New telescopes could help spot ‘photon ring’ of the first black hole ever imaged
Faint rings of light surrounding enormous black holes could be spotted with the help of a future generation of telescopes in space. The doughnut-shaped glow spotted in the first image of a black hole, released in April 2019 by the Event Horizon Telescope collaboration (SN: 4/10/19), is more complex than the worldwide network of radio telescopes could discern. The black hole’s gravity is so intense that some particles of light, called photons, can circle the black hole partway — or once, twice or multiple times — before escaping to be picked up by telescopes. Those orbiting photons produce a “photon ring,” made up of a series of subrings — circles of light that appear successively thinner and harder for telescopes to pick out. “It’s sort of like a hall of mirrors, where we’re getting an infinite series of images,” says astrophysicist Michael Johnson of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. Now, Johnson and colleagues calculate that, with the help of new telescopes in...