Researchers at Cambridge and the Complutense University of Madrid recently suggested that two planets larger than Earth might exist in the solar system, beyond the orbits of Neptune and Pluto. Skywatchers are atwitter, as well they should be. If true, this is major news.
But the scientific importance of this hypothesis may matter less than what it means on a gut level to you and me on terra firma. For the announcements, if borne out, reflect our evolving view of the firmament—and, therefore, of ourselves.
Humankind’s notion of the solar system has always been a work in progress. The geocentric ancients knew only of our neighbors from Mercury through Saturn. Who among them could have imagined that Uranus would be discovered in the 18th century, or Neptune in the 19th? Not that we of the 20th and 21st centuries are much brighter: As a child of the 1960s and ’70s, I grew up thinking that nine planets was the norm. Through textbooks and field trips to the Hayden Planetarium, I received the conventional wisdom that Pluto was the runt of the litter, a stony oddball bringing up the rear behind four gaseous giants.
Today, I don’t know what to think. For some years, various learned outfits have steadily downgraded Pluto, alternately classifying it as a “trans-Neptunian body,” a “Kuiper Belt object,” and a “dwarf planet.” It was also once gospel that poor Pluto had no moon. Then, in 1978, its satellite Charon was discovered, and several others have since been spotted. Within the past month, the first spacecraft that we have rocketed to Pluto, NASA’s New Horizons, began snapping pictures. Surely these photographs will reveal further perplexities.
Confusion exists in other planetary arenas. For centuries, we Terrans believed that Saturn alone came equipped with rings. But in the 1980s and ’90s, we learned of the rings of Jupiter, Uranus, and Neptune. We learned, too, of the weird orientation of Uranus—a heavenly body that, as the phrase goes, “got knocked on its side.”
And who knows what to make of Eris, currently deemed a dwarf planet larger than Pluto and even more distant? Or Ceres, once classified as the biggest asteroid in the famous belt between Mars and Jupiter but now upgraded (as opposed to Pluto’s downgrading) to dwarf planet status? Perhaps NASA’s Dawn spacecraft, which last month began its close-up examination of Ceres, will enlighten us.
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Admittedly, none of this taxonomy and categorizing has much to do with our waking lives. As far as most of us are concerned, we merely care about what mischief Luna could wreak on our tides and whether we might glimpse the morning or the evening star. (That’s Venus to you Earthlings.) Just the same, our continually changing view of the solar system is weirdly profound. Somehow, not quite knowing what’s hovering above our heads—quite closely, in cosmological terms—is both tantalizing and unsettling, shifting as it does our view of how we fit into the cosmos. This isn’t, after all, a matter of super-distant objects like galaxies or novae or nebulae. We’re talking about our fellow travelers who are whirling around our warm, comforting buddy Sol.
The research into the theoretical trans-Plutonian planets is still preliminary. And the Cambridge and Madrid scientists may well be proved wrong. They wouldn’t be the first. The 19th-century French mathematician Urbain Le Verrier argued vehemently for a planet he called “Vulcan,” which orbited between the Sun and Mercury. He was famously in error; no evidence has ever emerged that Vulcan exists. Still, even the possibility of unseen orbital companions can’t help but give us pause.
Parenthetically, it’s fun to consider the potential nomenclature of the latest would-be planetary gatecrashers. For the moment, they are being dubbed Planets X and Y. If confirmed, they’ll almost certainly be accorded suitably dark and classical names. “Lethe” is one that comes to mind.
In any event, the astronomical research that is currently making headlines would seem to indicate that the process of local planetary discovery is destined never to end. Arthur C. Clarke put it well, albeit inadvertently, in his novel 2001: A Space Odyssey, when he wrote that Jupiter “was constantly capturing short-lived moons from the asteroid belt and losing them again after a few million years. Only the inner satellites were its permanent property; the Sun could never wrest them from its grasp.”
Similarly, we capture notions of our solar system and lose them after a time. But never wrested from us is the music of the spheres—as well as our quest to understand it.
Thomas Vinciguerra is the author of the forthcoming Cast of Characters: Wolcott Gibbs, E.B. White, James Thurber, and the Golden Age of The New Yorker (Norton).
