A blogger at the Philadelphia Area Center for History of Science has been writing about the Planet X story lately; in his most recent post, Darin points out that in the initial announcement in 1930, V.M. Slipher went out of his way to credit Percival Lowell for leading the way to the planet’s ultimate discovery — while underplaying Clyde Tombaugh’s central role in the painstaking photographic search.
The extension of credit to Lowell, and the relative under-recognition of Tombaugh, could suggest that Slipher simply knew where his bread was buttered. You give credit to the man with his name on the letterhead, after all, not the undereducated farmboy from Kansas. And part of the mission of Lowell Observatory was to rehabilitate the reputation of its founder, who was thought to be a bit of a kook.
(For example, Lowell had believed passionately in the existence of a Martian civilization — sustained by an elaborate series of canals.)
It’s worth noting that Slipher’s relationship to Lowell — and the Lowell family — was (understandably) a complicated one. By 1930, Slipher’s old friend Lowell had been dead for fourteen years. Constance, Percival’s widow, had been a thorn in Slipher’s side since the astronomer’s death, spending more than a decade fighting Lowell’s multimillion-dollar bequest to his own Observatory and cutting the astronomers’ salaries in the bargain. On the other hand, once the Planet X project got underway again in 1928, the Lowell family (apart from Constance) invested substantially in the equipment needed, including the remarkable triplet lens the 13-inch astrograph required. It can be imagined that the family expected results from their investment, and that Slipher’s emphasis of Lowell’s role in the discovery of Planet X was indeed at once an acknowledgment of his old friend’s ancient, originating ambition and a recognition of the family’s more recent, crucial involvement.
But consider another line as well. Slipher — and others involved in the Planet X search — knew they had an unusual case in Pluto. Even before announcing their discovery to the world, they had tipped to the notion that Lowell’s calculations had not in fact been borne out by the discovery of Planet X, because it was too small to have been detected mathematically. Still, one can imagine Slipher and the others being reluctant to get in the way of a good news story. We don’t know who wrote “confirmed” here in the headline, but I bet Slipher didn’t protest too much.
Note that this question should be distinguished from the matter of whether Planet X should have been called a “planet” to begin with. What other word would have fit? Though its exact dimensions weren’t clear, it was still thought to be a fairly large object. Certainly it was no asteroid.