Helium-Shell Flash

The Hubble Space Telescope captured this image of the Stingray Nebula, the youngest known planetary nebula. In this image, the bright central star is in the middle of the green ring of gas. Its companion star is diagonally above it at 10 o'clock. The red curved lines represent bright gas that is heated by a "shock" caused when the central star's wind hits the walls of the bubbles. The nebula is as large as 130 solar systems, but, at its distance of 18,000 light-years, it appears only as big as a dime viewed a mile away. The colors shown are actual colors emitted by nitrogen (red), oxygen (green) and hydrogen (blue).
NASA

Watch a Star Evolve in “Real Time”

The odd behavior of a star in the heart of the Stingray Nebula provides tantalizing evidence that we may be seeing, first-hand, its helium-shell flash: an explosive phase of nuclear burning at the end of a star’s life.