NGC 5189, Planetary Nebula in Musca

Distance: 1800 Light Years


Planetary nebulae (PN's) are formed in the final stage of the lifetime of stars which begin their lives having a total mass of one to eight solar masses (suns). NGC 5189 represents the gaseous remains of a sunlike star which has entered its final stages of evolution. The intense radiation from the stellar remnant ionizes the stars previously ejected gases. The inner shell structures glow predominantly green-blue from ionized oxygen (OII and OIII) and nitrogen while hydrogen in the outer shell emits in the red wavelengths. The planetary nebula stage of an intermediate mass star lasts only 10 to 30 thousand years, an astronomical instant in the overall life of a star. Eventually the ejected envelope disperses into the interstellar medium enriching it with both light and heavier elements originally created deep within the nuclear furnace of the now dead star.


NGC 5189 was first noted by James Dunlop in 1826 and again by John Herschel a decade later. Herschel was sufficiently intrigued by what he saw to describe it as “a very strange object,” and published a drawing that clearly shows its distinctive S-shape. NGC 5189 is located some 1800 light-years away in the constellation of Musca (The Fly). NGC 5189 is also sometimes nicknamed the Spiral Planetary Nebula, after the only sign of symmetry in its apparently chaotic structure. It has formed from the expanding remains of the dying star HD 117622 which is colliding with previously ejected gas and dust. Although it appears disordered, careful examination of the spectra of individual knots and condensations reveals an underlying symmetry, which is a hallmark of a planetary nebula.