By Adam Frank
We thought we were done. It was 1992, a small restaurant in Austria. I had just presented my thesis research at a major international conference. My thesis adviser and I, along with the other members of our collaboration, were all celebrating. We thought we had solved the problem (or at least taken a major step forward).
My thesis had been a study of Planetary Nebulae - light-year sized clouds of gas that surround dying solar-type stars. In the 18th century astronomers looking through their low power telescopes (by today's standards) saw circular glowing orbs that looked vaguely like planetary disks. Nebula means cloud and the name planetary nebula (or PN for short) stuck. By 1980s astronomers knew most PN weren't round, but cigar-shaped or looked like vast cosmic butterflies. These beautiful cosmic forms were more than mysterious. What happened to stars like the sun at the end of their lives that left them which such varied tombstones? Under the tutelage of Bruce Balick of the University of Washington and Vincent Icke of Leiden University in the Netherlands I was given the job of answering that question.
Using the best supercomputers of the day we thought we had found the answer. By assuming that powerful and variable winds flow off the dying stars we could match many of the shapes seen with ground based telescopes. Begin with a slow doughnut shaped wind blown off the star. Then allow that to change to a hyperfast spherical wind as the star continues to evolve. As the fast wind snowplows through the aspherical slow moving gas a gossamer butterfly shaped nebulae is the natural result. My simulations produced models that nailed many key aspects of the data. It all worked so well. We were very happy.
Then came Hubble and everything changed.
Within a few years the HST began producing new images of Planetary Nebula that left our jaws on the floor and our minds reeling for answers. Many of Hubble's most famous images are of Planetary Nebula. HST PN images have made the cover of Newsweek, Time, National Geographic -- you name it. Pearl Jam even used an HST image of the Hourglass Nebula for a CD cover. HST showed us that planetary nebulae were a mix of symmetry and chaos, of grand design and local anarchy. The HST showed us that these light-year long objects were more beautiful than we could ever have imagined. They also showed us that we did not understand them at all. My computer models suddenly looked silly.
It's been more than 10 years since the first HST images of PN appeared. It took our field a while to get its legs back after being thrown for such a loop. Now we think we at least know what direction to look for in explaining these beautiful objects. But we still are not there yet. Our old ideas were wrong and, looking back, I am so happy for it.
That is the legacy of the HST. In a thousand subfields of astronomy like Planetary Nebulae we astronomers where given a chance to see deeper into nature's menagerie. It forced us to look on the world as children do. It forced us to renounce our cherished ideas. It forced us to think again. Most of all it renewed our respect for a Universe more creative and fecund than we could ever hope to imagine on our own.