Abell 30 planetary nebula proved to be a very challenging target. It is super faint and even with over 64 hours of OIII alone, I had to really push the data hard. Furthermore being a binary dwarf system that somehow reignited, I really wanted to make sure I did not blow out the core; even the Hubble Telescope blew the core out through X-Ray imaging.

Abell 30 is a planetary nebula, that stage in the star’s life when the two winds are colliding, and the central star is lighting them up like a neon sign. The circular shape on the outside is the giant wind, expanding away in a spherical shell like a soap bubble (and also slightly brightened along the outer edge as it rams into the thin gas between stars). It’s actually rare to get a nearly perfect circular outer halo like that, so this is neat.

But it’s those tendrils of gas on the inside that are so very interesting. What astronomers think happened here is that the dying star was reborn for a brief time. During the red giant stage, right above the core are layers of oxygen and carbon, then helium above that, and a very thin shell of hydrogen above that. The heat from below causes the hydrogen to fuse at a furious rate, creating more helium that drops down (helium is heavier than hydrogen, so it sinks). If enough helium builds up, it fuses into carbon and oxygen, but this creates a vast amount of energy very rapidly. It’s nearly an explosion, but astronomers (who love to use dull terminology to describe soul-shaking events) call this a very late thermal pulse.

Thermal pulses usually occur several times in the star’s life while the outer layers are still being ejected. But this one happens pretty late, when the layers are already essentially gone. This blows out the remaining gas around the core, creating those tendrils near the star, and the gas is moving so rapidly that when it slams into the gas around it the shock waves generate X-rays (there’s probably magnetism involved too, because there always is, and it complicates things immensely).

Since fusion is what powers a star, it’s fair to say that for a moment it was reborn. But at this point it’s more like a death rattle. We’re looking at the last gasp of a dying star.

Incidentally, all this activity in Abell 30 is very recent! The outer halo red giant wind has been expanding for about 12,500 years (spectra reveal the expansion velocity of the gas, and we can measure how big it is and its distance to get the age), while the inner gas is only about 850 years old! Given that the star was billions of years old before it started dying, we really are seeing the last sliver of its life.