Three new ghosts just appeared in Cassiopeia — and it took 100 hours of looking to see them

High in the Cassiopeia constellation, near the bright multi-star system gamma Cassiopeia, two faint nebulae known as the Ghosts of Cassiopeia have long glowed red where starlight strikes their hydrogen gas. Now a 100-hour observation with a special oxygen filter has revealed three more apparitions beside them — Objects 1, 2 and 3 — shining blue with ionised oxygen, the oxygen given its charge by something astronomers are still working out. One may be gas piled up like water at a boat's bow as the star system ploughs through space; another could be a planetary nebula, if a white dwarf is found at its heart. The ghosts, for now, keep some of their mystery.