Planetary Nebula M2–9, from the Hubble Space Telescope. Image credit: Bruce Balick (University of Washington), Vincent Icke (Leiden University, The Netherlands), Garrelt Mellema (Stockholm University), and NASA/ESA.

Mostly Mute Monday: The Double-Jet Death of Sun-like Stars

Occasionally, a star will blow off its outer layers in a sphere. The vast majority don’t, and ours probably won’t, either.


“The self-same atoms which, chaotically dispersed, made the nebula, now, jammed and temporarily caught in peculiar positions, form our brains; and the ‘evolution’ of brains, if understood, would be simply the account of how the atoms came to be so caught and jammed.” -William James

When stars like our Sun, between 40% and ~800% of our mass, run out of hydrogen in their core, they start to die.

The bipolar planetary nebula PN Hb 12, the late stages of a dying Sun-like star. Image credit: NASA, ESA; Acknowledgement: Josh Barrington.

The core contracts and heats up, causing the outer layers to expand as the star becomes a helium-burning red giant.

The Egg Nebula, a proto-planetary nebula in the early stages of formation. Image credit: NASA / Hubble.

The intense stellar winds produced gently blow off the star’s outer layers.

The red rectangle nebula. Image credit: ESA / Hubble & NASA.

When the core runs out of helium to burn, the central region contracts to a white dwarf, producing intense ultraviolet light.

The Southern Crab Nebula (He2–104) in its entirety, as observed by the Hubble Space Telescope. Image credit: ESA / Hubble and NASA, STScI.

This light ionizes the atoms that had previously been blown off. As the electrons recombine with their ions, they emit light of various wavelengths.

Nitrogen, hydrogen and oxygen are highlighted in the planetary nebula above, known as the Hourglass Nebula for its distinctive shape. Image credit: NASA/HST/WFPC2 R Sahai and J Trauger (JPL).

Hydrogen tends to glow red, while oxygen, sulphur, sodium, carbon and nitrogen cover the greens, blues and yellows when shown in true color.

The Ant Nebula, also known as Menzel 3. Image credit: NASA, ESA & the Hubble Heritage Team (STScI/AURA); Acknowledgment: R. Sahai (Jet Propulsion Lab), B. Balick (University of Washington).

Some 80% of planetary nebulae are asymmetrical, with the vast majority of those showing a bipolar form.

The Rotten Egg Nebula. Image credit: NASA / Hubble.

These twin jets emerge along the parent star’s rotational axis, where streams of material most likely flow outwards and collide with previously blown-off stellar layers.

The Butterfly nebula, perhaps the most beautiful of them all: Planetary Nebula NGC 6302. Image credit: NASA, ESA and the Hubble SM4 ERO Team.

Observations of active nebulae show that ~10 lunar masses worth of material are ejected each year, at speeds reaching 5% the speed of light.


Mostly Mute Monday tells the story of a single astronomical phenomenon or object primarily in visuals, with no more than 200 words of text.

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