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July 2002

RXJ 2117+34 - A Preview of the demise of our Sun

This glowing nebula surrounds a very hot compact star that represents the distant future of our Sun.

Once stars like our Sun have exhausted all of their available fuel, they expand to huge diameters (as big as the orbit of the Earth). Then, their outer layers are gently ejected into space. The remnant hot core energizes the surrounding gas, producing a "planetary nebula". This is a very brief phase - lasting just 100,000 years, after which the nebula disperses and the core cools.

Lying in the summer constellation Cygnus (The Swan), RXJ 2117+34 is a remarkable example of a planetary nebula: the gas surrounding the star extends for 15 light years, making RX J2117 the largest such planetary nebula known in our Milky Way Galaxy.

Because of its large size (nearly half the size of the full moon) and faintness, it lay undiscovered until imaged by the wide field CCD camera at Fick Observatory. Discovery of this nebula gave Fick the distinction of being the smallest something to discover the largest anything!