In the constellation of the Whale, 47 million light–years from Earth, lies the spiral galaxy Messier 77. And in its center there is an extremely massive black hole - as it can be assumed from almost all galaxies. However, Messier 77, also known as NGC 1068, has a special feature: it has a so-called active galactic nucleus, short AGN from English "active galactic nucleus".
It is a galaxy center that releases an exceptionally large amount of radiation and thus appears particularly bright in the starry sky.
The radiation arises because the black hole swings dust and gas from the surrounding accretion disc.
But since astronomers saw the first AGNs, they have documented differences: some brighter than the others.
The question therefore was whether the active galaxy nuclei are structured differently, different physical conditions in them.
Back in 2018, images taken by the ALMA telescope network in Chile's Atacama Desert revealed a ring of dust and gas, a torus, around the black hole of Messier 77. The research group led by Masatoshi Imanishi from the National Astronomical Observatory in Japan suspected that the differences between the AGNs were due to such dust rings – they would dampen the brightness of the radiation.
The standard model of the AGN also corresponds to the same thesis. It says that the orientation of the dust ring affects how a galaxy is seen from Earth – brighter or less bright. In essence, however, they would all be the same: there is an extremely massive black hole surrounded by a dense ring of dust.
More precise recordings thanks to four telescopes
The model was formulated in the early 1990s and later doubted. But a recent study now confirms the assumption again. As a research group led by Violeta Gámez Rosas from Leiden University describes in Nature, they secured precise images of the galaxy center of Messier 77. For this purpose, they used the MATISSE instrument of the Very Large Telescope Interferometer of the European Southern Observatory in the Atacama Desert in Chile. MATISSE bundles the infrared light measurements from four telescopes. This helped the team to record the local temperature differences and thus pinpoint the position of the black hole and dust ring more accurately. The result corresponded to the prediction of the Standard Model: The dust torus surrounds a black hole, which in this case is enveloped by the ring. Therefore, the view of the center is impaired.
In an accompanying comment in "Nature", the cosmologist and expert for AGNS, Robert Antonucci, agrees with the results of the colleague euphoric. In summary, he writes: "This is a great job!"
