Diamond ring shape formed by dead and living stars

Unusually round, planetary nebula Abell 33 aligns with foreground star

STAR DEATH  The expanding shell of gas from a dying star, called Abell 33, glows blue. The bright star on the edge of the ring sits about one-third of the way between Earth and the nebula. 


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.

Christopher Crockett is an Associate News Editor. He was formerly the astronomy writer from 2014 to 2017, and he has a Ph.D. in astronomy from the University of California, Los Angeles.

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