The now iconic image of M87’s monster black hole–an object described as “the most perfect macroscopic objects in the universe, the only elements in their construction are our concepts of space and time”– captured in April 2019 by the Event Horizon team highlighted the eerie orange glow of it’s shadow.
The image, reported the EHT team, marked the culmination of years of work undertaken by a team of 200 scientists in 59 institutes across 18 countries, drawing on data collected by eight telescopes whose locations range from Hawaii to the South Pole, creating the equivalent of a lens the size of planet Earth that’s 4,000 times more powerful than the Hubble Space Telescope.
The Shadow Knows–Movie of the History of the Visible Universe
The image of the behemoth captured light from the entire universe wrapping around the object in a nested series of rings, said astrophysicist Peter Galison at Harvard. “As we peer into these rings, we are looking at light from all over the visible universe, we are seeing farther and farther into the past, a movie, so to speak, of the history of the visible universe.”
“Revealed by a Quirk of Alignment”
Today, the Hubble Space Telescope astronomers announced that “by a quirk of alignment, scientists may be getting a glimpse of the structure of the disk around the black hole in nearby galaxy IC 5063, first brought to the attention of astronomer’s at Harvard’s Center for Astrophysics by a discovery by a lone citizen astronomer, so starkly different from the Earth-sized EHT team of 200 scientists.
The Hubble Space Telescope observed a collection of narrow bright rays and dark shadows beaming out of the blazingly bright center of the active galaxy. created as the object pulls stars and gas into a disk that swirls around them generating a prodigious amount of energy, producing a powerful gusher of light from superheated infalling gas.”
This Hubble image of the heart of IC 5063 shown at the top of the page reveals a mixture of bright rays and dark shadows coming from the blazing core of its supermassive black hole. Astronomers suggest that a ring of dusty material surrounding the black hole may be casting its shadow into space. The Hubble Site reports that “some light penetrates gaps in the dust ring, creating the bright rays that resemble the floodlights accompanying a Hollywood movie premier. These telltale beams offer clues to the distribution of material near the black hole that is causing the shadow play.”
Traced Back to the Galaxy’s Core
A team of astronomers, led by Peter Maksym of the Center for Astrophysics (CfA), has traced the rays back to the galaxy’s core, the location of an active supermassive black hole, where the monster object is frenetically feeding on infalling material, producing a powerful gusher of light from superheated gas. Although the researchers have developed several plausible theories for the lightshow, reports the CfA, “the most intriguing idea suggests that an inner-tube-shaped ring, or torus, of dusty material surrounding the black hole is casting its shadow into space.”
According to Maksym’s scenario, the dust disk around the black hole doesn’t block all of the light. Gaps in the disk allow light to beam out, creating brilliant cone-shaped rays similar to the fingers of light sometimes seen at Earth’s sunset. However, the rays in IC 5063 are happening on a vastly larger scale, shooting across at least 36,000 light-years.
Casting Light Beams Far Outside the Galaxy
Some of the light hits dense patches in the ring, casting the ring’s shadow into space. These shadows appear as dark finger shapes interspersed with bright rays. These beams and shadows are visible because the black hole and its ring are tipped sideways relative to the plane of the galaxy. This alignment allows the light beams to extend far outside the galaxy.
This interplay of light and shadow offers a unique insight into the distribution of material encircling the black hole. In some areas, the material may resemble scattered clouds. If this interpretation is correct, the observations may provide an indirect probe of the disk’s mottled structure.
“I’m most excited by the shadow of the torus idea because it’s a really cool effect that I don’t think we’ve seen before in images, although it has been hypothesized,” Maksym said. “Scientifically, it’s showing us something that is hard—usually impossible—to see directly. We know this phenomenon should happen, but in this case, we can see the effects throughout the galaxy. Knowing more about the geometry of the torus will have implications for anybody trying to understand the behavior of supermassive black holes and their environments. As a galaxy evolves, it is shaped by its central black hole.”
Studying the torus is important because it funnels material toward the black hole. If the “shadow” interpretation is accurate, the dark rays provide indirect evidence that the disk in IC 5063 could be very thin, which explains why light is leaking out all around the structure.
Observations of similar black holes by NASA’s Chandra X-ray Observatory detected X-rays leaking out of holes in the torus, making the structure appear like Swiss cheese. The holes may be caused by the disk being torqued by internal forces, causing it to warp, Maksym said. “It’s possible that the warping creates big enough gaps for some of the light to shine through, and as the torus rotates, beams of light could sweep across the galaxy like lighthouse beams through fog,” he added.
Fascinating Example of Lone Citizen Discovery
In a fascinating example of a discovery by a lone citizen astronomer, Judy Schmidt, an artist and amateur astronomer based in Modesto, California, reports the Harvard CfA, uncovered the dark shadows when she reprocessed Hubble exposures of the galaxy in December 2019. Schmidt routinely culls the Hubble archive for interesting observations that she can turn into beautiful images. She shared those images on her Twitter feed with her many followers, one of whom was Peter Maksym.
“I noticed the dark rays almost immediately after I’d opened the file in Photoshop and began working to enhance them to make sure what I thought I saw was there. I couldn’t see them in the archive thumbnails or the preview of the stretched image in FITS Liberator,” said Schmidt, adding that when she first saw what appeared to be shadows, she thought, “That’s not possible is it?” In her earliest tweets about the phenomena, Schmidt asked her followers, “Are these cones I’m straining to see real?” and “What are they? This is an active galaxy with a supermassive black hole in the middle. Is it casting galaxy-sized shadows? Or are those just star streams?”
It didn’t take long for Maksym and other scientists to notice the tweet and start making conjectures, reports Harvard CfA, which eventually led to the formation of the research team and the discovery.
“Judy has a keen eye for what looks weird, which, as in this case, can have important scientific implications. In December, she noticed some ‘dark rays’ extending from the nucleus of the galaxy IC 5063 and Tweeted to her followers asking if they might be anything interesting,” said Maksym, whose interest was immediately piqued since he was already working on the same galaxy from a different scientific angle. “Several of us chimed in and started speculating what could be causing the rays, and we really had no idea at first. When you read the Twitter thread, you can see how the ideas unfolded in real-time, and transformed into this really unusual research.”
“Older images from telescopes on the ground showed maybe hints of this kind of structure, but the galaxy itself is such a mess that you’d never guess that this is what’s going on without Hubble,” Maksym explained. “Hubble has sharp pictures, is sensitive to faint things, and has a big enough field of view to image the entire galaxy.”