Researchers from the Institute of Astrophysics of Andalusia (Spain) have discovered an unusual evolution of the central star of a planetary nebula in our home galaxy. This discovery sheds light on future evolution, and more importantly, on the fatal fate of the Sun.
As part of their research, astronomers studied two objects: the planetary nebula HuBi 1 (shown on the left) and the planetary nebula Abell39 (visible on the right). Abell39 is a typical case of a spherical nebula surrounding a bright central star (white dwarf). This nebula is rich in ionized hydrogen.
HuBi 1, its central star underwent an event in which metal-rich material from one envelope passes into another envelope. The result is a double shell structure - a hydrogen-rich outer shell and a nitrogen-rich inner shell.
Several teams of astronomers from Spain, Hong Kong, Argentina, Mexico and Germany who have discovered the unusual evolution of the central star of the aforementioned nebula have submitted a progress report in the journal Nature.
By studying the planetary nebula HuBi 1, which is 17,000 light years away, scientists have seen that its inner regions are less ionized than the outer ones.
Analyzing the central star, with the participation of leading theoretical astrophysicists, the authors of the study found that it is surprisingly cool and rich in metal. The progenitor of this star is a low-mass star with a mass of only 1.1 of our Sun.
The authors speculate that the inner nebula was agitated by the passage of a shock blast caused by the expulsion of the stellar at a later stage of evolution. The stellar material cooled to form circumstellar dust, obscuring the star itself. This explains well why the optical brightness of the central star has declined rapidly over the past 50 years. In the absence of ionizing photons from the central star, the outer nebula began to reunite. The authors conclude that because HuBi 1 had about the same mass as the Sun, this discovery provides us with an understanding of what could happen to our solar system.