IC 418 has the more common name: The Spirograph Nebula, and it's easy to see why, thanks to the image provided by the Hubble Space Telescope. This unique planetary nebula1, 2,000 light years2 distant in the small southern constellation of Lepus 'the Hare', looks like it has been designed using the educational toy!
A spirograph is a drawing tool which produces geometric patterns. One tooth-edged plastic shape is firmly fixed with pins to paper on top of a solid base like cardboard; then another, unfixed, toothed shape is rotated around the fixed piece. A pen or pencil inserted into a hole on the second piece creates the pattern on the paper.
How the Spirograph Nebula Formed
Stars convert hydrogen to helium over time, and a few million years ago IC 418 was probably a yellow main sequence star similar to our own Sun. As it ran out of fuel it expanded to become a red giant star. When it reached a maximum size, it threw off its outer shell, like a cosmic butterfly emerging from a fiery spherical cocoon. What was left of the star shrank to eventually become a white dwarf3 whose energy emissions are causing the thrown-off gas to glow. All of which leaves us with an expanding, aesthetically pleasing nebula.
Astronomers do not know for sure why the Spirograph Nebula's gaseous shell is forming like this. When they don't know something they furnish us with their best guesses. One theory is that the central white dwarf, catalogued ZZ Leporis, whose brightness varies unpredictably over several hours, is emitting super-strong solar winds4. Because the change is erratic, this could be what is causing the patterns, but we don't know for sure.
Who Discovered the Spirograph Nebula?
The Spirograph Nebula was discovered in 1891 by Scottish astronomy pioneer Williamina Fleming (1857 - 1911) while she was working for Professor Edward Charles Pickering (1846 - 1919), director of Harvard College Observatory. However, it is not registered to her anywhere else but the Harvard College records. It was the done thing at the time to credit the director, or another well-known astronomer, unless otherwise instructed5.
Dreyer and Pickering
John Louis Emil Dreyer, director of the Armagh Observatory from 1882 to 1916, was compiling the New General Catalogue, bringing together the major discoveries of William Herschel and other long-gone astronomers. Newer findings were included in his Index Catalogue (the IC). As new discoveries were made, the findings were compiled and forwarded to Dreyer, who assigned the catalogue numbers and registered their discoverers. It would have been unusual if Dreyer had credited Fleming with her discoveries before she made a name for herself. Dreyer attributed the discovery of IC 418 to Professor Pickering, registering it as PK 215-24, which is still retained today. However, Fleming was the first scientist in history to measure and describe it, and log it as HN 69 (HN stands for Harvard Nebula).
In 1899, the title of Curator of Astronomical Photographs was awarded to Fleming, the first time such a position had been given to a woman. She was made a member of the Royal Astronomical Society of London on 11 May, 1906.
This Will Happen to the Sun
The Universe will not divulge all of its secrets, but meanwhile continues to astound us with glorious optical treats as our technological capabilities have advanced to provide us with marvels like the Hubble Space Telescope. Thanks to being able to study other stars and nebulae with such clarity, astronomers predict that one day our Sun will swell to become a red giant star as it runs out of fuel. By that time it will have swallowed Mercury, Venus and the Earth6. When it can't expand any more, it will cast off its outer shell of gas, creating a unique nebula. What is left of our Sun will shrink to a white dwarf, encased within the nebula.