M87* and Sgr A* side-by-side in polarised light

Seen here in polarised light, this side-by-side image of the supermassive black holes M87* and Sagittarius A* indicates to scientists that these beasts have similar magnetic field structures. This is significant because it suggests that the physical processes that govern how a black hole feeds and launches a jet may be universal features amongst supermassive black holes.

The scale shows the apparent size on the sky of these images, in units of micro-arcseconds. A finger held at arm's length measures 1 degree on the sky; a micro-arcsecond is 3.6 billion times smaller than that. In context, the images of these black holes have an apparent size similar to that of a donut on the surface of the Moon.