The image highlights the galaxy's structure: a subtle, reddish bulge surrounding a bright nucleus, a blue disk of stars running parallel to the dust lane, and a transparent outer halo.

While the planetary nebula phase is thought to last for around 10, 000 years, astronomers estimate the age of the outer filamentary portions of this halo to be 50, 000 to 90, 000 years.

As a result, they argue, there could be hundreds of these black holes in the outer reaches of the Milky Way halo.