THE INSIDE-OUT NEBULA
Nothing lasts forever. Even our own Sun will die eventually. It will swell into a red giant before puffing its outer layers into space to form a beautiful planetary nebula. Astronomers are confident that this is the fate awaiting our star because they have seen it happen many times before across the universe. Yet one planetary nebula in particular is causing quite a stir – it appears to be inside out.
In 2018 astronomers were studying the planetary nebula known as HuBi 1, which sits around 17,000 light years from Earth. They soon noticed something odd about the way its gas is ionised. Ionisation is the process by which electrons are stripped away from atoms to create charged particles known as ‘ions’. Normally the inner regions of a planetary nebula – where it’s hotter – are more ionised than the cooler outer shell, yet with HuBi 1 it’s the other way around. Before this discovery such a scenario was thought to be impossible.
One potential explanation is that the star briefly came back to life, creating a shockwave that moved out through the surrounding gas. The shockwave was so energetic that it passed straight through the inner gas, only ionising the outer gas.
The weird nebula may reveal the future of our sun