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 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 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 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 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!
6 Supermassive Questions On The Eve Of The Event Horizon Telescope’s Big Announcement
“3.) Is a black hole’s event horizon circular, as predicted, or does it take on a different shape? Although all physically realistic black holes are expected to spin to some degree, the event horizon’s shape is predicted to be indistinguishable from that of a perfect sphere.
But other shapes are possible. Some objects bulge along their equators when they rotate, creating a shape known as an oblate spheriod, such as planet Earth. Others creep up along their rotational axes, resulting in a football-like shape known as a prolate spheroid. If General Relativity is correct, a sphere is what we anticipate, but there’s no substitute for making the critical observations ourselves. When the images come out on April 10, we should have our answers.”
On April 10, one of the longest-awaited advances will finally be upon us, as the Event Horizon Telescope collaboration will reveal their very first image of a black hole’s event horizon. It should test General Relativity as never before, including measuring the black hole’s event horizon, its sphericity, the radiation coming from around it, and many other properties.
What’s the full suite of what our first direct image of a black hole might teach us? Come get the amazing science behind a spectacular discovery we’ve all been waiting for!
2019’s Science Breakthrough Of The Year Will Show Us A Black Hole’s Event Horizon
“Although the Event Horizon Telescope team has detected structure around the black hole at our galaxy’s center, we still don’t have a direct image. This requires understanding our atmosphere and the changes occurring within it, combining the data, and writing novel algorithms to co-process them. It’s a work in progress, but the first half of 2019 is when the final, first images ought to arrive. Some of us were hoping for the images this year or even last year, but it’s most important that we take the time and the care to get it right.
When these images finally do arrive, there will no longer be any doubt as to whether black holes exist, and whether they exist with the properties that Einstein’s greatest theory predicts. 2019 will be the year of the event horizon, and for the first time in all of history, we’ll finally know, conclusively, what they look like.”
All over the world, people are recapping their “best of 2018″ stories, but why limit ourselves to the past? We know, in many cases, what data we’ve collected, what analysis is being done to it, and what we anticipate learning about the Universe from it. Well, one of the big discoveries that’s on the way is the first direct image (possibly two images) of the event horizon of a black hole.
Will what we see agree with Einstein? What direction/orientation will the accretion disk display? Will there be hot spots in the surrounding matter, as expected? And will it have the right size to line up with our other measurements of the black hole’s mass?
Regardless of the outcome, 2019 should be the year of the black hole event horizon! Come find out the incredible science of how.
This Is How We Will Successfully Image A Black Hole’s Event Horizon
“Normally, the resolution of your telescope is determined by two factors: the diameter of your telescope and the wavelength of light you’re using to view it. The number of wavelengths of light that fit across your dish determines the optimal angular diameter you can resolve. Yet if this were truly our limits, we’d never see a black hole at all. You’d need a telescope the diameter of the Earth to view even the closest ones in the radio, where black holes emit the strongest and most reliably.
But the trick of very-long baseline interferometry is to view extremely bright sources, simultaneously, from identical telescopes separated by large distances. While they only have the light-gathering power of the surface area of the individual dishes, they can, if a source is bright enough, resolve objects with the resolution of the entire baseline. For the Event Horizon Telescope, that baseline is the diameter of the Earth.”
The Event Horizon Telescope is one of the best examples of international collaboration, and its necessity, in answering questions that are too big for any one nation to do alone. Part of the reason for that is geography: if you want to get the highest-resolution information possible about the Universe, you need the longest-baseline of simultaneous observations that it’s possible to make. That means, if you want to go as hi-res as possible, using the full diameter of the Earth. From the Americas to Eurasia to Africa, Australia and even Antarctica, radio astronomers are all working together to create the first image of a black hole’s event horizon.
What does it look like? Is General Relativity correct? As soon as the Event Horizon Telescope team releases their first images, we’ll know. Come watch a live-blog of a talk from their team today, and get the answers as soon as we know them!
This Is Why The Event Horizon Telescope Still Doesn’t Have An Image Of A Black Hole
“Of all the black holes visible from Earth, the largest is at the galactic center: 37 μas.
With a theoretical resolution of 15 μas, the EHT should resolve it.
Despite the incredible news that they’ve detected the black hole’s structure at the galactic center, however, there’s still no direct image.”
Last year, data from the South Pole Telescope, a 10-meter radio telescope located at the South Pole, was added to the Event Horizon Telescope team’s overall set of information. Here we are, though, half a year later, and we still don’t have a direct image of the event horizon for the galactic center’s black hole. There aren’t any problems; the issue is that we have to successfully calibrate and error-correct the data, and that takes time and care to get it right. Science isn’t about getting the answer in the time you have to get it; it’s about getting the right answer in the time it takes to get things right. From that point of view, there’s every reason this is worth waiting for.
The Event Horizon Telescope team is on the right track; here’s where we are right now in our quest to create the first image of a black hole’s event horizon!
2018 Will Be The Year Humanity Directly ‘Sees’ Our First Black Hole
“No longer will we need to rely on simulations or artist’s conceptions; we’ll have our very first actual, data-based picture to work with. If it’s successful, it paves the way for even longer baseline studies; with an array of radio telescopes in space, we could extend our reach from a single black hole to many hundreds of them. If 2016 was the year of the gravitational wave and 2017 was the year of the neutron star merger, then 2018 is set up to be the year of the event horizon. For any fan of astrophysics, black holes, and General Relativity, we’re living in the golden age.”
Black holes have been dreamed up by theorists for centuries. Even in the aftermath of Newtonian gravity, a spectacular realization came about that if you gathered enough mass together into a small enough volume, the gravitational effects would be so pronounced that nothing, not even light, could escape. These black holes show up with very specific properties in General Relativity, and today in modern astrophysics, we know of three independent ways to make them. But despite observing their effects in many different wavelengths of light, such as the radio and X-ray, we’ve never imaged an event horizon directly. Although a telescope the size of Earth would be able to, that technology is out of reach. Owing to collaboration and human ingenuity, however, we’ve developed an array known as the Event Horizon Telescope that should reveal its first image next year!
Will we see the event horizon of a black hole for the first time? My bet is on yes. Come get the science as to why!