Unusually round, planetary nebula Abell 33 aligns with foreground star
A chance alignment of stars has created a diamond ring–like image.
Abell 33 is the ghostly remnant of a dead star, a planetary nebula about 3 light-years across and 2,500 light-years from Earth in the Hydra constellation. Like other old stars, Abell 33 inflated to many times its original size. As powerful stellar winds overtook gravity’s inward pull, the bulk of the star blew gently into space and formed the nebula. The star’s core stayed behind to become a white dwarf, a hot, compact ball about the size of Earth.
In a new image from the Very Large Telescope in Chile, Abell 33 appears as an expanding blue bubble. Ultraviolet radiation from the white dwarf, the point of light near the nebula’s center, causes ionized oxygen to glow blue. Abell 33’s nearly perfect symmetry is rare for planetary nebulae: Usually, something distorts the gas. The brilliant star perched on the edge of the nebula is a lucky accident, a chance alignment with a star sitting roughly one-third of the way between Earth and Abell 33.
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