A Glowing Ghost in Deep Space

Hanny's Voorwerp is a mysterious glowing blob that acts as a light echo from a long-dead quasar. Discovered by a schoolteacher, it serves as a cosmic time machine revealing the past intensity of a nearby galaxy.

The object was found by volunteer Hanny van Arkel while she was sorting galaxy images online. It shines because a massive black hole in the neighboring galaxy IC 2497 emitted intense radiation that hit a cloud of gas. Because that light takes so long to travel, we are essentially seeing a flash of light from a giant explosion that happened thousands of years ago. It remains one of the most famous success stories of crowdsourced citizen science.