Black holes are understood to be some of the Universe’s most extreme and rapacious entities, greedily guzzling everything in their vicinity. Their gravity is so powerful, nothing – even light – can escape their grasp, making them difficult to observe. However, astronomers now suspect they may have detected a black hole’s dust ring from the shadows it has cast.
A “tantalising” narrow bright rays and dark shadows beaming from nearby galaxy IC 5063 have been imaged by NASA’s Hubble Space Telescope.
Although several plausible theories for the intriguing light-show are under consideration, the most exciting theory suggests an inner-tube-shaped ring of dusty material, known as the torus, surrounding the black hole is casting its shadow into space.
Professor Peter Maksym, of the Harvard-Smithsonian Center for Astrophysics, who has led the study, thinks the dust disk around the black hole does not block all of the light.
Instead, gaps in the disk allow some light to creep in, creating brilliant cone-shaped rays on a vast scale, stretching at least 36,000 light-years.
Some of the light hits dense patches in the ring, casting this finger-shaped shadow into the cosmos.
These beams and shadows are only visible outside the galaxy because the black hole and its ring are positioned sideways relative to the galaxy’s plane.
Professor Maksym suggests the interplay of light and shadow offers a unique insight into the distribution of material encircling the black hole.
He believes Hubble’s latest observations could offer an indirect probe of the disk’s mottled structure.
He said: ”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 hypothesised.
“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 behaviour of supermassive black holes and their environments.
“As a galaxy evolves, it is shaped by its central black hole.”
If the astronomer’s “shadow” theory is accurate, the rays provide evidence IC 5063’s disk is extremely thin, which goes some way to explaining why light is leaking around the structure.
Additional observations of similar black holes made by NASA’s Chandra X-ray Observatory also detected X-rays leaking from the torus, giving a mottled “Swiss cheese” appearance, the space agency said.
Professor Maksym thinks these holes may be created by the disk being torqued by internal forces, causing it to warp.
He 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.”
The astronomer added he intends to pursue his study of the galaxy to determine whether his theory is correct.
He said: ”We will want to keep investigating, and it will be great if other scientists try to test our conclusions, too, with new observations and modelling.
“This is a project that is just begging for new data because it raises more questions than it answers.”