I'm tucking in to dinner with astronomer Alexander Wolszczan in a bustling bistro near his office at Penn State, and he’s in a cheerfully gloomy frame of mind. He has reason enough to be gloomy. He discovered the first planets beyond our solar system but gets little recognition. His follow-up research has been slow and painstaking, hitting repeated dead ends. Neither of these things seems to bother him in the least, however. No, what puts Wolszczan in his intriguingly contradictory mood are the planets themselves.
Earth leads a charmed existence, circling a stable sun that provides just the right amount of warmth for life. The planets that Wolszczan found 22 years ago aren’t so lucky. They orbit a pulsar — a tiny, rapidly spinning stellar cinder that blasts them with ferocious surges of radiation. “There could be a permanent aurora lighting up the sky there from the wind of particles from the pulsar. Some of those particles could get down to the surface and blast it smooth,” he says. And the misery of the planets’ current existence pales in comparison with their traumatic birth, in the 100-billion-degree debris from a supernova that shredded most of the original star.
More recently, Wolszczan has turned his attention to another class of doomed planets. He has begun finding and studying worlds around red giants, elderly stars that have nearly exhausted their nuclear fuel. In a last spasm of activity, they swell up, brighten tremendously and shed enormous clouds of gas. Any planets circling a red giant would get baked and buffeted in the process. That fate awaits Earth in about 5 billion years, when our sun will join the ranks of the red giants. For the distant planets Wolszczan is scrutinizing, the future is now.
These areas of research set Wolszczan distinctly apart from his peers. Since his pulsar planet discovery in 1992, lots of other scientists have joined the search for worlds around other stars, but almost nobody else does it the way he does. He half-smiles: “I’m not exactly a mainstream person.” Today’s planet hunters tend to fixate on planets similar to Earth, eagerly touting newfound worlds that even vaguely resemble our own in size, temperature or composition. My conversation with Wolszczan covers none of that.
In an even, Polish-inflected cadence, he talks not about living planets, but about dying ones, dead ones and the ones that — in the case of the pulsar planets — have entered an uneasy afterlife. I come to think of the objects Wolszczan studies as ghost worlds. They are far removed from terrestrial standards of comfort and stability. They have, in a real sense, moved from one plane of existence to another. They are celestial oddities that most of his colleagues look right past, as if they weren’t even there. All of those factors are exactly what makes them so fascinating to Wolszczan: They are the extreme cases that test the limits of how planets can form, and where they can survive.
