* Astronomy

Planetary Nebula Abell 63

Abell 63 was the first planetary nebula to be shown to host a binary central star, and has since been shown to be an archetype system. This image taken with the WFC shows the nebula to comprise a central barrel-shaped structure along with two caps of emission ejected along the major axis of the central nebula. These caps have since been shown to be older than the central regions by around 1000 years, probably forming via an episode of mass transfer between the two stars at the nebular centre before the central barrel was itself ejected. Further evidence for this mass transfer was discovered by combining observations from the Jacobus Kapteyn Telescope and the William Herschel Telescope to show that the companion star in this system has been inflated to nearly twice its normal size. This inflation is almost certainly a result of the rapid mass transfer from the primary star knocking the companion out of thermal equilibrium.
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