Hanny’s Voorwerp, which is Dutch for Hanny’s Object, was discovered in 2007 by a school teacher who was participating in the Galaxy Zoo project, where volunteers classify galaxies by their certain characteristics. It is a rare type of astronomical object known as a ‘quasar ionization echo’.
Located roughly 650 million light years away, the object is close by to the spiral galaxy IC 2497 and is about the size of a small galaxy.
The bright, glowing cloud of gas is visible because of a beam of light from a nearby quasar – a bright, energetic object powered by a black hole – illuminated it. This quasar could now be long gone, having stopped beaming light some 200,000 years ago.
The apparent hole in the centre of Hanny’s Voorwerp may actually be a shadow caused by an object close to the quasar that blocked some of the light as it traveled towards the gas.