A planetary nebula within a cluster

The planetary nebula NGC 2818 in its parent star cluster. Both the nebula, a luminous cloud of matter ejected from a dying star

The planetary nebula NGC 2818 in its parent star cluster. Both the nebula, a luminous cloud of matter ejected from a dying star, and the cluster are about 10,000 light-years away in the constellation Pyxis. Such a loosely bound star cluster would usually disband before one of its stars threw off a nebula, making NGC 2818 a relatively rare sight. This composite, false-color image, requiring two hours of exposure time on Hubble’s Wide Field Planetary Camera 2, was made by assigning colors to different emission wavelengths: red for nitrogen, green for hydrogen and blue for oxygen.

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