Black holes suck up matter in their surroundings. How this actually happens in the immediate vicinity of these objects, for example what exactly happens when gas crosses the so-called event horizon, i.e. the final boundary beyond which there is no longer any return from the hole, these processes are still the subject of research . Now, for the first time, scientists have been able to understand how molecular gas feeds a supermassive black hole (SMBH) in its close surroundings.
Alma: The telescope for special observations
The hole observed is located at the center of the Circinus Galaxy. This lies in the direction of the southern constellation Circinus (compass). It is one of the closest galaxies to the Milky Way and is only 13 million light-years away from us. Nevertheless, it is one of the less explored galaxies in our immediate vicinity.
To observe the active core of this galaxy, the team was able to use the Alma radio telescope (Atacama Large Millimeter/submillimeter Array) in the Chilean Atacama Desert. The radio telescope can detect wavelengths in the submillimeter range, which enables comparatively high resolutions.
Only three percent of the surrounding gas falls into the black hole
Thanks to Alma, the research team was able to achieve a spatial resolution of 0.5 to 2.6 parsecs, thus obtaining precise data from the closer surroundings of the supermassive black hole. It showed that less than three percent of the dense molecular gas in the central parsec of the active galactic nucleus (AGN) also fell into the hole.
The remainder is expelled by outflows of multiphase gas. This gas, in turn, contributes to the formation of new stars in the galaxy. The research group suspects that a gravitationally unstable, dense disk of gas drives accretion (an astronomical object collects matter like dust particles through its gravitational forces) and that this disk is located within about a parasec around the hole.
What is a parsec?
Parsec is the short form of parallax second and a common astronomical unit for distances in space. For example, this indicates the distances between galaxies.
1 parsec is equal to 3.26 light years – the distance that light can travel in 3.26 years. That’s about 31 trillion kilometers. The unit does not just describe the simple distance. It describes the distance from the Earth to the Sun at an angle of one arcsecond.
How do you measure an arc second?
An arc second is a unit of angular measurement. It corresponds to 1°/3,600 degrees. 60 arcseconds (60”) are combined into one arcminute and 60 arcminutes (60′) are equal to one degree.
One arcsecond is approximately the angle of an object five millimeters wide located at a distance of one kilometer. When measuring, the angle of view and the location from which you look at the sky are crucial.