Black holes can be more useful than we thought

Black holes – Giant space crabs can tear stars to pieces – but also shape the evolution of entire galaxies.

Black holes are the most fascinating and at the same time the most frightening phenomena in the universe. Their enormous gravity even prevents light from escaping from inside the opening, behind a so-called event horizon. Still, there is probably a black hole in the core of every massive galaxy. Indeed, these giant pits in space-time play an important role in the evolution of galaxies, and one of the criteria for galactic activity, for example, is considered to be that the black hole at its core throws matter into its environment.

Namely, black holes do not just attract particles and light strongly. They can also create jets that shoot plasma from the vicinity of a black hole so far that it flies up to the next galaxy.

Astronomers are trying to figure out why this is happening.

Galaxy thermostat


In principle, galaxies grow easily: new stars are formed as the gas cools. However, the existing research data are contradictory, as the most accurate calculations suggest that there should be more stars than there appear to be. So something happens along the way; some mechanism keeps star formation at a certain level as galaxies evolve. Black holes are believed to have their fingers in the game.

“Bidirectional plasma jets from black holes seem to act as a thermostat for the entire galaxy,” says Tuomas Savolainen, an Academy researcher at Aalto University.

“Many studies over the last twenty years suggest that these showers mechanically heat a gas that could otherwise become new stars. We still don’t know how these very narrow showers can distribute the energy generated by black holes over such a large area. ”

Exploring black holes is difficult. Because they absorb all the light, they cannot be seen in the same way as nearby planets or stars. Plasma jets are one noticeable consequence of the existence of black holes, but the areas where they develop are relatively small and incredibly far from the ground. For example, one of the nearest huge-sized and active black holes is located in the nearby M87 galaxy, more than 50 million light-years away.

Black hole
” Black holes – Giant space crabs can tear stars to pieces – but also shape the evolution of entire galaxies.”

“In order to distinguish the M87 shower in the images of the birth area, we need an observation device that is about a thousand times more accurate than the Hubble Space Telescope,” says Savolainen.

Therefore, researchers are forced to be creative. One of the ongoing projects is to combine the forces of numerous radio telescopes around the globe with a space-based radio telescope. The technology, called long-range interferometry, thus provides a detection device equivalent to a radio telescope with a resolution of up to 350,000 kilometers, which is thus larger than our planet. It has enabled the team to study the shower in the middle of the nearby Perseus A galaxy with unprecedented precision.

Black holes – The boundaries of vision stretch


Another important international collaboration project uses powerful, shorter-wavelength telescopes in the same way. The hope is to get the first image of the black hole in the center of our own galaxy, or really its shadow, visible in the light coming from behind the opening. This Event Horizon Telescope is so accurate that it could, for example, see a Domino biscuit on the Moon from the surface of the Earth.

“We are trying to stretch the boundaries of vision,” says Savolainen, who participates in both projects in his work at Aalto University’s Metsähovi Radio Observatory.

The uniquely accurate resolution is able to show where the plasma jets start. It’s also key when you want to see things you haven’t been able to see before. Such is, for example, the “shadow” of the black hole, i.e. the image of the event horizon formed by the gravitational lens phenomenon – a boundary beyond which there is no return.

Although the means of studying the universe are constantly evolving, as is the understanding of its phenomena, black holes have remained one of the great mysteries of astronomy.

“For example, we don’t yet fully understand how black holes give birth to these huge showers. However, we know that the magnetic field around the black hole plays a key role in the formation of the jet and that the energy of the jet possibly comes from the rotational movement of the jet, ”says Savolainen.

“By figuring out the trigger mechanism for the jets, we could find out why some black holes plunge plasma and others don’t. Above all, we would be able to explain how the heating of the galaxy is turned on and thereby understand the importance of jets for the evolution of the galaxy. ”

10 Amazing Facts About Black Holes

Imagine matter packed so densely that nothing can escape. Not a moon, not a planet and not even light. That’s what black holes are — a spot where gravity’s pull is huge, ending up being dangerous for anything that accidentally strays by. But how did black holes come to be, and why are they important? Below we have 10 facts about black holes — just a few tidbits about these fascinating objects.

Fact 1: You can’t directly see a black hole.

Because a black hole is indeed “black” — no light can escape from it — it’s impossible for us to sense the hole directly through our instruments, no matter what kind of electromagnetic radiation you use (light, X-rays, whatever.) The key is to look at the hole’s effects on the nearby environment, points out NASA. Say a star happens to get too close to the black hole, for example. The black hole naturally pulls on the star and rips it to shreds. When the matter from the star begins to bleed toward the black hole, it gets faster, gets hotter and glows brightly in X-rays.

Fact 2: Look out! Our Milky Way likely has a black hole.

A natural next question is given how dangerous a black hole is, is Earth in any imminent danger of getting swallowed? The answer is no, astronomers say, although there is probably a huge supermassive black hole lurking in the middle of our galaxy. Luckily, we’re nowhere near this monster — we are about two-thirds of the way out from the center, relative to the rest of our galaxy — but we can certainly observe its effects from afar. For example: the European Space Agency says it’s four million times more massive than our Sun, and that it’s surrounded by surprisingly hot gas.

Sagittarius A in infrared (red and yellow, from the Hubble Space Telescope) and X-ray (blue, from the Chandra space telescope). Credit: X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI

Fact 3: Dying stars create stellar black holes.

Say you have a star that’s about 20 times more massive than the Sun. Our Sun is going to end its life quietly; when its nuclear fuel burns out, it’ll slowly fade into a white dwarf. That’s not the case for far more massive stars. When those monsters run out of fuel, gravity will overwhelm the natural pressure the star maintains to keep its shape stable. When the pressure from nuclear reactions collapses, according to the Space Telescope Science Institute, gravity violently overwhelms and collapses the core and other layers are flung into space. This is called a supernova. The remaining core collapses into a singularity — a spot of infinite density and almost no volume. That’s another name for a black hole.

Fact 4: Black holes come in a range of sizes.

There are at least three types of black holes, NASA says, ranging from relative squeakers to those that dominate a galaxy’s center. Primordial black holes are the smallest kinds, and range in size from one atom’s size to a mountain’s mass. Stellar black holes, the most common type, are up to 20 times more massive than our own Sun and are likely sprinkled in the dozens within the Milky Way. And then there are the gargantuan ones in the centers of galaxies, called “supermassive black holes.” They’re each more than one million times more massive than the Sun. How these beasts formed is still being examined.

Fact 5: Weird time stuff happens around black holes.

This is best illustrated by one person (call them Unlucky) falling into a black hole while another person (call them Lucky) watches. From Lucky’s perspective, Unlucky’s time clock appears to be ticking slower and slower. This is in accordance with Einstein’s theory of general relativity, which (simply put) says that time is affected by how fast you go, when you’re at extreme speeds close to light. The black hole warps time and space so much that Unlucky’s time appears to be running slower. From Unlucky’s perspective, however, their clock is running normally and Lucky’s is running fast.

Fact 6: The first black hole wasn’t discovered until X-ray astronomy was used.

Cygnus X-1 was first found during balloon flights in the 1960s, but wasn’t identified as a black hole for about another decade. According to NASA, the black hole is 10 times more massive to the Sun. Nearby is a blue supergiant star that is about 20 times more massive than the Sun, which is bleeding due to the black hole and creating X-ray emissions.

Fact 7: The nearest black hole is likely not 1,600 light-years away.

An erroneous measurement of V4641 Sagitarii led to a slew of news reports a few years back saying that the nearest black hole to Earth is astoundingly close, just 1,600 light-years away. Not close enough to be considered dangerous, but way closer than thought. Further research, however, shows that the black hole is likely further away than that. Looking at the rotation of its companion star, among other factors, yielded a 2014 result of more than 20,000 light years.

Fact 8: We aren’t sure if wormholes exist.

A popular science-fiction topic concerns what happens if somebody falls into a black hole. Some people believe these objects are a sort of wormhole to other parts of the Universe, making faster-than-light travel possible. But as this Smithsonian Magazine article points out, anything is possible since we still have a lot to figure out about physics. “Since we do not yet have a theory that reliably unifies general relativity with quantum mechanics, we do not know of the entire zoo of possible spacetime structures that could accommodate wormholes,” said Abi Loeb, who is with the Harvard-Smithsonian Center for Astrophysics.

Diagram of a wormhole, or theoretical shortcut path between two locations in the universe.

Fact 9: Black holes are only dangerous if you get too close.

Like creatures behind a cage, it’s okay to observe a black hole if you stay away from its event horizon — think of it like the gravitational field of a planet. This zone is the point of no return, when you’re too close for any hope of rescue. But you can safely observe the black hole from outside of this arena. By extension, this means it’s likely impossible for a black hole to swallow up everything in the Universe (barring some sort of major revision to physics or understanding of our Cosmos, of course.)

Fact 10: Black holes are used all the time in science fiction.

There are so many films and movies using black holes, for example, that it’s impossible to list them all. Interstellar‘s journeys through the universe includes a close-up look at a black hole. Event Horizon explores the phenomenon of artificial black holes — something that is also discussed in the Star Trek universe. Black holes are also talked about in BattlestarGalactica, Stargate: SG1 and many, many other space shows.

Article source: https://www.aalto.fi/fi/uutiset/mustat-aukot-saattavat-olla-hyodyllisempia-kuin-luulimmekaan and https://www.universetoday.com/46687/black-hole-facts/

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