Category: black hole

Ask Ethan: How Does The Event Horizon Telescop…

Ask Ethan: How Does The Event Horizon Telescope Act Like One Giant Mirror?

“I’m having difficulty understanding why the EHT array is considered as ONE telescope (which has the diameter of the earth).
When you consider the EHT as ONE radio telescope, I do understand that the angular resolution is very high due to the wavelength of the incoming signal and earth’s diameter. I also understand that time syncing is critical.
But it would help very much to explain why the diameter of the EHT is considered as ONE telescope, considering there are about 10 individual telescopes in the array.”

Humanity has imaged a black hole’s event horizon! It’s been less than a month since the news was announced, and it’s still hard to get over what a phenomenal achievement it was. It’s very difficult to conceive of how, though, we can treat 8 different telescopes and telescope arrays, all stitched together, as acting like a single giant mirror. But that’s exactly what the Event Horizon Telescope did. In fact, that’s what it needed to do, or it would never have been able to achieve the resolutions necessary to construct the first image of a black hole’s event horizon.

But we have it! We achieved it! And here’s the conceptual way you can understand it, even if you barely understand the way a single telescope works.

Ask Ethan: How Can A Black Hole’s Singul…

Ask Ethan: How Can A Black Hole’s Singularity Spin?

“How [is] angular momentum conserved when stars collapse to black holes? What [does] it means for a black hole to spin? What is actually spinning? How can a singularity spin? Is there a “speed limit” to this spin rate and how does the spin affect the size of the event horizon and the area immediately around it?”

When you think about a black hole, you probably think about an enormous amount of mass confined within an event horizon, collapsing down to a singular point at its center. And this is fine: this is just how Karl Schwarzschild conceived of it way back in 1916. But the stars and other forms of matter that potentially give rise to black holes cannot be point-like, since they all rotate. What happens to those rotational properties, or to angular momentum (which is always conserved), when they form a black hole? There are a lot of counterintuitive things that occur inside, and you’ll want to learn them all after reading this! 

In the aftermath of the Event Horizon Telescope’s big reveal, you just might join me in hoping Roy Kerr wins the Nobel Prize for his incredible 1963 paper.

Ask Ethan: How Can A Black Hole’s Singul…

Ask Ethan: How Can A Black Hole’s Singularity Spin?

“How [is] angular momentum conserved when stars collapse to black holes? What [does] it means for a black hole to spin? What is actually spinning? How can a singularity spin? Is there a “speed limit” to this spin rate and how does the spin affect the size of the event horizon and the area immediately around it?”

When you think about a black hole, you probably think about an enormous amount of mass confined within an event horizon, collapsing down to a singular point at its center. And this is fine: this is just how Karl Schwarzschild conceived of it way back in 1916. But the stars and other forms of matter that potentially give rise to black holes cannot be point-like, since they all rotate. What happens to those rotational properties, or to angular momentum (which is always conserved), when they form a black hole? There are a lot of counterintuitive things that occur inside, and you’ll want to learn them all after reading this! 

In the aftermath of the Event Horizon Telescope’s big reveal, you just might join me in hoping Roy Kerr wins the Nobel Prize for his incredible 1963 paper.

Ask Ethan: How Does Very-Long-Baseline Interfe…

Ask Ethan: How Does Very-Long-Baseline Interferometry Allow Us To Image A Black Hole?

“[The Event Horizon Telescope] uses VLBI. So what is interferometry and how was it employed by [the Event Horizon Telescope]? Seems like it was a key ingredient in producing the image of M87 but I have no idea how or why. Care to elucidate?”

If it were easy to network radio telescopes together across the world, we’d have produced an image of a black hole’s event horizon long ago. Well, it’s not easy at all, but it is at least possible! The technique that enabled it is known as VLBI: very-long-baseline interferometry. But there are some critical steps that aren’t very obvious that need to happen in order for this method to succeed. Remarkably, we learned how to do it and have successfully employed it, and the Event Horizon Telescope marks the first time we’ve ever been able to get an image with a telescope that’s effectively the size of planet Earth!

Come get the incredible science behind how the technique of VLBI enabled the Event Horizon Telescope to construct the first-ever image of a black hole’s event horizon!

Ask Ethan: How Does Very-Long-Baseline Interfe…

Ask Ethan: How Does Very-Long-Baseline Interferometry Allow Us To Image A Black Hole?

“[The Event Horizon Telescope] uses VLBI. So what is interferometry and how was it employed by [the Event Horizon Telescope]? Seems like it was a key ingredient in producing the image of M87 but I have no idea how or why. Care to elucidate?”

If it were easy to network radio telescopes together across the world, we’d have produced an image of a black hole’s event horizon long ago. Well, it’s not easy at all, but it is at least possible! The technique that enabled it is known as VLBI: very-long-baseline interferometry. But there are some critical steps that aren’t very obvious that need to happen in order for this method to succeed. Remarkably, we learned how to do it and have successfully employed it, and the Event Horizon Telescope marks the first time we’ve ever been able to get an image with a telescope that’s effectively the size of planet Earth!

Come get the incredible science behind how the technique of VLBI enabled the Event Horizon Telescope to construct the first-ever image of a black hole’s event horizon!

For those who want more precise information ab…

https://iopscience.iop.org/article/10.3847/2041-8213/ab0ec7

https://iopscience.iop.org/article/10.3847/2041-8213/ab0c96

https://iopscience.iop.org/article/10.3847/2041-8213/ab0c57

https://iopscience.iop.org/article/10.3847/2041-8213/ab0e85/meta

https://iopscience.iop.org/article/10.3847/2041-8213/ab0f43/meta

https://iopscience.iop.org/article/10.3847/2041-8213/ab1141/meta

For those who want more precise information ab…

https://iopscience.iop.org/article/10.3847/2041-8213/ab0ec7

https://iopscience.iop.org/article/10.3847/2041-8213/ab0c96

https://iopscience.iop.org/article/10.3847/2041-8213/ab0c57

https://iopscience.iop.org/article/10.3847/2041-8213/ab0e85/meta

https://iopscience.iop.org/article/10.3847/2041-8213/ab0f43/meta

https://iopscience.iop.org/article/10.3847/2041-8213/ab1141/meta

cosmicvastness: Astronomers Capture First I…

cosmicvastness:

Astronomers Capture First Image of a Black Hole

The Event Horizon Telescope (EHT) — a planet-scale array of eight ground-based radio telescopes forged through international collaboration — was designed to capture images of a black hole. Today, in coordinated press conferences across the globe, EHT researchers revealed that they have succeeded, unveiling the first direct visual evidence of a supermassive black hole and its shadow.

The image reveals the black hole at the centre of Messier 87, a massive galaxy in the nearby Virgo galaxy cluster. This black hole resides 55 million light-years from Earth and has a mass 6.5 billion times that of the Sun.

Supermassive black holes are relatively tiny astronomical objects — which has made them impossible to directly observe until now. As the size of a black hole’s event horizon is proportional to its mass, the more massive a black hole, the larger the shadow. Thanks to its enormous mass and relative proximity, M87’s black hole was predicted to be one of the largest viewable from Earth — making it a perfect target for the EHT. 

The shadow of a black hole is the closest we can come to an image of the black hole itself, a completely dark object from which light cannot escape. The black hole’s boundary — the event horizon from which the EHT takes its name — is around 2.5 times smaller than the shadow it casts and measures just under 40 billion km across.

Credit: ESO

I’m just mindblown.

cosmicvastness: Astronomers Capture First I…

cosmicvastness:

Astronomers Capture First Image of a Black Hole

The Event Horizon Telescope (EHT) — a planet-scale array of eight ground-based radio telescopes forged through international collaboration — was designed to capture images of a black hole. Today, in coordinated press conferences across the globe, EHT researchers revealed that they have succeeded, unveiling the first direct visual evidence of a supermassive black hole and its shadow.

The image reveals the black hole at the centre of Messier 87, a massive galaxy in the nearby Virgo galaxy cluster. This black hole resides 55 million light-years from Earth and has a mass 6.5 billion times that of the Sun.

Supermassive black holes are relatively tiny astronomical objects — which has made them impossible to directly observe until now. As the size of a black hole’s event horizon is proportional to its mass, the more massive a black hole, the larger the shadow. Thanks to its enormous mass and relative proximity, M87’s black hole was predicted to be one of the largest viewable from Earth — making it a perfect target for the EHT. 

The shadow of a black hole is the closest we can come to an image of the black hole itself, a completely dark object from which light cannot escape. The black hole’s boundary — the event horizon from which the EHT takes its name — is around 2.5 times smaller than the shadow it casts and measures just under 40 billion km across.

Credit: ESO

I’m just mindblown.

Black Holes Are Real And Spectacular, And So…

Black Holes Are Real And Spectacular, And So Are Their Event Horizons

“Originally estimated to be slightly larger than its M87 counterpart, the black hole at the center of the Milky Way — known as Sagittarius A* — has not yet had its event horizon imaged. When you observe the Universe, you don’t always get what you expect; sometimes, you get what it gives you. Instead, it was M87’s black hole that came through first, which was a much brighter and a much cleaner signal.

What we’ve found is spectacular. Those dark pixels at the center of the image are actually the silhouette of the event horizon itself. The light that we observe comes from the accelerated, heated matter around it, which must emit electromagnetic radiation. Where the matter exists, it emits radio waves, and the dark circle we see is where the background radio waves are blocked by the event horizon itself.”

We have an event horizon, folks! It wasn’t the one at the center of our galaxy that came through first, but rather the one at the center of Messier 87: a black hole over 1,000 times more massive, but some 2,000 times farther away, than the one contained in the Milky Way. This is an ultramassive black hole that’s almost the size of the entire Solar System, and its event horizon is real.

Come get the full story on what we know, now that we have our image, about black holes in the aftermath of the Event Horizon Telescope!