A mysterious alignment of stellar "ghosts" from dead stars haunts the heart of the Milky Way, and scientists may finally know why.
These cosmic specters exist in the form of planetary nebulas, clouds of gas that are expelled by dying stars at the end of their lives. These can resemble butterflies or hourglasses with the smoldering remains of the star at their heart. The sun, when it runs out of fuel for nuclear fusion at its core and after it has swelled out as a red giant and swallowed the inner planets in around 5 billion years, will leave similar gaseous remains around a white dwarf star.
