From Ethan Siegel
May 30, 2016
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.
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…
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