10 scientific facts that we learned from the first pictures of a black hole

The idea of black holes dates back to 1783, when the Cambridge scholar John Michell realized that a sufficiently massive object in a sufficiently small space can attract even light, preventing him from escaping. Over a century later, Karl Schwarzschild found an exact solution for the General theory of relativity, which predicted the same result: a black hole. As Michelle and Schwarzschild predicted a clear link between the event horizon, or the radius of the area from which light can not escape, and the mass of the black hole.

For 103 years after Schwarzschild’s predictions could not be verified. And only 10 April 2019, scientists revealed the first ever photo of the event horizon. Einstein’s theory worked again, as always.

Although we already knew about black holes quite a lot, even before the first image of the event horizon, he was much changed and clarified. We had a lot of questions that now have answers.

By the way, here’s 10 facts about black holes that everyone should know.

10 April 2019 Event Horizon Telescope collaboration presented the first successful the event horizon of a black hole. The black hole is located in the galaxy Messier 87: the largest and most massive galaxy in our local supercluster of galaxies. The angular diameter of the event horizon was 42 micro-arc-seconds. This means that in order to cover the whole sky, have 23 quadrillion black holes of the same size.

At a distance of 55 million light-years, the estimated mass of the black hole is 6.5 billion times the sun. Physically this corresponds to a size exceeding the size of the orbit of Pluto around the Sun. If the black hole were not, light would take about a day to pass through the diameter of the event horizon. And just because:

  • at the Telescope the event horizon enough resolution to see the black hole
  • the black hole strongly emits radio waves
  • very little radio wave radiation in the background to interfere with the signal

we were able to build this first picture. And now we have learned profound lessons ten.

We know what it looks like a black hole. What’s next?

It’s true black hole, as predicted by General relativity. If you have ever seen an article called something like “theorist boldly claim that black holes do not exist” or “this new theory of gravity may overturn Einstein”, you realize that physicists have no problems with coming up with alternative theories. Despite the fact that General relativity has passed all the tests, which we were subjected, the lack of extensions, replacements or possible alternatives to the physicists there.

And the observation of a black hole eliminates a huge number of them. Now we know that it is a black hole, not a wormhole. We know that the event horizon exists and that this is not a naked singularity. We know that the event horizon is not a solid surface, because the incident agent has to give an infrared signature. All these observations support the General theory of relativity.

However, this observation says nothing about dark matter, the most modified theories of gravity, quantum gravity, or that disappears behind the event horizon. These ideas are beyond the scope of EHT observations.

The gravitational dynamics of stars gives good estimates for the masses of black holes; observations of gas — no. To the first image of the black hole we had several different ways to measure the masses of black holes.

We could either use a measuring star — like orbits of individual stars near the black hole in our own galaxy, or absorption lines of stars in M87 — which gave us the gravitational mass, or of emissions from gas that is moving around the Central black hole.

Like our galaxy and M87, the two scores were very different: the gravity assessment was 50-90% more than gas. For M87 gas measurement showed that the black hole mass are 3.5 billion suns, and gravity measurements were closer to the 6.2 — 6.6 billion But the results of EHT revealed that the black hole is of 6.5 billion solar masses, and thus the gravitational dynamics — a great indicator of black hole mass, but the findings for gas are displaced toward lower values. This is a great opportunity to revise our assumptions about the astrophysical orbital gas.

It should be a rotating black hole, and its axis of rotation points in the direction from the Earth. Through observation of the event horizon, the radio emission around it, the large-scale jet and extended radio emission measured by other observatories, EHT has determined that it is a black hole of Kerr (rotating) and not the Schwarzschild (non-rotating).

Not a single simple line of black holes that we could examine to determine this nature. Instead, we have to build models most of the black hole and the matter outside of it, and then to develop them, to understand what is happening. When you are looking for possible signals that may occur, you be able to restrict them so that they are consistent with your results. This black hole must rotate, and the rotation axis points from the Earth by about 17 degrees.

We were finally able to determine that around a black hole there is a substance corresponding accretion disks and streams. We already knew that was the M87 jet in the optical observations — and that it was emitted in the radio and x-ray ranges. This kind of radiation can’t get just from stars or of photons: you need the substance and the electrons. Only acceleration of electrons in a magnetic field it is possible to obtain a characteristic radiation, which we saw the synchrotron radiation.

And it has also required an incredible amount of work on modeling. Twisting the parameters of all possible models, you will know that these observations will not only require the accretion flows to explain radioresistance, but not necessarily predict-wave results — such as x-ray radiation. The most important observation made not only the EHT, but other observatories like the x-ray telescope “Chandra”. Accretion flows must be heated, as evidenced by the range of the magnetic radiation of M87, in accordance with the relativistic acceleration of electrons in a magnetic field.

The visible ring demonstrates the strength of gravitation and gravitational lensing around a Central black hole; General relativity and again tested. This ring is in the radio corresponds to the event horizon and does not correspond to a ring of rotating particles. And it’s also not the most stable circular orbit of a black hole. No, this ring arises from the gravitational sphere linterweb photons whose paths are bent by the gravity of a black hole on the way to our eyes.

This light is bent in a large field than would be expected if gravity was not that strong. Writes to Event Horizon Telescope Collaboration:

“We found that more than 50% of the total flow in arcsecond is near the horizon and that this radiation is dramatically suppressed when hit in this area, 10 times, which is a direct proof of the predicted shadow of the black hole”.

The General theory of relativity Einstein was once again correct.

Black holes are dynamic phenomena, their radiation is changing with time. With a mass of 6.5 billion suns, the world will need about a day to overcome the event horizon of a black hole. This roughly sets the time frame in which we can expect to see the changes and fluctuations of the radiation observed EHT.

Even observations that lasted for several days, allowed us to confirm that the structure of the emitted radiation changes with time, as predicted. The data for 2017 contain four nights of observations. Even looking at these four images you can visually see that the first two have similar features and the last two also, but between the first and the last there are significant differences. In other words, the properties of the radiation around the black hole in M87 do change over time.

EHT in the future will reveal the physical origin of the flares of black holes. We saw in the x-ray and in the radio that a black hole at the center of our own milky Way emits a short flash of radiation. Although the first presents the image of a black hole showed a supermassive object in M87, the black hole in our galaxy — Sagittarius A* — there will be this great, the only change will be faster.

In comparison with the mass of M87 6.5 billion solar masses — the mass of Sagittarius A* is 4 million solar masses: 0.06% down from the first. This means that fluctuations will occur not in the course of the day, for even one minute. Features of the black hole will change quickly, and when outbreaks occur, we can discover its nature.

As outbreaks are associated with temperature and luminosity of radiocative that we saw? Does magnetic reconnection as the coronal mass ejection of our Sun? Something is broken in the accretion flows? Sagittarius a* flares up daily, so we can tie all the right signals with these events. If our models and observations will be as good as they were for M87, we will be able to determine what drives these events and maybe even find out what falling into a black hole, creating them.

Appears the polarization data that will reveal whether a black hole’s own magnetic field. Although we all were definitely happy to see the first picture of the event horizon of a black hole, it is important to understand that soon there will be a completely unique pattern: polarization of the light emanating from the black hole. Because of the electromagnetic nature of light its interaction with the magnetic field will print a special polarization signature on it, allowing us to reconstruct the magnetic field of a black hole, but also how it changes over time.

We know that the substance outside the event horizon, being essentially moving charged particles (like electrons), generates its own magnetic field. Models indicate that the field lines can either stay in the accretion flow or pass through the event horizon, forming a kind of “anchor” in a black hole. Is there a connection between these magnetic fields, accretion and growth of black holes and jets. Without these fields, matter in the accretion flows would not be able to lose angular momentum and fall into the event horizon.

The polarization data, the strength of polarimetric imaging will tell us about it. The data we already have: we just have to perform a complete analysis.

The improvement of the Event Horizon Telescope will show the presence of other black holes near galactic centers. When a planet revolves around the Sun, it is connected not only with the fact that the Sun has a gravitational effect on the planet. There is always an equal and opposite reaction: the planet affects the sun. Similarly, when the object is circling around the black hole, it also has the gravitational pressure of a black hole. In the presence of a set of mass near the centers of galaxies — and, in theory, many of the invisible yet black holes Central black hole should be literally shaking in your seat, being pulled apart by Brownian motion of surrounding bodies.

The complexity of carrying out this measurement today is that you need a reference point to calibrate your position relative to the location of the black hole. The technique for such measurement implies that you are looking at a calibrator, then to the source, back to the calibrator back to the source, and so on. To move the view very quickly. Unfortunately, the atmosphere is changing very rapidly, and in 1 second a lot can change, so you simply will not have time to compare two objects. In any case, not with modern technology.

But technology in this area are developing extremely fast. The instruments used in EHT, expect updates and may be able to achieve the necessary speed to the mid 2020-ies. This puzzle can be resolved by the end of the next decade, thanks to improved instrumentation.

Finally,the Event Horizon Telescope will eventually see hundreds of black holes. To dismantle a black hole, it is necessary that the resolving power of the array of the telescope was better (i.e. higher resolution) than the size of the object you are looking for. Currently, the EHT can only make out three known black holes in the Universe with a large enough diameter: Sagittarius A*, the center of M87, the Central galaxy NGC 1277.

But we can increase the power of the eye Event Horizon Telescope the size of Earth, if launch telescopes into orbit. In theory, this is technically achievable. Increasing the number of telescopes increases the number and frequency of observations, along with the resolution.

Making the necessary improvements, instead of 2-3 galaxies we will be able to find hundreds of black holes or even more. The future of photo albums with black holes seems bright.

The project of Telescope event horizon was expensive, but it paid off. Today we live in an era of astronomy black holes and finally able to observe them firsthand. This is only the beginning. Subscribe to our feed in the Telegramto get all the news from this invisible front.

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