Research Team Discovers Path to Razor-Sharp Black Hole Images

by | Mar 23, 2020 | Galaxies, Supermassive Black Holes | 0 comments

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.

Hello and Welcome to Monday. And I am here to tell you this Monday is lit. 

Well, maybe not really, but our first story describes how we can understand the light disc around black holes in a new and truly spectacular way.

Last year the Event Horizon Telescope people shared the highest resolution image ever acquired of the region surrounding a black hole. This fuzzy orange donut shows us how light and hot light-emitting material swarms the Super-massive Black Hole in the core of the galaxy M87. Over the past year, a lot of folks have asked us to try and explain the asymmetric orange blob, and we’ve done our best, but it turns out that if an image causes 100 questions, a video may answer a 1000. 

A team led by Michael Johnson of the Harvard Center for Astrophysics has modeled how light shining toward a black hole, but with bad aim that causes it to miss the black hole, can get bent to trace out rings and arcs of light. Their video, which you can see in the show notes on our site, DailySpace.org, looks out how closer-in paths lead to sharper lines, as trapped light follows close-in orbits, while a fuzzy outer glow comes for the lazier paths of less on-target light. These paths are called photon rings. Since light that passes close to the star has less distance to cover, this light may swing wide around the black hole numerous times before traveling to the observer, creating the bright rings seen in this simulation. Light further out, with larger orbits that take longer to travel, will have been retraced fewer times, creating fainter and fuzzier appearing rings. 

While these fine structures can’t be seen in the fuzzy donut from the Event Horizon Telescope, there is the possibility of obtaining images that can see them with near future technology. In the article on this research published in Science Advances, the team describes how two radio telescopes, spread between our planet’s surface and orbit, would have sufficient resolution to map out these delicate structures and reveal the nature of a black hole. It turns out simple factors like how fast a black hole is spinning can have major relativistic effects on how light near the black hole travels, and some day, we may be able to image the stack rings of light around a black hole to study otherwise unmeasurable characteristics of these light-eating dense objects. Black holes cast a shadow on the image of bright surrounding material because their strong gravitational field can bend and trap light. The shadow is bounded by a bright ring of light, corresponding to photons that pass near the black hole before escaping. The ring is actually a stack of increasingly sharp subrings, and the n-th subring corresponds to photons that orbited the black hole n/2 times before reaching the observer. This animation shows how a black hole image is formed from these subrings and the trajectories of photons that create the image. CREDIT: Center for Astrophysics | Harvard & Smithsonian

We can’t stress this enough – Black holes themselves do not shine light. The blackness we see in the Event Horizon Image is the shadow in space where a black hole says to the light that gets too close “Thou shall not pass” and then traps that light forever within its Schwartzschild radius. 

While Black Holes don’t emit light, the material that is falling toward them can become extraordinarily dense, light up with its own nuclear reactions, and radiate massive quantities of light. This material, called an accretion disk, is responsible for the bright light coming from quasars and other kinds of active galaxies. It is also responsible for a whole lot of misleading headlines, including the headline for our next story, “Blistering radiation from active black hole snowplows immense amounts of mechanical energy through space.” To be clear – radiation … which is a fancy word for light… is responsible for any energy redistribution discussed in the next few minutes. 

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