Fifty-five million light-years from Earth lies a monster.
It is a supermassive black hole, one with the mass equivalent of 6.5 billion Sun tanning. It may be hiding among the stars of the massive elliptical galaxy M87, but it is doing poorly. It’s right in the center of the galaxy, the first place we would look. As it feeds, it also blows radiation from the material that falls into it, making it crisp and clear.
And it roars too. Two long beams of material scream away from it at a high percentage of the speed of light; fed, focused and fired by magnetic fields wrapped in the material as it swirls around The Point of No Return.
We are lucky that it is not very cautious about attention. Because we’re watching it closely, using a literal fleet of observatories both on and above Earth.
You’ve probably seen the incredible image of material surrounding M87’s central supermassive black hole. The first was released in 2019 and was a revolution that showed the shadow of the rear hole, the area around it where even photons cannot orbit stably. Not long after, astronomers saw changes in that material over time. And then, just weeks ago, a second version was published showing the effects of the ridiculously powerful magnetic field wrapped in that matter.
All that data was collected by radio telescopes scattered around Earth in 2017, combining their power to achieve the sharp eyesight of a planet-sized virtual telescope called the Event Horizon telescope.
Almost simultaneously, 19 observatories that light across the entire electromagnetic spectrum, from radio waves to gamma rays, also observed the black hole. This type of campaign, called synoptic observations, helps astronomers understand what only happens at different energies, but also at different spatial scales around the black hole.
For example, the mass of the black hole is only known with an uncertainty of about 10%. The mass is determined by how it gobbles up all of the material in those images. But physical models must be used to determine mass, and they make assumptions about some characteristics that are not well known. Observations at different wavelengths can help to determine them better.
The jet of material that flows out of the black hole is also a mystery. The details of exactly how the bright magnetic field enters the material surrounding the black hole are not well understood, nor how it actually accelerates the jets away from the black hole’s intense gravity. And what happens in the jet if the material flows away at such high speeds? We see lumps in the jet and in places faster gas clouds crash into slower moving material in front of them, creating massive shock waves. What effect does that have?
And the spatial scale, howls. The jet starts very close to the black hole, just a few tens of billions of miles away, but stretches ahead 200,000 light years – it is longer than our own Milky Way! You have to use different telescopes that look at all these scales – which have different magnifications, if you want – to even have a prayer to understand what’s going on in this maelstrom.
The near-simultaneous observations of the black hole and the jet were made with the Event Horizon Telescope, as well as with Hubble (visible light), Chandra (X-rays), Fermi (gamma rays), Swift (X-rays and gamma rays), NuSTAR (X-rays) , and more. For a moment, some of the most powerful eyes that astronomers have were all focused on M87.
All of that data has been released to the astronomical public so that avid scientists can attack and use it to hone their theoretical models. But the team (more than 750 scientists from nearly 200 institutions and 32 countries) was able to draw some preliminary conclusions based on what they saw.
For one thing, the supermassive black hole’s activity was at an all-time low during the observations. Material falls into the black hole at different speeds. Sometimes it is a steady stream and the brightness is also stable, sometimes a large cloud of gas or star falls into it and becomes significantly brighter, and sometimes less matter falls in and the black hole is temporarily starved, so that it dims. The low activity was useful in some ways, as it allowed astronomers to get observations so close (it will also be helpful if we get similar observations for our own local supermassive black hole, Sgr A *, too).
We are pretty sure that the environment around black holes can also produce incredibly high-energy cosmic rays, which are subatomic particles such as protons and helium nuclei that move almost at the speed of light. Cosmic rays can strike our atmosphere and subtly affect the chemistry of the air and rocks on the surface. They are also key to understanding other subatomic particles, and the fact that they exist can tell us about how black holes generate them. Some were likely created in those jet shock waves, but some can get up close to the black hole.
Cosmic rays can strike gamma rays around the innermost material, and the new observations looked at that extremely high-energy end of the spectrum. They found very little gamma-ray light coming from close to the black hole, which is a bit surprising. Does this mean that the jet dominates when creating cosmic rays? Or is this low number of gamma rays due to the low activity seen from the black hole?
Hopefully the new data will be extremely helpful to astronomers trying to figure out what all the moving parts are doing here. It’s incredibly complex and we’re only just beginning to understand it.
One thing I’m sure is that this isn’t enough to saturate astronomers. In a way, they are very similar to the objects they study: surrounded by vast amounts of data, gluttonous consumers of it, always wanting more, and sometimes blowing out information and conclusions with high energy and speeds.
So stay tuned. A new beam of information from these observations will no doubt be heading our way soon.