Magnetic fields of order 101–102 Gauss that are present in the envelopes of red giant stars are ejected in common envelope scenarios.

These fields could be responsible for the launching of magnetically driven winds in protoplanetary nebulae. Using 2D simulations of magnetized winds interacting with an envelope drawn from a 3D simulation of the common envelope phase, we study the confinement, heating, and magnetic field development of post-common envelope winds.

We find that the ejected magnetic field can be enhanced via compression by factors up to ~104 in circumbinary disks during the self-regulated phases.

We find values for the kinetic energy of the order of 1046 erg that explain the large values inferred in protoplanetary nebula outflows.

We show that the interaction of the formed circumbinary disk with a spherical, stellar wind produces a “tapered” flow that is almost indistinguishable from an imposed tapered flow.

This increases the uncertainty of the origin of protoplanetary nebula winds, which could be either stellar, circumstellar (stellar accretion disk), circumbinary (circumbinary accretion disk), or a combination of all three.

Within this framework, a scenario for self-collimation of weakly magnetized winds is discussed, which can explain the two objects where the collimation process is observationally resolved, HD 101584 and Hen 3-1475.

An explanation for the equatorial, molecular hydrogen emission in CRL 2688 is also presented.

A planetary nebula, abbreviated as PN or plural PNe, is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives.

The term “planetary nebula” is a misnomer because they are unrelated to planets or exoplanets. The term originates from the planet-like round shape of these nebulae observed by astronomers through early telescopes.

The first usage may have occurred during the 1780s with the English astronomer William Herschel who described these nebulae as resembling planets; however, as early as January 1779, the French astronomer Antoine Darquier de Pellepoix described in his observations of the Ring Nebula, “very dim but perfectly outlined; it is as large as Jupiter and resembles a fading planet”. Though the modern interpretation is different, the old term is still used.

All planetary nebulae form at the end of the life of a star of intermediate mass, about 1-8 solar masses.

It is expected that the Sun will form a planetary nebula at the end of its life cycle.

They are a relatively short-lived phenomenon, lasting perhaps a few tens of thousands of years, compared to considerably longer phases of stellar evolution.

Once all of the red giant’s atmosphere has been dissipated, energetic ultraviolet radiation from the exposed hot luminous core, called a planetary nebula nucleus (PNN), ionizes the ejected material.Absorbed ultraviolet light then energizes the shell of nebulous gas around the central star, causing it to appear as a brightly coloured planetary nebula.

Planetary nebulae likely play a crucial role in the chemical evolution of the Milky Way by expelling elements into the interstellar medium from stars where those elements were created. Planetary nebulae are observed in more distant galaxies, yielding useful information about their chemical abundances.

Starting from the 1990s, Hubble Space Telescope images revealed that many planetary nebulae have extremely complex and varied morphologies. About one-fifth are roughly spherical, but the majority are not spherically symmetric.

The mechanisms that produce such a wide variety of shapes and features are not yet well understood, but binary central stars, stellar winds and magnetic fields may play a role.

The study was published in Astrophysical Journal