The first picture of a black hole opens a new era of astrophysics
This is what a black hole looks like.
A world-spanning network of telescopes called the Event Horizon Telescope zoomed in on the supermassive monster in the galaxy M87 to create this first-ever picture of a black hole.
“We have seen what we thought was unseeable. We have seen and taken a picture of a black hole,” Sheperd Doeleman, EHT Director and astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., said April 10 in Washington, D.C., at one of seven concurrent news conferences. The results were also published in six papers in the Astrophysical Journal Letters.
“We’ve been studying black holes so long, sometimes it’s easy to forget that none of us have actually seen one,” France Cordova, director of the National Science Foundation, said in the Washington, D.C., news conference. Seeing one “is a Herculean task,” she said.
That’s because black holes are notoriously hard to see. Their gravity is so extreme that nothing, not even light, can escape across the boundary at a black hole’s edge, known as the event horizon. But some black holes, especially supermassive ones dwelling in galaxies’ centers, stand out by voraciously accreting bright disks of gas and other material. The EHT image reveals the shadow of M87’s black hole on its accretion disk. Appearing as a fuzzy, asymmetrical ring, it unveils for the first time a dark abyss of one of the universe’s most mysterious objects.
“It’s been such a buildup,” Doeleman said. “It was just astonishment and wonder… to know that you’ve uncovered a part of the universe that was off limits to us.”
TheEvent Horizon Telescope is releasing its results on April 10th - including, we hope, the first picture of a black hole’s event horizon. The group has been analysing data for two years.
Video: “Observational appearance of an accretion disk in a General Relativistic Magnetohydrodynamics simulation at a radio wavelength.” - Dr. Hotaka Shiokawa, EHT media resources
During NASA’s Black Hole Week I saw a lot of social media posts, press releases, videos etc. that were not really correct.
One big issue with science communication about black holes is that while it has gotten good at dispelling the trivial myths (like “black holes suck everything into them and so you should be afraid Sgr A* will kill us all”) it has perpetuated other myths that require more detailed knowledge of general relativity and astronomy to debunk.
I thought it would be interesting to go over some of these misconceptions…
Seems like a good idea to reblog this post in case some astronomy social media managers say stuff freezes when it falls into a black hole again.
As far as the actual content of the original post, some things I would like to add:
A new misconception:
Myth: Hawking radiation comes from the event horizon of the black hole.
Reality: Hawking radiation comes from all the space-time around the black hole.
Hawking radiation is a very weak radiation all black holes are predicted to emit, and shrink down to nothing in the process. It is too weak and slow for us to detect for black holes of astrophysical size (i.e. those with the mass of stars) but if really tiny black holes exist, they could evaporate due to the radiation on timescales short enough for us to observe.
A common description of Hawking radiation in popularizations is that of matter and antimatter pairs of particles forming at the event horizon of the black hole, and one particle being sucked into the black hole and the other flying off into space as radiation. From this, one would expect the radiation to come from the event horizon, or very slightly above it.
In fact, Hawking radiation comes from a large region around the black hole, and it has the same wavelength as the size of the black hole itself. It’s like the black hole is surrounded in a diffuse bath of radiation that cannot be localized to it. This is because the particle pair description of Hawking radiation, while intuitive…is not how it actually is modeled or calculated in physics.
The actual process is too complicated for me to do calculations with (I’m a lowly astronomy & astrophysics PhD student, not a string theorist) but in general, space-time is filled with things called quantum fields. These are essentially more complex versions of stuff like the magnetic and electric fields (”classical fields”) that are more familiar. Their oscillations can appear to us as particles. When a black hole is present, it alters the possible ways the quantum fields can oscillate, like the presence of a hole in a drumskin changes the sounds the drumskin makes when you beat it. We see the new modes of oscillation as new particles.
…this is of course just an analogy, but it at least gives some idea of the physics involved.
Other notes:
-The field is leaning more and more to the idea that AGN feedback plays a major role in the quenching of star formation, at least for large spiral galaxies and the giant elliptical galaxies. That is, some form of “black holes kill galaxies” is looking more plausible as the years go by. Some form of AGN feedback appears to be necessary to get models of galaxy formation to work.
-Supermassive black holes may show jets up to higher luminosities (and so likely higher accretion rates) for their size than stellar black holes do. So the idea that quasars without visible jets lack them entirely is definitely not something that is proven at this time.
-Literally anything that has to do with what you would actually observe when you fall into a realistic astrophysical black hole that is rotating and accreting is full of disagreements between scientists. Other than that “you would die.” Remember that. “You would die.”
“As long as space is curved and you have mass, you can’t move through it without emitting gravitational radiation. In the most severe cases of all, it even affects the way you do addition. It took 100 years from the first prediction of gravitational waves until the first direct measurement of them, and that achievement has never looked more spectacular. As our observations improve, we’ll be able to pin down more subtle effects superimposed atop this simple approximation. But for now, enjoy the simplicity of the black hole math that everyone can do!”
Want to know how much mass gets turned into energy when two black holes merge? A whopping 10% of the smaller black hole’s mass.
What the Sight of a Black Hole Means to a Black Hole Physicist
The astrophysicist Janna Levin reflects on the newly unveiled, first-ever photograph of a black hole.
“At this historic moment, the world has paused to take in the sight of humanity’s first image of the strangest phenomenon in the known universe, a remarkable legacy of the general theory of relativity: a black hole. I am moved not just by the image; overwhelmingly I am moved by the significance of sharing this experience with strangers around the globe. I am moved by the image of a species looking at an image of a curious empty hole looming in space.
I am at the National Press Club, in Washington, D.C., a hive of excitement. Scientists with the Event Horizon Telescope aspired for years to take the first-ever picture of a supermassive black hole, so when they gathered journalists and scientists together today for a press conference, there wasn’t much doubt as to what we were here to see.
But still, there are surprises.
At the podium is Sheperd Doeleman, the director of the Event Horizon Telescope. He welcomes us, ‘black hole enthusiasts.’ I have the strongest memory of standing at the chalkboard in an otherwise empty classroom at the Massachusetts Institute of Technology with Shep, my funny friend with his funny, unmistakable, burnt-mahogany hair. Covered in chalk dust, we acquired the hard-earned mathematics of Albert Einstein’s theory of relativity.
We knew the words already, the standard lore: All forms of matter and energy bend space and time, and light and matter follow those curves. The words have to be taken on trust. But the mathematics we could acquire. It would belong to us. When Einstein conceived of relativity, he gave us a gift that has been passed from person to person around the world. Relativity, defying its name, is true for all of us.
Maybe my memory of that particular board is so crisp precisely because that moment defines the cusp between before and after acquiring relativity. Now I cannot imagine my own mind without it. Relativity permeates my thoughts so that I think in relativity the way writers think in their natural language. Since that time at MIT, Shep and I have both found our way via relativity to the most remarkable of its predictions, black holes.
Black holes were conceived of as a thought experiment, a fantastical imagining. Imagine matter crushed to a point. Don’t ask how. Just imagine that. While enlisted in the German army during World War I, Karl Schwarzschild discovered this possible solution to Einstein’s newly published theory of relativity, apocryphally between calculating ballistic trajectories from the trenches on the Russian front. Schwarzschild inferred that space-time effectively spills toward the crushed center. Racing at its absolute speed, even light gets dragged down the hole, casting a shadow on the sky. That shadow is the event horizon, the stark demarcation between the outside and anything with the misfortune to have fallen inside.
Einstein thought nature would protect us from the formation of black holes. To the contrary, nature makes them in abundance. When a dying star is heavy enough, gravity overcomes matter’s intrinsic resistance and the star collapses catastrophically. The event horizon is left behind as an archaeological record while the stellar material continues to fall inward to an unknown fate. In our own Milky Way galaxy there could be billions of black holes.
Supermassive black holes, millions or even billions of times the mass of the sun, anchor the centers of nearly all galaxies, though nobody yet knows how they formed or got so heavy. Maybe they formed from dead stars that merged and escalated in size, or maybe they directly collapsed out of more primordial material in a younger universe. However they formed, there are as many supermassive black holes as there are galaxies — hundreds of billions in the observable universe.
We had never seen a black hole before today. No telescope had ever taken a picture of one. We have indirectly inferred the presence of black holes when they’ve cannibalized companion stars, powered energetic jets in twisted magnetic fields, and captured stars in their orbit. We have even heard black holes collide and merge, ringing space-time like mallets on a drum.
We had never taken a direct picture of a black hole before because black holes are tiny, despite their dramatic reputation as weapons of mayhem and destruction (yes, the Nova film I hosted was called ‘Black Hole Apocalypse’). A black hole the mass of the sun would have an event horizon a mere 6 kilometers across. Compare that to the 1.4-million-kilometer breadth of the sun itself. The supermassive black hole at the center of the Milky Way, dubbed Sagittarius A*, is 4 million times the mass of the sun but only about 17 times wider.
Consider the challenge of capturing a portrait of an entirely dark object only 17 times the width of an ordinary star at a distance of 26,000 light-years. Resolving an image of Sagittarius A* is comparable to resolving the image of a piece of fruit on the moon.
To resolve such a minuscule image requires a telescope the size of the entire Earth. Since those days in that chalk-dusted classroom at MIT, my funny, utterly unconventional friend has been determined to capture the image of a supermassive black hole all the same.
During our years in graduate school, Shep’s hair was an allegory for his mind — wild and spirited. I admired the freedom I sensed in the way he thought, always forging unexpected connections, sometimes at the expense of the required lesson. His shocked eyes would warn me that a crazy idea had struck him just at that precise moment, as though he was as surprised as I was by the thought.
The Event Horizon Telescope is a testament to bold ideas, as well as scientific ingenuity and collaboration. Exploiting large radio telescopes around the globe — relying on the newest, most sophisticated observatories and reviving some that were nearly defunct — EHT became a composite telescope the size of the Earth. As the planet spins and orbits, the target black holes rise into the field of view of component telescopes around the planet. To render a precise image, the telescopes need to operate as one, which involves sensitive time corrections so that one global eye looks toward the black hole.
Combining telescopes for better resolution was the basis of Shep’s doctoral thesis in the ’90s. By 2008, he led a small team that imaged structures comparable in size to nearby supermassive black holes. That proof of concept drove the EHT project, whose team was now confident that the required resolution was in reach. In the decade since, EHT had to address challenges the data posed and advance technologically, and Shep is quick to credit the international team for their stamina and for the cleverness of their collective contributions.
Our supermassive black hole, Sagittarius A*, became the obvious target to pursue. Despite the abundance of supermassive black holes in galaxies, all others are too far away to resolve even with a telescope the size of the Earth. There is one exception. Messier 87, or M87, is an enormous elliptical galaxy 55 million light-years away that is known to harbor a staggering supermassive black hole somewhere between 3.5 billion and 7.2 billion times the mass of the sun. At the small end of that range, M87 would be an impossible target for EHT. At the high end, it is possibly suitable. So M87 became a secondary target in the heated pursuit of Sagittarius A*.
A black hole against the dark backdrop of empty space would be truly invisible. Sagittarius A* and M87 are helpfully illuminated by debris caught in hot disks orbiting very near their event horizons. The path of the light from the luminous orbiting material is bent along the curved space so that even light behind a black hole gets redirected our way. The disk appears to surround the black hole, allowing for a bright contrast against which its shadow is visible.
EHT actually sees an area slightly outside the event horizon itself — a region defined by the location closest to the black hole where a beam of light could orbit on a circle, known as the ‘last photon orbit.’ (Were you to float there, you could see light reflected off the back of your head after completing a round trip. Or, if you turned around quickly enough, you might see your own face.) Closer than that, all the light falls in.
We are gathered here, black hole theorists and observers, journalists and friends, in this room together to share an image we could already pretty well imagine and were excited to celebrate. But this was the surprise on hearing the announcement: It’s not Sagittarius A* they saw. It’s not our black hole. It’s M87!
The image is unmistakable — a dark shadow the size of our solar system, enveloped by a bright, beautiful blob.
While the scientific implications will take time to unpack, some of the anthropological impact feels immediate. The light EHT collected from M87 headed our way 55 million years ago. Over those eons, we emerged on Earth along with our myths, differentiated cultures, ideologies, languages and varied beliefs. Looking at M87, I am reminded that scientific discoveries transcend those differences. We are all under the same sky, all of us bound to this pale blue dot, floating in the sparse local territory of our solar system’s celestial bodies, under the warmth of our yellow sun, in a sparse sea of stars, in orbit around a supermassive black hole at the center of our luminous galaxy.
When asked his thoughts at the moment he first saw the image of the black hole in M87, Shep replied, ‘We saw something so true.’ And it’s true for all of us.”
Hello! I’ve invented a system of space-themed xenic alignments that I’m calling the Cosmoic Alignments. I wanted to keep them completely independent of male, female, masc, and fem as well as give them a sort of abstract feel. I’ll list the alignments below, and then provide their flags in a Read More.
I want to also note that these can be used by any human or nonhuman, whether they have no gender or many genders. They also don’t have to be xenogender in order to identify with these.
Void-aligned - A formless, dark, and frigid alignment. May be unaligned or reject alignment altogether. Associated with black holes and deep space.
Constellation-aligned - A cold, multifaceted alignment that is complex and solid. May feel as though the individual parts of the alignment make up one larger alignment identity. Associated with starlight and astrology.
Nebula-aligned - A fluid, colorful, and bright alignment that floats slowly through the cold void of space. May often feel cloudy or intangible. Associated with the alignment of supernova and with stars.
Aurora-aligned - A fluctuating, colorful, and bright alignment that swirls through the temperate atmosphere. Associated with solar winds, magnetic fields, and planet Earth.
Stellar-aligned - A large, hot, and bright alignment with a fixed course through space. May be loud or boisterous. Associated with light and solar eclipses.
Supernova-aligned - A huge and red-hot alignment that seems to expand rapidly in all directions. May feel like it’s burning up other alignments around it. Associated with stars.
Planet-aligned - A stable, solid, and warm alignment thriving with liveliness. May align with both sunlight or darkness. Associated with weather patterns and gravitational forces.
Lunar-aligned - A quiet, slow, and cold alignment with a fixed course through space. May align with softness or grace. Associated with water and lunar eclipses.
Asteroid-aligned - An erratic and unpredictable alignment that is cold. May feel like it’s far away from other alignments.
Singularity-aligned - A small and enigmatic red-hot alignment that has the potential to be something bigger. May indicate questioning alignment rather than being sure.
Quantum-aligned - A paradoxical alignment that is both known and unknown, present and absent. May be complex or simple, and may overlap with many other alignments or none at all.
Language to use: “I am a cosmoic demiboy. My alignment is lunar. I am a lunar-aligned demiboy.”
** All flags are below the cut. They’re in order from top to bottom. **
While studying intergalactic gas, astrophysicist and Kavli Prize winner Andrew Fabian detected the deepest sound ever recorded in the universe and tracked down its origin: a highly pressurized black hole!
We’ve Been Underestimating How Many Black Hole Collisions Are Terrorising The Universe
Staring into the void.
By David Nield
Astronomers have found what looks to a fresh trove of supermassive black hole pairs, increasing the number of known pairs by about 50 percent, after new image analysis techniques were used to study two of our most detailed sky surveys.
Finding these black hole pairs is crucial to understanding more about how they form and how galaxies eventually collide, with the new findings giving astronomers five new pairs to analyse.
Supernova Fail: Giant Dying Star Collapses Straight into Black Hole
By Elizabeth Howell
It appears the path to becoming a black hole is more complex than astronomers thought. Rather than exploding into a supernova before collapsing into a black hole, as expected, one giant star skipped the pyrotechnics and went straight to the collapse.
This so-called “massive fail,” spotted in a nearby galaxy, could explain why so few massive stars have been observed going supernova, researchers conducting a new study explained. As many as 30 percent of these massive stars may instead quietly collapse into a black hole.
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.
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.
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.
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.
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.
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