This is a composite colour Hubble image of NGC 6751, a planetary nebula with complex features. It is 6,500 light years away in the constellation Aquila. The diameter of the nebula is around 0.8 light years (600 times the size of our solar system).
The colours represent the relative temperatures of the gas; blue, orange and red indicate the hottest to coolest gas. The streamer-like features of the nebula were created by winds and radiation from the central star, which at 140,000°C is rather hot.
The name planetary nebula is something of a misnomer. Planetary nebulae are shells of gas ejected by Sun-like stars nearing the ends of their lives. This gas ejection exposes the hot stellar core; the ultraviolet radiation causes the gas to fluoresce as the planetary nebula.
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