APOD: Planetary Nebula Mz3: The Ant Nebula (2021 Apr 25)

[Fission]

Yes, the Red Giant is an end of star event. That is the problem. The commentary states this planetary nebula happened to a star similar to the Sun. That is, a mid life star. If so, this planetary nebula is not consistent with the past definition of a planetary nebula which is an end of stellar event.

[Chris Peterson]

Yes, the Red Giant is an end of star event. That is the problem. The commentary states this planetary nebula happened to a star similar to the Sun. That is, a mid life star. If so, this planetary nebula is not consistent with the past definition of a planetary nebula which is an end of stellar event.

You are misreading it. A red giant is a star like the Sun, simply at a different stage of evolution. Likewise for the white dwarf that is now the source of ionizing radiation in this nebula.

[johnnydeep]

Yes, the Red Giant is an end of star event. That is the problem. The commentary states this planetary nebula happened to a star similar to the Sun. That is, a mid life star. If so, this planetary nebula is not consistent with the past definition of a planetary nebula which is an end of stellar event.

You are misreading it. A red giant is a star like the Sun, simply at a different stage of evolution. Likewise for the white dwarf that is now the source of ionizing radiation in this nebula.

Just to add some clarifying details that I wasn't appreciating, the Sun (and other stars like it such as the pair at the center of Mz3) will, in the far future, first become a red giant and then a white dwarf! From https://en.wikipedia.org/wiki/Sun#After ... exhaustion

After core hydrogen exhaustion
The Sun does not have enough mass to explode as a supernova. Instead, when it runs out of hydrogen in the core in approximately 5 billion years, core hydrogen fusion will stop and there will be nothing to prevent the core from contracting. The release of gravitational potential energy causes the luminosity of the star to increase, ending the main sequence phase and leading the star to expand over the next billion years: first into a subgiant, and then into a red giant.[127][129][130] The heating due to gravitational contraction will also lead to hydrogen fusion in a shell just outside the core, where unfused hydrogen remains, contributing to the increased luminosity, which will eventually reach more than 1000 times its present luminosity.[127] As a red giant, the Sun will grow so large that it will engulf Mercury, Venus, and probably Earth.[130][131] The Sun will spend around a billion years as a red-giant branch star and lose around a third of its mass.[130]
...
The post-asymptotic-giant-branch evolution is even faster. The luminosity stays approximately constant as the temperature increases, with the ejected half of the Sun's mass becoming ionized into a planetary nebula as the exposed core reaches 30,000 K. The final naked core, a white dwarf, will have a temperature of over 100,000 K, and contain an estimated 54.05% of the Sun's present-day mass.[130] The planetary nebula will disperse in about 10,000 years, but the white dwarf will survive for trillions of years before fading to a hypothetical black dwarf.[134][135]