Sunday Nov 28, 2021

Imagining a camera shy black hole

Supermassive black holes they are greedy gravitational monsters weighing millions to billions of times the mass of our Sun. In fact, astronomers now offer that perhaps all the large galaxies in the observable Universe harbor one of these strange objects in their secret dark heart, and our Barred Spiral Milky Way itself is no exception. Our galaxy is haunted by its own dark-hungry heart, shrouded in a cloak of mystery, and has managed to keep its countless secrets well hidden from the prying eyes of curious astronomers. But despite their enormous mass and large numbers, supermassive black holes are notoriously camera-shy and have managed to escape being photographed.up to now. On April 10, 2019, the Event Horizon Telescope (EHT) revealed the first historical image of a supermassive black hole event horizon, which is the region beyond which not even light can escape the mighty and ruthless gravitational grip of the voracious dark beast. Although the existence of black holes has been theorized for more than two centuries, it was generally thought that it was impossible to observe them directly. Tea EHT is an international collaboration whose support in the US includes the National Science Foundation (NSF).

The recently revealed supermassive black hole weighs 6.5 trillion times the mass of our Sun. In contrast, the dark heart of our own galaxy is relatively light, at least by supermassive black hole standards, and weighs on the mother. millions (Opposite to trillion) times the solar mass. Our Milky Way’s resident gravitational beast has been named Sagittarius A * (pronounced Sagittarius – A-Star ), and is now a calm, elderly gravitational beast, only occasionally awakening from its peaceful slumber to nibble on a doomed wandering star or unfortunate gas cloud that has managed to travel too close to its jaws. When the Universe, our Galaxy and Sagittarius A * They were young, our resident beast glared at her quasar (the accretion disk surrounding a black hole), while he hungrily and carelessly dined on anything that managed to travel too close to where he was waiting. The ill-fated feast swirled down, down, into the waiting gravitational clutches of the then-young black hole, tumbling toward its inevitable doom from the surrounding dazzling accretion disk. Sagittarius A * he is considered to be asleep now, but from time to time he wakes up to dinner with the same greed as once, long ago, when he was a brilliant quasar illuminating the ancient Universe during its brand new youth. Sagittarius A * He is old and quiet now, but can still remember.

The camera-shy black hole, whose photo was taken recently, is located in the elliptical galaxy. Messier 87 (M87). An earlier image obtained from NASA Spitzer space telescope show everything M87 galaxy in infrared light. In contrast, the EHT The image was based on radio wavelengths to reveal the black hole’s secret shadow against a backdrop of high-energy material swirling around it.

The nature of the gravitational beast

Black holes come in different sizes. Some are of the supermassive type, residing in the center of galaxies, while those of “only” stellar mass they are much smaller. FOR stellar mass The black hole is born when a very massive star shatters in a supernova conflagration, thus ending its life as a Main sequence (burning hydrogen) star in the Hertzsprung-Russell diagram of stellar evolution There’s also intermediate mass black holes which are much heavier than their stellar mass brethren, but much less massive than their supermassive relatives. The gravitational collapse of a very massive star is a natural process. It is inevitable that when a heavy star reaches the end of that long stellar path, meaning that all of its energy sources have been exhausted, it will collapse under the ruthless crush of its own powerful gravity. This catastrophic event is heralded by the bright and glowing Grand finale of a supernova explosion. The most massive stars in the Universe die this way, eventually collapsing into a stellar-mass black hole.

Intermediate mass objects weigh hundreds of solar masses. Some astronomers have proposed that intermediate mass black holes collided and merged in the ancient Universe, thus creating the enormous supermassive variety that lurks at the hearts of galaxies.

Our Milky Way Sagittarius A * has much smaller company. Theoretical studies suggest that a large population of stellar-mass black holes, perhaps as many as 20,000, could be dancing around the resident dark heart of our own galaxy. A 2018 study, using data collected by NASA Chandra X-ray Observatory, indicates the existence of such a group of fascinating stellar-mass black holes in the heart of our Milky Way.

Despite their name, black holes are not just empty spaces. Squeeze enough matter into a small enough area and a black hole will always be born. However, black holes are really simple objects. A black hole of any mass has only three properties: electric charge, mass, and spin (angular momentum).

Many astronomers think that supermassive black holes already existed when the Universe was very young. During that ancient time, clouds of gas and unfortunate stars swirled into the fatal gravitational embrace of the black hole, never to return from the churning maelstrom that surrounded this voracious entity. As the captured material swirled toward its doom, it created a bright, violent storm of dazzling material around the black hole: the accretion disk (quasar). As the material got hotter and hotter, it released a violent radiation storm, particularly as it approached the event horizon–The point of no return.

In the 18th century, John Michell and Pierre-Simon Laplace considered the possibility that there Really be strange black holes in the Universe. In 1915, Albert Einstein, in his Theory of general relativity (1915) predicted the existence of objects with such strong gravitational fields that anything unlucky enough to travel too close to the hungry beast would be consumed. However, the idea that such strange objects could actually exist in the Cosmos seemed so outlandish at the time that Einstein rejected the idea, although his own calculations suggested otherwise.

In 1916, the physicist Karl Schwarzschild formulated the first modern solution to the Theory of general relativity describing a black hole. However, its interpretation as a region of space from which absolutely nothing could escape, as a result of the object’s powerful gravitational grip, was not properly understood until almost 50 years later. Until that time, black holes were thought to be mere mathematical oddities. It was not until the middle of the 20th century that theoretical work showed that these strange objects are a generic prediction of General relativity.

The dark heart of M87

Astronomers have been observing M87 for more than a century, and has been photographed by numerous NASA observatories, including the Hubble Space Telescope, the Chandra X-ray Observatory, and NuSTAR. In 1918, the American astronomer Heber Curtis (1872-1942) was the first to detect “a curious straight ray” extending from the center of the galaxy. This dazzling jet of high-energy material formed a rapidly spinning disk surrounding the black hole, which could be observed in multiple wavelengths of light, from radio waves to X-rays. interstellar medium, formed a shock wave that radiated in the infrared and radio wavelengths of the electromagnetic spectrum, but not in visible light. The Spitzer images show a shock wave that is more prominent than the plane itself.

The brightest jet is located to the right of the center of the galaxy and travels almost directly toward Earth. The glow of the jet is intensified both by its high speed in our direction and by its “relativistic effects” that arise because the jet is traveling at a speed close to the speed of light. The jet’s trajectory is slightly out of our line of sight with respect to the galaxy. This means that astronomers can observe part of the jet’s length. The shock wave begins around the point where the jet appears to curve downward, thus highlighting the regions where fast-moving particles collide with gas in the galaxy and thus slow it down.

In contrast, the second jet is moving away from Earth so rapidly that relativistic effects make it invisible at all wavelengths of the electromagnetic spectrum. However, the shock wave it creates in the interstellar medium can be observed from here.

The shock wave is located on the left side of M87 center, and looks like an inverted letter “C”. Although it cannot be seen in optical images, the lobe can be seen in radio waves, as seen in an image obtained from the Very Large Array of the National Radio Astronomy Observatory.

By combining observations obtained in infrared, radio waves, visible light, X-rays, and extremely energetic gamma rays, astronomers can study the physics of these powerful jets. Astronomers are still trying to get a solid theoretical understanding of how gas consumed by black holes forms jets that come out.

Infrared light at wavelengths of 3.6 and 4.5 microns is represented in blue and green in the revealing image of the dark shy heart from the camera. M87– thus revealing the distribution of stars. The powder features that glow at 8.0 microns are shown in red in the image. The image was obtained during From Spitzer “cold” initial mission.

Tea Event horizon telescope, that captured the historic image of a black hole, is a planetary-scale array made up of eight ground-based radio telescopes that were designed to image a camera-shy black hole. EHT Project Director Dr. Sheperd S. Doelman of the Harvard-Smithsonian Center for Astrophysics (CfA), annotated on an April 10, 2019 EHT press release that “We have taken the first photograph of a black hole. This is an extraordinary scientific feat accomplished by a team of more than 200 researchers.”

This historic scientific breakthrough was announced in a series of six articles published on April 10, 2019 in a special issue of The Astrophysics Journal Letters.

Dr. Doelman went on to comment that “We have accomplished something that was presumed impossible just a generation ago. Advances in technology, connections between the world’s best radio observatories, and innovative algorithms came together to open a whole new window on holes. blacks and the event horizon “.

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