Black holes are hard to find. Like, really hard to find. They are objects with such strong gravity that light can’t escape them, so we have to rely on clues from their surroundings to find them.
When a star weighing more than 20 times the Sun runs out of fuel, it collapses into a black hole. Scientists estimate that there are tens of millions of these black holes dotted around the Milky Way, but so far we’ve only identified a few dozen. Most of those are found with a star, each circling around the other. Another name for this kind of pair is a binary system.That’s because under the right circumstances material from the star can interact with the black hole, revealing its presence.
If the star and black hole orbit close enough, the black hole can pull material off of its stellar companion! As the material swirls toward the black hole, it forms a flat ring called an accretion disk. The disk gets very hot and can flare, causing bright bursts of light.
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V404 Cygni, depicted above, is a binary system where a star slightly smaller than the Sun orbits a black hole 10 times its mass in just 6.5 days. The black hole distorts the shape of the star and pulls material from its surface. In 2015, V404 Cygni came out of a 25-year slumber, erupting in X-rays that were initially detected by our Swift satellite. In fact, V404 Cygni erupts every couple of decades, perhaps driven by a build-up of material in the outer parts of the accretion disk that eventually rush in.
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In other cases, the black hole’s companion is a giant star with a strong stellar wind. This is like our Sun’s solar wind, but even more powerful. As material rushes out from the companion star, some of it is captured by the black hole’s gravity, forming an accretion disk.
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A famous example of a black hole powered by the wind of its companion is Cygnus X-1. In fact, it was the first object to be widely accepted as a black hole! Recent observations estimate that the black hole’s mass could be as much as 20 times that of our Sun. And its stellar companion is no slouch, either. It weighs in at about 40 times the Sun.
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We know our galaxy is peppered with black holes of many sizes with an array of stellar partners, but we’ve only found a small fraction of them so far. Scientists will keep studying the skies to add to our black hole menagerie.
Curious to learn more about black holes? Follow NASA Universe on Twitter and Facebook to keep up with the latest from our scientists and telescopes.
Take a good look: this is the black hole at the center of our galaxy.
In the inset image, gas in the glowing orange ring surrounds the black hole’s event horizon, a boundary from which nothing can escape. The ring is created by light bending in the intense gravity around Sagittarius A*, which has a mass some four million times greater than our Sun. This groundbreaking image of Sagittarius A* was taken by the Event Horizon Telescope team with data from telescopes around the world. After the EHT’s iconic image of M87*, released in 2019, this is only the second time a supermassive black hole has been directly observed with its shadow.
The wider look at the space around Sagittarius A* includes data contributed by several NASA missions. The orange specks and purple tendrils were captured in infrared light by the Hubble Space Telescope, and the blue clouds represent data from our orbiting Chandra X-ray Observatory.
On this day, 13 May 2021, local residents in Glasgow won the release of two people who had been detained by immigration officers by surrounding the vehicle and blockading it for several hours.
During Eid celebrations, Border Force snatched up the men and put them in a van. This was noticed by neighbours, who quickly surrounded the vehicle and contacted friends and local tenant and anti-eviction groups. One man climbed underneath the wheels of the van, where he remained for the duration of the subsequent events. One local resident, Lotte, told the Scotsman newspaper she wanted “to express my utter disgust at the brutal removal of my neighbours from their home”.
Soon the crowd had swelled to hundreds of people. Hundreds of police also came to the scene to try to clear the way for the immigration van to leave, but they were unable to dislodge the crowd. By the early evening, authorities relented and agreed to set the men free.
One of those detained, Lakhvir Singh, from India, issued a statement through a translator stating: “I’ve been astonished and overwhelmed by the support I’ve received from the people of Glasgow.”
May 10, 2022 - Protesters against the Sri Lanka government’s handling of the economic crisis pushed politician’s cars into the river, and have burned down at least 38 politiians’ homes. [video]
Fourth in a series I of comics about protesting safety tips I made with @this.is.ysabel . This one is about the dangers of police surveillance and how to avoid it if possible. Keep being safe when you go out. Don’t get snatched!
plenty of people have pointed out that you shouldnt bring your phone in general but also for the love of god DO NOT use signal, it was literally in large part funded by the open technology fund (which is itself a former program of radio free asia, which is IN TURN basically a CIA spinoff)
This blog is mostly so I can vent my feelings and share my interests. Other than that, I am nothing special.
If you don't like Left Wing political thought and philosophy, all things related to horror, the supernatural, the grotesque, guns or the strange, then get the fuck out. I just warned you.
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