This, too, took an amazing amount of simulation work. Only by accelerating electrons in a magnetic field can you get the characteristic radio emission that we've seen: synchrotron radiation. You can't really get that type of radiation from stars or photons alone you need matter, and electrons in particular. We already knew that M87 had a jet from the optical observations, and that it also emitted radio waves and X-rays. We were able to definitively determine that there is matter, consistent with accretion disks and flows, around the black hole. our picture of how black hole engines ought to work for a long time, the Event Horizon Telescope has provided new evidence validating it. The black hole must be rotating, and the rotational axis points away from Earth at about 17 degrees.Ĭoncept art of an accretion ring and jet around a supermassive black hole. When you look at the various signals that could emerge, you gain the ability to constrain what's possibly consistent with your results. Rather, we have to construct dazzling models of the black hole itself and the matter outside of it, and then evolve them to see what occurs. There's no one simple feature we can look at to tease out this nature. With observations of the event horizon, the radio emissions surrounding it, the large-scale jet, and the extended radio emissions that were measured previously by other observatories, the Event Horizon Telescope Collaboration has determined that this must be a Kerr (rotating) and not a Schwarzschild (non-rotating) black hole. This has to be a rotating black hole, and its rotation axis happens to point away from Earth. This optical image showcases a jet we now know, from the Event Horizon Telescope, that the rotation axis of the black hole points away from Earth, tilted at about 17 degrees.
relativistic jet, as well as outflows that show up in both the radio and X-ray. Located approximately 55 million light-years from Earth, the galaxy M87 contains an enormous.
It's a great opportunity to reexamine our astrophysics assumptions about the orbiting gas. For M87, the gas measurements indicated a black hole mass of 3.5 billion Suns, while the gravitational measurements were closer to 6.2-6.6 billion. From the Event Horizon Telescope's results, the black hole weighs in at 6.5 billion solar masses, telling us that gravitational dynamics are good tracers of black hole masses, but inferences from gas are biased towards lower values. We could either use measurements of stars - such as the individual orbits of stars around the black hole in our own galaxy or the absorption lines of stars in M87 - which give us a gravitational mass, or emissions from the gas in motion around the central black hole.įor both our galaxy and M87, these two estimates were very different, with the gravitational estimates being about 50-90% larger than the gas estimates. Prior to the Event Horizon Telescope's first image, we had a number of different ways of measuring the masses of black holes. Gravitational dynamics of stars give good estimates for black hole masses observations of gas do not. Keck Observatory / UCLA Galactic Center GroupĢ. The results from the Event Horizon Telescope agree with the gravitational data, and not with the gas-based data. Gas measurements are systematically lower, while gravitational measurements are higher. You can also make measurements of the gas orbiting a black hole. That enables you to infer a mass for the central black hole, gravitationally. while M87 offers the prospect of observing absorption features from nearby stars. However, the observation also says nothing about dark matter, most modified gravity theories, quantum gravity, or what lies behind the event horizon. Those ideas are outside the scope of the Event Horizon Telescope's observations.Ī large slew of stars have been detected near the supermassive black hole at the Milky Way's core. This is, to the limits of the observations we've made, consistent with General Relativity. We know that the event horizon isn't a hard surface, as the infalling matter would have generated an infrared signature. We know there's a real event horizon and not a naked singularity, at least for many general classes of naked singularities. We now know this is a black hole and not a wormhole, at least for the most mainstream class of wormhole models. Well, this observation rules a bunch of them out. Even though General Relativity has passed every test we've thrown at it, there are no shortage of extensions, substitutes, or possible replacements. If you've ever seen an article with a title like, "theorist boldly claims that black holes don't exist" or "this new theory of gravity could upend Einstein," you've likely pieced together that physicists have no problem dreaming up alternative theories to the mainstream. This really is a black hole, as predicted by General Relativity.
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