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Photographing a black hole?

As teased earlier this month, today the Event Horizon Telescope (EHT) project announced and presented the first ever photographs of a black hole — “the last photon orbit.” Another epic story of big science and an international team. The interplay of models and simulations, data capture, and complex processing. And funding.

Much news coverage. Here’s an article by Space.com: “Eureka! Black Hole Photographed for 1st Time.” I’ll add other articles later.

“We have seen what we thought was unseeable,” Sheperd Doeleman, of Harvard University and the Harvard-Smithsonian Center for Astrophysics, said today (April 10) during a press conference at the National Press Club in Washington, D.C.

Doeleman directs the Event Horizon Telescope (EHT) project, which captured the epic imagery. These four photos, which were unveiled today at press events around the world and in a series of published papers, outline the contours of the monster black hole lurking at the heart of the elliptical galaxy M87.

And in case you’re wondering about Sagittarius A*: The EHT team hopes to get imagery of that supermassive black hole soon, Doeleman said today. The researchers looked at M87 first, and it’s a bit easier to resolve than Sagittarius A* because it’s less variable over short timescales, he explained.

In addition, the shape of an event horizon can reveal whether a black hole is spinning, said Fiona Harrison of the California Institute of Technology, the principal investigator of NASA’s black-hole-studying Nuclear Spectroscopic Telescope Array (NuSTAR) mission.

The National Science Foundation (NSF) news has detailed coverage, including papers about the announcement which were published in a special issue of The Astrophysical Journal Letters. See their video “BRIEF, SELF-CONTAINED, NARRATED OVERVIEW of Event Horizon Telescope project and the first black hole.

Space photo
Black hole silhouette. Credit: Event Horizon Telescope collaboration et al.

Here’s the NSF YouTube video of the press event:

Actual press conference starts after ~38 minutes in video.

Other YouTube videos

Perimeter Institute for Theoretical Physics (published on Apr 10, 2019)

The EHT Collaboration consists of 13 stakeholder institutes; the Academia Sinica Institute of Astronomy and Astrophysics, the University of Arizona, the University of Chicago, the East Asian Observatory, Goethe-Universitaet Frankfurt, Institut de Radioastronomie Millimétrique, Large Millimeter Telescope, Max Planck Institute for Radio Astronomy, MIT Haystack Observatory, National Astronomical Observatory of Japan, Perimeter Institute for Theoretical Physics, Radboud University and the Smithsonian Astrophysical Observatory.

Time – Scientists from The NSF Hold Conference on Results from The Event Horizon Telescope.

Scientists from the National Science Foundation hold a news conference on the groundbreaking results from the Event Horizon Telescope, releasing the first image of a black hole – a dense mass that distorts space and time, with gravity so strong not even light can escape.

Veritasium (published on Apr 10, 2019) – which explains the 40 microarcsecond (μas) image, with links to additional information in the description.

The Event Horizon Telescope Collaboration observed the supermassive black holes at the center of M87 and our Milky Way galaxy (SgrA*) finding the dark central shadow in accordance with General Relativity, further demonstrating the power of this 100 year-old theory.

TEDx Talks (published Dec 7, 2016) via Phys.org Scientist superstar Katie Bouman designed algorithm for black hole image

To take a photo of a black hole, you’d need a telescope the size of a planet. That’s not really feasible, but Katie Bouman and her team came up with an alternative solution involving complex algorithms and global cooperation. Katie Bouman is a Ph.D. candidate in the Computer Science and Artificial Intelligence Laboratory (CSAIL) at the Massachusetts Institute of Technology (MIT), under the supervision of William T. Freeman. She previously received a B.S.E. in Electrical Engineering from the University of Michigan, Ann Arbor, MI in 2011 and an S.M. degree in Electrical Engineering and Computer Science from MIT, Cambridge, MA in 2013. The focus of Katie’s research is on using emerging computational methods to push the boundaries of interdisciplinary imaging. This talk was given at a TEDx event using the TED conference format but independently organized by a local community.

“I’m so excited that we finally get to share what we have been working on for the past year!” the 29 year-old Bouman, a postdoctoral researcher at the Harvard-Smithsonian Center for Astrophysics

In 2016, Bouman developed an algorithm named CHIRP to sift through a true mountain of data gathered by the Event Horizon Telescope project from telescopes around the world to create an image.

“No one algorithm or person made this image,” wrote Bouman, who in the fall will begin work as an assistant professor at the California Institute of Technology (Cal Tech).

“It required the amazing talent of a team of scientists from around the globe and years of hard work to develop the instrument, data processing, imaging methods, and analysis techniques that were necessary to pull off this seemingly impossible feat,” she said on Facebook.

Other articles

Space.com: “All Your Questions About the New Black Hole Image Answered

Example: Why is the image blurry?

With current technology, that’s the highest resolution achievable. The resolution of the Event Horizon Telescope is about 20 microarcseconds. (One microarcsecond is about the size of a period at the end of a sentence if you were looking at it from Earth and that period was in a leaflet left on the moon, according to the Journal of the Amateur Astronomers Association of New York.)

If you take an ordinary photo that contains millions of pixels, blow it up a few thousand times and smooth it out, you’ll see about the same resolution as seen in the black hole image, according to Geoffrey Crew, the vice chair of the Event Horizon Telescope.

Documentaries

Smithsonian Channel via Space.com: ” ‘Black Hole Hunters’ Shows Epic Chase to Capture First Images

The one-hour documentary, called “Black Hole Hunters,” debuts today (April 12) at 9 p.m. EDT and at 9 p.m. PDT, depending on your time zone. It follows Harvard University astronomer Shep Doeleman and his team, which this week released the first images of a black hole, created using a networked set of telescopes called the Event Horizon Telescope (EHT).

Screenshot
EHT Locations
Screenshot
Location Correlation
Screenshot
An Image Processing Algorithm Team

Notes

Wiki: Photon sphere

photon sphere is a spherical area or region of space where gravity is strong enough that photons are forced to travel in orbits. The radius of the photon sphere—which is also the lower bound for any stable orbit—is, for a Schwarzschild black hole …

Wiki: Very-long-baseline interferometry

Very-long-baseline interferometry (VLBI) is a type of astronomical interferometryused in radio astronomy. In VLBI a signal from an astronomical radio source, such as a quasar, is collected at multiple radio telescopes on Earth. The distance between the radio telescopes is then calculated using the time difference between the arrivals of the radio signal at different telescopes. This allows observations of an object that are made simultaneously by many radio telescopes to be combined, emulating a telescope with a size equal to the maximum separation between the telescopes.

Wiki: Multi-messenger astronomy

Multi-messenger astronomy is astronomy based on the coordinated observation and interpretation of disparate “messenger” signals. Interplanetary probes can visit objects within the Solar System, but beyond that, information must rely on “extrasolar messengers”. The four extrasolar messengers are electromagnetic radiationgravitational wavesneutrinos, and cosmic rays. They are created by different astrophysical processes, and thus reveal different information about their sources.

2 thoughts on “Photographing a black hole?

  1. As noted in some of the articles about the photos of the massive black hole at the center of M87, these “photographs” are not like the snapshots we take with our smartphones in several ways. They are not “taken” using visible light. And the processing of radio wave data to generate pixels for the images is exceedingly complex (although smartphone photo processing, especially for low light conditions, has become more and more intensive, even permitting adjusting focus and background blur in post-processing).

    It’s been somewhat of a visceral breakthrough for me using infrared cameras on a daily basis: that all light — all EM radiation, not just the visible portion of the spectrum, behaves according to the same rules, e.g., regarding refraction, reflection, shadowing, etc.

  2. Another example of an article on this event, from Vox.com by Brian Resnick: “How to make sense of the black hole image, according to 2 astrophysicists — Think on this: The light at the center of the black hole picture has been forever removed from the observable universe.”

    Some may not be impressed by the slight blurriness of the image. But there’s so much more to it than what immediately meets the eye. Two astrophysicists — Sheperd Doeleman, the project leader of the Event Horizon Telescope, and Katie Mack of North Carolina State University, who was not involved with the effort — walked me through a few of the coolest aspects of the image that helped me appreciate just wonderfully mind-blowing it is.

    You might think this ring of material, or the innermost edge of it, represents that event horizon. It actually doesn’t. … That boundary is known as the photon orbit, and its diameter is about 2.5 times larger than that of the event horizon.

    The light you do see in this image (which are really representations of radio waves, …) isn’t just coming from the sides of the black hole, it’s coming from behind it, from in front of it, from all directions. Space and time is so warped, that some of the light orbits the black hole in a circle.

    The telescopes used in the Event Horizon effort were radio telescopes. That means they only “see” radio frequencies on the electromagnetic spectrum.

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