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| Image credit: NASA/ESA Hubble Space Telescope |
Much like the jets of water being sprayed from a spinning sprinkler head, the result is an expanding pinwheel spiral when viewed from above.
Through blind cosmic luck, we are also looking LL Pegasi from above, so as the stars orbit, we can see a perfect gas spiral expand into space.
Planetary nebulae are created during the final stages of stellar evolution. For stars from half to eight-times the size of our sun, once they run out of hydrogen fuel, they start to burn heavier and heavier elements. During the latter stages of this process, they swell and the outer layers of the star are stripped away into space. This escaping gas and dust forms the nebula.
In this image, the central stars cannot be seen as they are smothered in obscuring material belching from the dying star, but the nebula has only just started to form.
According to the Hubble press release (where high resolution versions of this image can be found), the gas is being flung into space at a speed of 50,000 km/hour (about 30,000 miles/hour) and astronomers have calculated that the two stars must be orbiting each other with a period of 800 years.
