Fifty-five million light-years from Earth is a monster.
It is a supermassive black hole, one with a mass equivalent of 6.5 billion The sun. It may be hiding among the stars of the huge elliptical galaxy M87, but it’s doing badly. It’s right in the middle of the galaxy, the first place we look. Also, as it feeds, it radiates radiation from the material that falls into it, making it bright and obvious.
And it also roars. Two long jets of material scream away at him with a high percentage of the speed of light; fed, focused, and triggered by magnetic fields wrapped in material as it revolves around the Point of no return.
We are lucky that he is not very bad about attention. Because we follow it closely, using a literal fleet of observers both on and above Earth.
You’ve probably seen the incredible image of the material around the M87’s supermassive black central hole. The first was launched in 2019 and was a revolution, showing the shadow of the back hole, the region around it, where even photons cannot orbit stably. Not long after astronomers saw changes in the material over time. And then, just a few weeks ago, a second version was published that shows the effects of the ridiculously strong magnetic field wrapped around that matter.
All this data was taken by the 2017 radio telescopes scattered on Earth, combining their power to obtain the intense view of a virtual telescope the size of a planet, called the Event Horizon telescope.
Almost at the same time, 19 observers monitoring the light in the electromagnetic spectrum, from radio waves to gamma rays, also observed the black hole. This type of campaign, called synoptic observations, helps astronomers understand what is happening only at different energies, but also at different spatial scales around the black hole.
For example, the mass of the black hole is known only with an uncertainty of about 10%. The mass is determined by how it swallows all the material seen in those images. But physical models must be used to determine mass, and they make assumptions about some features that are not well known. Observations at different wavelengths can help fix them better.
Also, that jet of material flowing away from the black hole is a mystery. The details of how exactly the ferocious magnetic field unfolds in the material orbiting the black hole are not well understood, nor how it actually accelerates the jets away from the intense gravity of the black hole. And what happens inside the jet as the material floods at such high speeds? We see crowds in the jet and, in some places, faster clouds of gas hit the material that moves more slowly in front of them, creating huge shock waves. What effect does this have?
And the space ladder, pretty. The jet starts very close to the black hole, just a few tens of billions of kilometers from it, but stretches on 200,000 light-years – It’s longer than the Milky Way! You have to use different telescopes that look at all these scales – which have different magnifications, if you will – to even have a prayer to understand what is going on in this maelstrom.
The almost simultaneous observations of the black hole and the jet were made using the Event Horizon Telescope, but also Hubble (visible light), Chandra (X-rays), Fermi (gamma rays), Swift (X-rays and gamma rays), NuSTAR (X-rays) ) and more. For a brief moment, some of the astronomers’ strongest eyes were blocked on the M87.
All this data was communicated to the astronomy public, so that scientists eager to attack it and use it to perfect their theoretical models. But the team (over 750 scientists from nearly 200 institutions and 32 countries) managed to draw some preliminary conclusions based on what they saw.
First, activity in the supermassive black hole was at a historically low level during observations. The material falls into the black hole at different speeds. Sometimes it is a constant current, and its brightness is constant, sometimes a large cloud of gas or a star falls and shines considerably, and sometimes less matter falls and the black hole is temporarily starving, so it fades. The low activity was, in some respects, useful because it allowed astronomers to obtain observations so close (it will be useful when we obtain observations similar to this for our own local supermassive black hole, Sgr A *).
We are pretty sure that the environment around black holes can also produce incredibly large cosmic rays, which are subatomic particles such as protons and nuclei of helium atoms that move at almost the speed of light. Cosmic rays can reach our atmosphere and subtly affect the chemistry of the air and rocks on the surface. They are also a key to understanding other subatomic particles and even the fact that they exist can tell us how black holes generate them. Some are probably made in those shock waves of the jet, but others may come from near the black hole.
Cosmic rays can cause gamma rays to collapse inside the material, and new observations have analyzed that extremely high end of energy in the spectrum. They found very little gamma-ray light coming from near the black hole, which is a bit surprising. Does this mean that the jet dominates the cosmic rays? Or is this low number of gamma rays due to the low activity observed in the black hole?
We hope that the new data will be extremely useful for astronomers trying to figure out what all the moving parts here are doing. It’s incredibly complex and we’re just beginning to understand it.
One thing I know for sure is that this is not enough to satiate astronomers. In a way, it is very similar to the objects it studies: surrounded by massive amounts of data, voracious consumers of them, always wanting more, and sometimes throwing information and conclusions with high energy and at high speeds.
So stay tuned. A new stream of information from these observations will no doubt soon be in our direction.