First image of the black hole at the center of the Milky Way. This is the first image of Sagittarius A* (or Sgr A* for short), the supermassive black hole at the centre of our galaxy. It’s the first direct visual evidence of the presence of this black hole. It was captured by the Event Horizon Telescope (EHT), an array which linked together eight existing radio observatories across the planet to form a single “Earth-sized” virtual telescope. The telescope is named after the “event horizon”, the boundary of the black hole beyond which no light can escape. Although we cannot see the event horizon itself, because it cannot emit light, glowing gas orbiting around the black hole reveals a telltale signature: a dark central region (called a “shadow”) surrounded by a bright ring-like structure. The new view captures light bent by the powerful gravity of the black hole, which is four million times more massive than our Sun. The image of the Sgr A* black hole is an average of the different images the EHT Collaboration has extracted from its 2017 observations. Credit: EHT Collaboration

by Amy C. Oliver, National Radio Astronomy Observatory

MAY 12, 2022

At simultaneous press conferences around the world, including at a National Science Foundation-sponsored press conference at the U.S. National Press Club in Washington, D.C., astronomers have unveiled the first image of the supermassive black hole at the center of our own Milky Way galaxy. This result provides overwhelming evidence that the object is indeed a black hole and yields valuable clues about the workings of such giants, which are thought to reside at the center of most galaxies. The image was produced by a global research team called the Event Horizon Telescope (EHT) Collaboration, using observations from a worldwide network of radio telescopes.

See full text

The full article

From outside a black hole, all the infalling matter will emit light and always is visible, while... [+] ANDREW HAMILTON, JILA, UNIVERSITY OF COLORADO

Ethan Siegel   Jun 1, 2019,

There are many terrifying ways that the Universe can destroy something. In space, if you tried to hold your breath, your lungs would explode; if you exhaled every molecule of air instead, you'd black out within seconds. In some locations, you'd freeze solid as the heat was sucked out of your body; in others it's so hot that your atoms would turn into a plasma. But of all the ways the Universe has to dispose of someone, I can think of none more fascinating than to send someone inside a black hole. So does Event Horizon Telescope scientist Heino Falcke, who asks:

[W]hat is it like to be/fall inside a rotating black hole? This is not observable, but calculable... I have talked with various people who have done these calculations, but I am getting old and keep forgetting things.

It's a tremendously interesting question, and one that science can answer. Let's find out.

According to our theory of gravity, Einstein's General Relativity, there are only three things that determine the properties of a black hole. They are the following:

See full text

Can a fluid analogue of a black hole point physicists toward the theory of quantum gravity, or is it a red herring?

NATALIE WOLCHOVER  --  SCIENCE

IN A 1972 lecture at the University of Oxford, a young physicist named William Unruh asked the audience to imagine a fish screaming as it plunges over a waterfall. The water falls so fast in this fictitious cascade that it exceeds the speed of sound at a certain point along the way. After the fish tumbles past this point, the water sweeps its screams downward faster than the sound waves can travel up, and the fish can no longer be heard by its friends in the river above.

Something similar happens, Unruh explained, when you fall into a black hole. As you approach one of these super-dense objects, the fabric of space and time becomes increasingly curved—equivalent to strengthening gravity, according to Albert Einstein’s general theory of relativity. At a point of no return known as the “event horizon,” the space-time curvature becomes so steep that signals can no longer climb to the outside world. Within the event horizon, even light is held captive by the black hole’s gravity, rendering black holes invisible.

See full text

Wormholes are fascinating (but theoretical) cosmological objects that can connect two distant regions of the universe. They would allow one to create “shortcuts” through space in order to travel vast distances in a shorter period of time. They are predicted by the general Theory of Relativity, and are what Einstein referred to as “bridges” through space-time. Wormholes are mathematically predicted, if not proven, and a new study illustrates how scientists have taken these theoretical anomalies – which many physicists believe to be real – and created one for them.

Researchers in Spain, from the physics department at the Autonomous University of Barcelona, have actually created a magnetic wormhole in a lab that tunnels a magnetic field through space.
Using matematerials and metasurfaces, our wormhole transfers the magnetic field from one point in space to another through a path that is magnetically undetectable. We experimentally show that the magnetic field from a source at one end of the wormhole appears at the other end as an isolated magnetic monopolar field, creating the illusion of a magnetic field propagating through a tunnel outside the 3D space.

See full text

 A view of the M87 supermassive black hole in polarised light  EHT Collaboration/ESO

The first picture of a black hole’s shadow just got even more interesting. The Event Horizon Telescope (EHT) collaboration released the first direct image of a black hole in 2019, and while the picture on its own was impressive, it wasn’t the scientific smorgasbord some had hoped for. Now, researchers have added polarised light to the picture, giving us an idea of how magnetic fields around a supermassive black hole create powerful jets of matter.

“It was not a lot of information about the actual physics of the gas around the black hole,” says Sara Issaoun, an EHT team member at Radboud University in the Netherlands. “Looking at it in polarised light told us information about the magnetic field of the black hole.”

Read more

Journal references

The globular cluster NGC 6397 is one of the closest to Earth at a distance of 7,800 light years. Analysis of multiple observations over several years with the Hubble Space Telescope reveals the gravitational effects of multiple stellar-mass black holes. Image: NASA, ESA, T. Brown, S. Casertano, and J. Anderson (STScI)

11 February 2021 Astronomy Now

Black holes are thought to range between two extremes: from stellar-mass black holes that form when single, massive stars collapse to the supermassive behemoths millions to billions of times the mass of the Sun. Intermediate-mass holes, with the gravitational heft of hundreds to tens of thousands of stars, are thought to bridge the gap between the two extremes, but only a few candidates have been identified to date.

Likely habitats for intermediate black holes are the cores of globular clusters, the concentrated assemblies of ancient stars that are nearly as old as the cosmos. Researchers using the Hubble Space Telescope observed one of the closest globulars to Earth – NGC 6397 – looking for stellar motions that might indicate the gravitational influence of an intermediate black hole.

Instead, they were surprised to find signs of multiple stellar-mass black holes.

“We found very strong evidence for an invisible mass in the dense core of the globular cluster, but we were surprised to find that this extra mass is not ‘point-like’ but extended to a few percent of the size of the cluster,” said Eduardo Vitral of the Paris Institute of Astrophysics.

See full text

Science and Nature  7.2.2021

You don’t have to know a whole lot about science to know that black holes normally suck things in, not spew things out. But NASA detected something mighty bizarre at the supermassive black hole Markarian 335. Two of NASA’s space telescopes, including the Nuclear Spectroscopic Telescope Array (NuSTAR), amazingly observed a black hole’s corona “launched” away from the supermassive black hole.

Then an enormous pulse of X-ray energy spewed out. This kind of phenomena has never been observed before.
“This is the first time we have been able to link the launching of the corona to a flare. This will help us comprehend how supermassive black holes power some of the brightest objects in the cosmos.” Dan Wilkins, of Saint Mary’s University, said. This is one of the most important discoveries so far.

See full text

MICHELLE STARR 18 DECEMBER 2020

The Universe is full of galaxy clusters, but Abell 2261 is in a class of its own. In the galaxy in the centre of the cluster, where there should be one of the biggest supermassive black holes in the Universe, astronomers have been able to find no trace of such an object.

And a new search has only made the absence more puzzling: if the supermassive black hole got yeeted out into space, it should have left evidence of its passage. But there's no sign of it in the material surrounding the galactic centre, either.

But this means that constraints can be placed on what the supermassive black hole - if it is there, evading detection - is doing.

Galaxy clusters are the largest known gravitationally bound structures in the Universe. Typically, they're groups of hundreds to thousands of galaxies that are bound together, with one huge, abnormally bright galaxy at or close the centre, known as the brightest cluster galaxy (BCG).

But even among BCGs, Abell 2261's BCG (named, in fact, A2261-BCG, and located about 2.7 billion light-years away) stands out. It's about a million light-years across - up to to 10 times the size of the Milky Way galaxy - and it has a huge, puffy core 10,000 light-years across, the largest galactic core ever seen.

See full text

This year's Nobel Prize in Physics was awarded to Roger Penrose, Reinhard Genzel and Andrea Ghez.

By Emma Reynolds and Katie Hunt, CNN, October 6, 2020

(CNN)The 2020 Nobel Prize in Physics has been awarded to scientists Roger Penrose, Reinhard Genzel and Andrea Ghez for their discoveries about black holes.

Göran K. Hansson, secretary for the Royal Swedish Academy of Sciences, said at Tuesday's ceremony in Stockholm that this year's prize was about "the darkest secrets of universe."

Penrose, a professor at the University of Oxford who worked with Stephen Hawking, was awarded half of the prize "for the discovery that black hole formation is a robust prediction of the general theory of relativity." The other half was awarded jointly to Genzel and Ghez "for the discovery of a supermassive compact object at the center of our galaxy."

"Penrose, Genzel and Ghez together showed us that black holes are awe-inspiring, mathematically sublime, and actually exist," Tom McLeish, professor of natural philosophy at the University of York, told the Science Media Centre in London.

Ghez, born in New York City and a professor at the University of California, Los Angeles, is only the fourth woman to win a Nobel physics prize. It was awarded to a woman for the first time in 55 years in 2018, when Donna Strickland won for groundbreaking inventions in the field of laser physics.

See full text

From the Royal Swedish Academy of Sciences

1  Original announcement

2  Scientific Background

3  Popular Science  Background

Snapshots of the appearance of M87 *, obtained with images and geometrical models and the EHT array between 2009 and 2017. The diameter of the rings is the same, but the location of the bright side varies. - (Image Credit: M. Wielgus, D. Pesce & the EHT Collaboration)

September 23, 2020

The Event Horizon Telescope is an array of telescopes that uses a technique called Very Long Baseline Interferometry (VLBI) to form a virtual radio telescope with a dish diameter similar to the size of Earth.

In the period between 2009-2013, M87* (the supermassive black hole in the galaxy M87) was observed with prototype EHT telescopes, at four different sites. Eventually, the entire EHT array came into operation in 2017, with seven telescopes located in five locations around the Earth.

Although the observations from 2009-2013 contained much less data than those from 2017 (lacking the capacity to provide a picture of the black hole at that point in time), the EHT team was able to identify changes in the appearance of M87* between 2009 and 2017 using statistical models.

The researchers concluded that the diameter of the black hole's shadow remains consistent with the predictions of Einstein's general theory of relativity for black holes of 6.5 billion solar masses. But they also found something unexpected: the crescent-shaped ring of hot plasma around M87* wobbles! It is the first time astronomers have glimpsed the dynamic accretion structure so close to the event horizon of a black hole, where gravity is extreme.

See full text

Link to the publication 

See also

An artist’s conception of two black holes entwined in a gravitational tango. Credit: NASA/JPL-Caltech/SwRI/MSSS/Christopher Go

Do supermassive black holes have friends? The nature of galaxy formation suggests that the answer is yes, and in fact, pairs of supermassive black holes should be common in the universe.

I am an astrophysicist and am interested in a wide range of theoretical problems in astrophysics, from the formation of the very first galaxies to the gravitational interactions of black holes, stars and even planets. Black holes are intriguing systems, and supermassive black holes and the dense stellar environments that surround them represent one of the most extreme places in our universe.

See full text

A black hole (one illustrated) with a mass equal to about 68 suns has been found in the Milky Way, researchers say. That dark mass is much heavier than other similar black holes. (NAOJ)

By Christopher Crockett 28.11.2019

A heavyweight black hole in our galaxy has some explaining to do.

With a mass of about 68 suns, it is far heftier than other stellar-mass black holes (those with masses below about 100 suns) in and around the Milky Way, scientists say. That’s not just a record, it’s also a conundrum. According to theory, black holes in our galaxy that form from the explosive deaths of massive stars — as this one likely did — shouldn’t be heavier than about 25 suns.

The black hole is locked in orbit with a young blue star dubbed LB-1, which sits about 13,800 light-years away in the constellation Gemini, researchers found. Combing through data from the LAMOST telescope in China, Jifeng Liu, an astrophysicist at the Chinese Academy of Sciences in Beijing, and colleagues noticed that LB-1 repeatedly moves toward and away from Earth with great speed — a sign that the star orbits something massive.

With additional observations from telescopes in Hawaii and the Canary Islands, the team mapped out the orbit and deduced that the star gets whipped around by a dark mass roughly 68 times as massive as the sun. Only a black hole fits that description, the team reports November 27 in Nature.

See full text

Scientists have obtained the first image of a black hole, using Event Horizon Telescope observations of the center of the galaxy M87. The image shows a bright ring formed as light bends in the intense gravity around a black hole that is 6.5 billion times more massive than the Sun. This long-sought image provides the strongest evidence to date for the existence of supermassive black holes and opens a new window onto the study of black holes, their event horizons, and gravity. Credit: Event Horizon Telescope Collaboration

https://www.youtube.com/watch?v=3QEPzP58neg&feature=youtu.be

2020 Breakthrough Prize in Fundamental Physics

The Event Horizon Telescope Collaboration

Collaboration Director Shep Doeleman of the Harvard-Smithsonian Center for Astrophysics will accept on behalf the collaboration. The $3 million prize will be shared equally with 347 scientists co-authoring any of the six papers published by the EHT on April 10, 2019, which can be found here. The names are also listed at the bottom of this page.
Citation: For the first image of a supermassive black hole, taken by means of an Earth-sized alliance of telescopes.
Description: Using eight sensitive radio telescopes strategically positioned around the world in Antarctica, Chile, Mexico, Hawaii, Arizona and Spain, a global collaboration of scientists at 60 institutions operating in 20 countries and regions captured an image of a black hole for the first time. By synchronizing each telescope using a network of atomic clocks, the team created a virtual telescope as large as the Earth, with a resolving power never before achieved from the surface of our planet. One of their first targets was the supermassive black hole at the center of the Messier 87 galaxy – its mass equivalent to 6.5 billion suns. After painstakingly analyzing the data with novel algorithms and techniques, the team produced an image of this galactic monster, silhouetted against hot gas swirling around the black hole, that matched expectations from Einstein's theory of gravity: a bright ring marking the point where light orbits the black hole, surrounding a dark region where light cannot escape the black hole's gravitational pull.

See more

BLAST FROM COLLAPSE A collapsar occurs when a massive, spinning star collapses into a black hole, powering a blast of light known as a long gamma ray burst (illustrated) and exploding the star’s outer layers.

Spinning stellar objects collapsing into black holes could help explain heavy elements’ origins
BY EMILY CONOVER  MAY 8, 2019

The gold in your favorite jewelry could be the messy leftovers from a newborn black hole’s first meal.

Heavy elements such as gold, platinum and uranium might be formed in collapsars — rapidly spinning, massive stars that collapse into black holes as their outer layers explode in a rare type of supernova. A disk of material, swirling around the new black hole as it feeds, can create the conditions necessary for the astronomical alchemy, scientists report online May 8 in Nature.

“Black holes in these extreme environments are fussy eaters,” says astrophysicist Brian Metzger of Columbia University, a coauthor of the study. They can gulp down only so much matter at a time, and what they don’t swallow blows off in a wind that is rich in neutrons — just the right conditions for the creation of heavy elements, computer simulations reveal.

Astronomers have long puzzled over the origins of the heaviest elements in the universe. Lighter elements like carbon, oxygen and iron form inside stars, before being spewed out in stellar explosions called supernovas. But to create elements further down the periodic table, an extreme environment densely packed with neutrons is required. That’s where a chain of reactions known as the r-process can occur, in which atomic nuclei rapidly absorb neutrons and undergo radioactive decay to create new elements.

See full text

EHT images of M87 on four different observing nights. In each panel, the white circle shows the resolution of the EHT. All four images are dominated by a bright ring with enhanced emission in the south. 

The Astrophysical Journal Letters

Shep Doeleman (EHT Director) on behalf of the EHT Collaboration -- April 2019

This Focus Issue shows ultra-high angular resolution images of radio emission from the supermassive black hole believed to lie at the heart of galaxy M87 (Figure 1). A defining feature of the images is an irregular but clear bright ring, whose size and shape agree closely with the expected lensed photon orbit of a 6.5 billion solar mass black hole. Soon after Einstein introduced general relativity, theorists derived the full analytic form of the photon orbit, and first simulated its lensed appearance in the 1970s. By the 2000s, it was possible to sketch the "shadow" formed in the image when synchrotron emission from an optically thin accretion flow is lensed in the black hole's gravity. During this time, observational evidence began to build for the existence of black holes at the centers of active galaxies, and in our own Milky Way. In particular, a steady progression in radio astronomy enabled very long baseline interferometry (VLBI) observations at ever-shorter wavelengths, targeting supermassive black holes with the largest apparent event horizons: M87, and Sgr A* in the Galactic Center. The compact sizes of these two sources were confirmed by studies at 1.3mm, first exploiting baselines that ran from Hawai'i to the mainland US, then with increased resolution on baselines to Spain and Chile.

See full text