A team of astronomers, led by Peter Maksym of the Center for Astrophysics | Harvard & Smithsonian (CfA), in Cambridge, Massachusetts, has traced the rays back to the galaxy’s core, the location of an active supermassive black hole. Although the researchers have developed several plausible theories for the lightshow, 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 proposed 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 sunset. However, the rays in IC 5063 are happening on a vastly larger scale, shooting across at least 36,000 light-years.
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.