Pictured at the top of this image (linked to below, for whomever actually decides which lists get published) is IC 297, a spiral galaxy located about about 650 million light-years from Earth in the constellation of Leo Minor.
Located just under the galaxy (separated by thousands of light-years in reality) is Hanny’s Voorwerp — one of the strangest structures in existence. (and that says a lot, given how many mind-bogglingly strange some of the things Hubble [and several other groundbreaking telescopes] has unveiled are). Besides being strange, the structure is also very massive.. coming in at a diameter that exceeds that of the Milky Way. (More than 100,000 light-years)
The most likely origin of the structure is a no-longer active quasar once located in IC 297’s central core. Sometime, in the distant past, the quasar spat out all of the ghastly green material that twisted into filaments comprising this unique structure.