Do all black holes work the same, regardless of their size?
We tend to think of black holes as giant giants that eat light. But even supermassive black holes, the gravitational sinks that exist at the center of galaxies, come in a variety of sizes. Take M87 *, which is located in the center of the Messier 87 galaxy. It is about 6 billion times more massive than our sun. Or you could look at Sgr A *, which is in the center of the Milky Way and is just (only!) 4 million times more massive than the sun. Small, when it comes to supermassive black holes.
The incredible size of M87 * was in part why it was a good candidate for the Event Horizon Telescope to capture.. That feat, accomplished in 2017, was immediately hailed as a breakthrough in astrophysics when it was revealed to the world in 2019. The portrait was the culminating achievement of years of work using a handful of observatories around the world that essentially functioned as a single planet. -size telescope. The advance allowed scientists to see the shadow cast by Messier 87’s dark heart.
But that was just the beginning.
Astrophysicists weren’t going to stop at just one black hole. They then turned their attention to another supermassive black hole, about 100 times smaller than M87 *, located at the center of the nearby galaxy known as Centaurus A. Using the same technique that captured M87 *, astrophysicists have now been able to image of a powerful jet of matter shooting out of Centaur A’s black hole in ultra-high resolution, revealing more about how these puzzling phenomena arise.
The details were published in the journal Nature Astronomy on Monday.
“The main goal of the EHT is to image black holes,” says Michael Janssen, an astrophysicist at the Max Planck Institute for Radio Astronomy in Bonn, Germany, and lead author of the study. “But the jets are naturally launched by the black holes we are studying. So, to fully understand black holes, we also need to understand these jets and how they are produced.”
Cosmic jets are– including M87 * – and are essentially runaway plasma charges spewing from the accretion disk of a rapidly spinning black hole.
“These narrow, focused beams of plasma carry energy on small scales close to the black hole (the size of which is smaller than that of our solar system) and deposit it into the surrounding environment at much larger scales,” says James Miller-Jones, an astrophysicist at Curtin University of Australia and a member of the International Center for Radio Astronomy Research (ICRAR). The jets, Miller-Jones says, can affect the evolution of the galaxy and galaxy cluster, so astronomers are eager to understand them better.
Janssen and his colleagues are one such group of astronomers. They wanted to zoom in on the jets to see how they work near the black hole. The EHT made it possible.
The EHT consists of eight observatories from around the world and uses a technique known as very long baseline interferometry, or VLBI. In general, Janssen notes, larger telescopes provide sharper images, but are only big enough to build. Rather than manufacturing a monolithic telescope, the EHT links telescopes from all over the world virtually, providing a resolution equivalent to a single telescope “thousands of kilometers in size.”
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With it, the team could focus on the jet in Centaurus A and see it more clearly than ever. It also allowed them to image the jet very close to the black hole.
“We can study this jet with a sub-day resolution of light, which has never been achieved before,” says Janssen. The EHT observations allow the team to see about 0.6 light days away from the black hole, which sounds small but equates to about 2.5 times the distance between the sun and Pluto, a lazy 9.6 billion miles. .
By looking at the heart of Centaurus A and comparing their observations with theoretical models, the team finds that the jet from the black hole has brighter edges and looks strikingly similar to the one created by M87 *. That’s critical because it brings us back to our initial question: Do all black holes work the same, regardless of their size?
The Centaurus A jet suggests that this could be the case. That’s important for two reasons: It’s consistent with Albert Einstein’s theory of general relativity, and it’s “the claim that the fundamental properties of jets depend on the mass of the black hole that launches them,” says Miller-Jones.
He adds that this scale could be valid for much, much smaller black holes, with masses only 10 to 100 times that of the sun. We can’t test these tiny black holes because they are too small, but by studying their monstrous cousins, we are unraveling some of the mysteries of the most enigmatic giants in the universe.