we actually see the heart of such a galaxy”, explains to AFP the astronomer of the Observatory of the Côte d’Azur, Bruno Lopez, scientific director of Matisse, the instrument for analyzing the light spectrum that made this image possible.
Installed on the European Southern Observatory’s (ESO) Very Large Telescope Interferometer (VLTI), located on a mountain in Chile, MATISSE observes the Universe in mid-infrared.
‘Plasma Jet’
With this range of waves and the precision of the instrument, astronomers can now see “how 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 the winds, to form stars”, continues Bruno Lopez.
Thanks to this image and the accompanying data, the international team of astronomers “has taken a big step in understanding the workings of active galactic nuclei”, says Violeta Gamez-Rosa, quoted in an ESO press release.
The discovery will also help “better understand the history of the Milky Way, whose supermassive black hole sheltered at its center may have been active in the past,” she said.
M77’s black hole, invisible by definition, is surrounded by two disks of gas and dust, which its gravitational pull clumps together as it absorbs it, into a disk of light.
From the center of the nucleus, a jet of plasma – ionized particles – sprouts at each pole, giving the set the appearance of a spinning top. And also clouds of dust and gas “that look like sources of matter, rejected in the lobes of the galaxy”, explains Lopez.
With Matisse, astronomers will now increase their observations of other active galactic nuclei and study dust clouds.
They have already detected large proportions of silicates in M77, similar to those that mainly make up the earth’s crust, and traces of hydrocarbons. This carbon is of great interest even more because it is the fourth largest constituent of the Universe.
