Never trust an unstable AGB star…

The best passage from The Lord of the Rings and an astronomical reference to kick off the weekend.

An unstable asymptotic giant branch star is a low- to medium-mass star, like our Sun, in its final phase of fusing hydrogen into helium. At this point, it has burned through all of the hydrogen in its core and is only burning hydrogen in an outer layer. It becomes unstable when it begins to pulsate, after which it will puff off its outer layer into what’s called a planetary nebula. This is the fate of our Sun.

Here’s the Stingray Nebula, in case you were curious.

The Stingray Nebula. Credit: NASA, Matt Bobrowsky (Orbital Sciences Corporation).