Planetary nebulae

Definition

A planetary nebula is an expanding shell of ionized gas ejected from red giant stars late in their life cycles. These nebulae glow due to the ultraviolet radiation from the hot central star remnant.

5 Must Know Facts For Your Next Test

1. The term 'planetary nebula' is a misnomer; it has no relation to planets but was named so because of its planet-like appearance through early telescopes.
2. Planetary nebulae are crucial for enriching the interstellar medium with heavier elements like carbon and nitrogen.
3. Most planetary nebulae have a lifespan of about 10,000 to 20,000 years before dispersing into space.
4. The central star left behind after a planetary nebula phase eventually becomes a white dwarf.
5. Planetary nebulae exhibit various shapes, including spherical, elliptical, and bipolar forms.

Review Questions

• What primarily causes the glow of a planetary nebula?
• How long does the planetary nebula phase typically last?
• What happens to the central star of a planetary nebula once it has dispersed?

Related terms

Red Giant:

A late stage in stellar evolution where the star expands significantly after exhausting hydrogen in its core.

White Dwarf:

The dense stellar remnant left behind after a low- to intermediate-mass star expels its outer layers and ceases nuclear fusion.

Ionization:

The process by which an atom or molecule acquires a positive or negative charge by gaining or losing electrons, often induced by high-energy photons.