Category: event horizon telescope

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.

The Two Scientific Ways We Can Improve Our Ima…

The Two Scientific Ways We Can Improve Our Images Of Event Horizons

“By properly equipping and calibrating each participating telescope, the resolution sharpens, replacing an individual telescope’s diameter with the array’s maximum separation distance. At the Event Horizon Telescope’s maximum baseline and wavelength capabilities, it will attain resolutions of ~15 μas: a 50% improvement over the first observations. Currently limited to 345 GHz, we could strive for higher radio frequencies like 1-to-1.6 THz, progressing our resolution to just ~3-to-5 μas. But the greatest enhancement would come from extending our radio telescope array into space.”

It’s absolutely incredible that we’ve got our first image of a black hole’s event horizon, and a monumental achievement for science. But like all scientists, opening the door to a new “first” only increases our drive to surpass what we’ve accomplished and improve our capabilities beyond anything we’ve achieved before. For an event horizon, that means higher resolutions and sharper images, and we have two scientific ways to get there: probing higher frequencies and extending the length of our baseline to beyond the limits of planet Earth.

Both of these are technologically possible, and will likely, over the coming years and decades, be how we push past our scientific limits. Come learn how.

The Two Scientific Ways We Can Improve Our Ima…

The Two Scientific Ways We Can Improve Our Images Of Event Horizons

“By properly equipping and calibrating each participating telescope, the resolution sharpens, replacing an individual telescope’s diameter with the array’s maximum separation distance. At the Event Horizon Telescope’s maximum baseline and wavelength capabilities, it will attain resolutions of ~15 μas: a 50% improvement over the first observations. Currently limited to 345 GHz, we could strive for higher radio frequencies like 1-to-1.6 THz, progressing our resolution to just ~3-to-5 μas. But the greatest enhancement would come from extending our radio telescope array into space.”

It’s absolutely incredible that we’ve got our first image of a black hole’s event horizon, and a monumental achievement for science. But like all scientists, opening the door to a new “first” only increases our drive to surpass what we’ve accomplished and improve our capabilities beyond anything we’ve achieved before. For an event horizon, that means higher resolutions and sharper images, and we have two scientific ways to get there: probing higher frequencies and extending the length of our baseline to beyond the limits of planet Earth.

Both of these are technologically possible, and will likely, over the coming years and decades, be how we push past our scientific limits. Come learn how.

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!

10 Deep Lessons From Our First Image Of A Blac…

10 Deep Lessons From Our First Image Of A Black Hole’s Event Horizon

6. Black holes are dynamic entities, and the radiation emitted from them changes over time. With a reconstructed mass of 6.5 billion solar masses, it takes roughly a day for light to travel across the black hole’s event horizon. This roughly sets the timescale over which we expect to see features change and fluctuate in the radiation observed by the Event Horizon Telescope.

Even with observations that span only a few days, we’ve confirmed that the structure of the emitted radiation changes over time, as predicted. The 2017 data contains four nights of observations. Even glancing at these four images, you can visually see how the first two dates have similar features, and the latter two dates have similar features, but there are definitive changes that are visible — and variable — between the early and late image sets. In other words, the features of the radiation from around M87’s black hole really are changing over time.”

I’ve heard some grumbling over the past day that people are unimpressed with the Event Horizon Telescope collaboration’s big reveal. Maybe the image doesn’t look pretty enough for some people; maybe it doesn’t have the sharpness or level of detail that people are used to from observatories like Hubble.

Well, may I please introduce you to science? If you knew what we’ve actually learned by taking this image, you might change your tune. Read this, and see if you’re not impressed now!

10 Deep Lessons From Our First Image Of A Blac…

10 Deep Lessons From Our First Image Of A Black Hole’s Event Horizon

6. Black holes are dynamic entities, and the radiation emitted from them changes over time. With a reconstructed mass of 6.5 billion solar masses, it takes roughly a day for light to travel across the black hole’s event horizon. This roughly sets the timescale over which we expect to see features change and fluctuate in the radiation observed by the Event Horizon Telescope.

Even with observations that span only a few days, we’ve confirmed that the structure of the emitted radiation changes over time, as predicted. The 2017 data contains four nights of observations. Even glancing at these four images, you can visually see how the first two dates have similar features, and the latter two dates have similar features, but there are definitive changes that are visible — and variable — between the early and late image sets. In other words, the features of the radiation from around M87’s black hole really are changing over time.”

I’ve heard some grumbling over the past day that people are unimpressed with the Event Horizon Telescope collaboration’s big reveal. Maybe the image doesn’t look pretty enough for some people; maybe it doesn’t have the sharpness or level of detail that people are used to from observatories like Hubble.

Well, may I please introduce you to science? If you knew what we’ve actually learned by taking this image, you might change your tune. Read this, and see if you’re not impressed now!

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!

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!

This Is What We Know About Black Holes In Adva…

This Is What We Know About Black Holes In Advance Of The Event Horizon Telescope’s First Image

“For hundreds of years, humanity has expected black holes to exist. Over the course of all of our lifetimes, we’ve collected an entire suite of evidence that points not only to their existence, but to a fantastic agreement between their expected theoretical properties and what we’ve observed. But perhaps the most important prediction of all — that of the event horizon’s existence and properties — has never been directly tested before.

With simultaneous observations in hand from hundreds of telescopes across the globe, scientists have finished reconstructing an image, based on real data, of the largest black hole as seen from Earth: the 4 million solar mass monster at the center of the Milky Way. What we’ll see on April 10 will either further confirm General Relativity or cause us to rethink all that we believe about gravity. Eager with anticipation, the world now awaits.”

The Event Horizon Telescope will, on April 10 (tomorrow, at the time of this writing), release an image two years in the making: of the event horizon of the black hole at the Milky Way’s center. Many will look at this as the first definitive proof that black holes truly exist, but we mustn’t forget all the (overwhelming!) evidence we already have in hand. There is a ton that we already know about black holes that has been demonstrated observationally, and all of it is in spectacular agreement with what we theoretically expect.

On the eve of the Event Horizon Telescope’s big announcement, take some time to get a little perspective, and learn what we already know about black holes!