Not all of the universe is quiet.
Some are called active galaxies, where the black hole in their cores is feeding on material. The material forms a flattened disk around the black hole which gets so bright it can surpass all the stars in the galaxy.
Yes, active indeed.
Astronomers have found many different kinds of active galaxies, some of which are very bright in radio and IR light but not as bright in visible light like X- and gamma rays. Quasars and blazars are high-energy forms of light that blast out.
Why are they different? The Unified Model of Active Galaxies is a model that proposes a thick disk of dust around the black hole so thick it blocks the high-energy light from the side. The orientation with respect to us is what changes when you look at all these galaxies. If we see the disk from the side, it blocks a lot of the light, but if we see them face-on, all the high-energy light gets through.
The model does a great job explaining the active galaxies, except for M 77.
This gorgeous spiral galaxy is 45 million light years from Earth and is bright enough to be seen with a small telescope. It has a bright nucleus and has been identified as an active galaxy over the years. According to the Unified Model, we don't see high-energy light from it, so we must be seeing the dust disk more edge-on.
The light from the black hole can be seen from a high angle because the dust ring around the core is too thin. We would see the light if it was blocked. What is going on?
The European Southern Observatory has a Very Large Telescope that has a super-high-resolution IR camera called the Multi Aper Ture mid-Infrared SpectroScopic Experiment.
The observations were made at long wavelength of light, from 3 to 13 microns, with a wavelength from 5 to more than 15 times the reddest light the human eye can see. Light at that wavelength looks at dust of lower temperature than previously observed, and the range allows astronomy to understand the structure in the dust, which will be warmer closer to the black hole.
They were able to get a better idea of the location of the black hole by taking observations from the ALMA. It is lower down in the previously seen ring of material, and is being blocked by a denser disk of material that lasts for several dozen light years.
That's right! The denser material blocks the light that should be coming out of the black hole.
If the Unified Model does not work for one of the closest active galaxies in the Universe, how can we trust it at all, but these new observations support it being the accurate representation.
That is a relief. The Unified Model has done a great job of explaining the many phenomena we see in active galaxies, from the kind of light emitted to the structures that emit them, to a thick torus of dust, focused beams of matter, and energy blasted out called jets. This is a hard-won knowledge that has taken decades to work out, and thousands upon thousands of observations of the universe using telescopes on Earth and in space.
It is nice to see that it works.
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