Observed a supermassive black hole hidden in a ring of cosmic dust
An instrument from the European Astral Observatory has detected a cloud of cosmic dust in the center of the Messier 77 galaxy that hides a supermassive black hole. The finding confirms predictions made some 30 years ago and is giving astronomers new insight into "active galactic nuclei," which are among the brightest and most enigmatic objects in the universe.
Active galactic nuclei (AGN) are high-energy sources powered by supermassive black holes found at the center of some galaxies. These black holes feed on large volumes of cosmic gas and dust. Before being devoured, this material spirals towards the black hole, releasing enormous amounts of energy in the process, often dwarfing all the stars in the galaxy.
The phenomenon has been observed by the Very Large Telescope Interferometer (VLTI, in its English acronym, of the European Southern Observatory, which has published the finding in the journal Nature this Wednesday and explained details in a statement.
Shiny objects in the 50's
Astronomers have been curious about AGNs since they first saw these bright objects in the 1950s. Now, thanks to ESO's VLTI, a team of researchers, led by Violeta Gámez Rosas of Leiden University in the Netherlands ), has taken a key step in understanding how they work and what they look like up close.
Making extraordinarily detailed observations of the center of the galaxy Messier 77, also known as NGC 1068, Gámez Rosas and his team detected a thick ring of cosmic gas and dust that hides a supermassive black hole. This discovery provides vital evidence to support a 30-year-old theory known as the 'Unified Model of AGN'.
Astronomers know that there are different types of AGN. For example, some emit bursts of radio waves and some do not; some AGNs glow in visible light, while others, like Messier 77, are dimmer. The unified model asserts that, despite their differences, all AGNs have the same basic structure: a supermassive black hole surrounded by a thick ring of dust.
The presence of this dust –in a thick inner ring and a more extensive disk– and the black hole located in its center support the prediction made by the Unified Model.
According to this model, any difference in appearance between the AGNs is a result of the orientation in 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 point of view, obscuring it completely in some cases.
An observation that dispels doubts
Astronomers had already found some evidence to support the Unified Model, including the detection of hot dust at the center of Messier 77. However, questions remained as to whether this dust could completely hide a black hole, and thus explain why. this AGN glows less in visible light than others.
"The actual nature of the dust clouds and their role in both feeding the black hole and determining what it looks like when viewed from Earth have been central questions in AGN studies for the past three decades," he explains. Gamez Rosas. "Although no single result will answer all the questions we have, we have taken an important step in understanding how AGNs work."
The observations were made possible by the Multiple Aperture Mid-Infrared Spectroscopic Experiment (MATISSE) mounted on ESO's VLTI, located in the Atacama Desert, Chile. MATISSE combined the infrared light collected by the four 8.2-metre telescopes of ESO's Very Large Telescope (VLT) using a technique called interferometry. The team used MATISSE to scan the center of Messier 77, located 47 million light-years away in the constellation Cetus.
changes in temperature
"MATISSE can see a wide range of infrared wavelengths, allowing us to see through dust and accurately measure temperatures. As the VLTI is, in fact, a very large interferometer, we have the resolution to see what it occurs 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, professor at Leiden University.
The team built a detailed image of the dust and pinpointed where the black hole should be. It did this by combining, with the absorption maps, the changes caused by the intense black hole radiation in the temperature of the dust (from room temperature to about 1,200 °C).
The presence of this dust –in a thick inner ring and a more extensive disk– and the black hole located in its center support the prediction made by the Unified Model.
"Our results should lead to a better understanding of the internal workings of AGN", concludes Gámez Rosas. "They could also help us better understand the history of the Milky Way, which harbors a supermassive black hole at its center that may have been active in the past."
