This 'Born-Again' Nebula Appears to Be Inside Out

Ryan F. Mandelbaum
47 minutes ago

When some stars get old, they eject gas and dust, forming a cloud of electrically charged material in space called a planetary nebula. These nebulae all tend to have the same layered structure, but a team of scientists recently spotted a kind of planetary nebula that looks to be inside out.

The nebula, called HuBi 1, is strange, but it doesn’t defy the laws of physics—it’s a case of a planetary nebula surrounding a dim star that seems to have awaken on its way to death, emitting a shock wave that caused the nebula to look inside-out. Studying these stars could help scientists understand the evolution of stars in general.

“Everyone thought it was impossible,” study author Martín Guerrero, from the Instituto de Astrofísica de Andalucía in Spain, told Gizmodo. “But at the end, we have learned that there is a lot of physics on stellar evolution... in studying these funny things.”

Planetary nebulae are a relatively short phase in the evolution of lighter stars, lasting maybe tens of thousands of years. Lighter stars include ones the same size as to eight times the mass of our Sun. When these stars are on their way to becoming white dwarves, they eject gas or dust while continuing to emit ultraviolet radiation. The radiation ionizes, or knocks the electrons off of, the atoms in the gas. Closest to the star are highly ionized atoms, with less-ionized atoms farther away and neutral atoms in the outermost part of the nebula.

More:
https://gizmodo.com/this-born-again-nebula-appears-to-be-inside-out-1828137593