An inversion nebula is a type of nebula composed of unstable plasma strands. Although theorized by Federation scientists, inversion nebulae have never been observed in the Alpha Quadrant. They are believed to burn out in only a few years. In 2373, the USS Voyager discovered an inversion nebula in the Delta Quadrant that was centuries old. They found that an unusual dampening field was responsible for isolating each plasma strand as it ignited, averting a catastrophic chain reaction. The dampening field was generated from a hidden space station occupied by Marayna, whose function was to preserve the nebula so that its beauty could be enjoyed by her people.

Marayna surreptitiously tapped into Voyager's systems and interacted with the crew via a holographic character, during which she became fond of Tuvok. In an effort to compel him to stay with her, she used the nebula as a weapon, igniting specific plasma strands to damage Voyager. Tuvok eventually convinced her that she should pass on her duty to another and return to the company of her kind. (VOY: "Alter Ego")

While there are no phenomena in astrophysics called inversion nebulae, there are nebulae that do contain unstable plasma. Planetary nebulae consist of a glowing shell of gas and plasma that has been ejected from low to medium mass stars at the end of their lives. Because most of the gas in a typical planetary nebula is ionised (i.e. a plasma), the effects of magnetic fields can be significant, giving rise to phenomena such as filamentation and plasma instabilities (as with the so-called inversion nebulae in Star Trek).

At the end of the star's life, during the red giant phase, the outer layers of the star are expelled via pulsations and strong stellar winds. Without these opaque layers, the remaining core of the star shines brightly and is very hot. The ultraviolet radiation emitted by this core ionises the ejected outer layers of the star which radiate as a planetary nebula. The name originates from a supposed similarity in appearance to giant planets. About 1,500 planetary nebulae are known to exist in our galaxy, out of around 200 billion stars. These include the famous NGC 6853, The Dumbbell Nebula and NGC 6543, The Cat's Eye Nebula. They are a relatively short-lived phenomenon, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years. This short lifetime compared to stellar lifetimes accounts for their rarity. They are found mostly near the plane of the Milky Way, with the greatest concentration in the galactic Bulge. A typical planetary nebula is roughly 3 parsecs across.