Vesto Slipher

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.


In the archives of Lowell Observatory, under the excellent guidance of archivist Antoinette Beiser, I came across this typewritten memo – in its original, a few pages long.  While it’s not clear who composed this note, someone has penciled “VM?” in the upper margin — Vesto M. Slipher, director of the Observatory.

In this memo, Slipher (probably) is acknowledging that there was some delay in the announcement of the discovery of Planet X (later Pluto).  Clyde Tombaugh found the retrograding trans-Neptunian object on February 18, 1930.  Lowell Observatory didn’t announce their findings until March 13.  This happened to be Percival Lowell’s birthday — as well as, through one of this story’s many cosmically-arranged coincidences, the date on which Uranus was first discovered.

Aside from the pleasing timing, why the delay?

As I’ve written here before, the astronomers at Lowell weren’t sure what they had.  The object was too small to be the gas giant they’d been expecting.  But their mathematics seemed to indicate that a gas giant was indeed what was out there to discover; only a very large planet could perturb the orbits of Uranus and Neptune in the way that was posited.  So they were understandably puzzled to have found a very small object in just the place that Lowell’s mathematics suggested a gas giant would be.

But what’s of interest to me in this memo is the phrase “In view of the unusual character of the discovery into which the institition [sic] and its founder had given so much in the way of effort and time we had to be content to allow the momentary gusts of emotion to blow over…”

One way of reading this goes: we’d been looking for the thing for so long, and under such pressure to find something, that we wanted to make sure we had something genuine before we said anything.

That’s a legitimate reason to hesitate, of course.

But I think, too, that it’s fair to read those three weeks as a pregnant pause, during which the astronomers decided whether to call this object Planet X or not — that is, whether the accumulated pressures of history and institutional expectation outweighed the obvious problems with the object.  It wasn’t what they were expecting.

So – should they gamble?  Should they go ahead and try to call this object Planet X?

Had it been a gas giant — had they found what they’d been expecting — I bet they would have announced it the next morning.  Instead, over the next three weeks, they took countless photographs of the object, hoping to solve their conundrum.  They never did.  And in the end, of course, they didn’t call it Planet X when they finally announced it.  They just called it a “solar system object apparently trans-Neptunian.”  It was the press that called it Planet X, and so a planet was born.

Clyde Tombaugh boarded the train to Flagstaff in January 1929.  He’d been invited by Vesto Slipher for a trial period – nobody in Flagstaff knew much about Tombaugh beyond the fact that he’d made his own telescope and was in need of work.  He came cheap, anyway — he had only a high school degree.

Clyde could indeed (as I have it in Percival’s Planet) have been carrying with him the new Popular Science Monthly, which featured articles on the “world’s greatest telescope,” the “marvels of the newest electric ocean liner”,  and, for the auto buffs, “Reverse Pliers Serve as Handy Valve Lifters.”  Clyde’s train left Larned, Kansas, on January 14, 1929 – the day after another Arizona legend, Wyatt Earp, died in a Los Angeles bungalow at the age of eighty, of chronic cystitis.  (Whatever that is.)

Clyde was nervous, of course, not knowing what to expect in Flagstaff; and well he might have been.  His future was in no way certain in Arizona.  On February 7, 1929, three weeks after Tombaugh arrived, Vesto Slipher wrote (to Lowell Observatory trustee Roger Putnam, in Massachusetts):

Mr. Tombaugh, the young man from Kansas, has been here since about the middle of January.  We think he is going to develop into a useful man.  He has several good qualities that are going to make up we think for his meager training.  He is looking forward to the arrival of the new objective and is eager to be working with it.  He has good attitude; careful with apparatus, willing to do anything to make himself useful and is enthusiastic about learning and wants to do observing.  We believe these qualities will after a time largely overcome his deficiency of schooling and training.

Slipher is not terribly impressed, perhaps.  But Clyde costs him only $90 a month, and he is awfully dogged.  So Slipher lets him stay.

Such a close thing life is, at every turn.

News traveled fast.  The day after Vesto Slipher made his announcement of Clyde Tombaugh’s discovery, papers around the world ran front-page headlines calling the “trans-Neptunian object” a “planet”.   Notice that while the cautious astronomers at Lowell Observatory hadn’t declared the object a planet themselves, the public did it for them.

You have to think Slipher knew this would be the case.  After all, finding a planet solved all kinds of problems for the observatory staff — most of all, the problems of expectation.  The Lowells, including Percival Lowell’s widow Constance, were keen to end the search with a success story.  They’d poured plenty of money, and a lot of heartache, into the project.

How terrible if Lowell had spent all those years just chasing ghosts.

(They don’t write them like this any longer, do they?)

These early reports are typically breathless.  Observations in the next few weeks would bear out Planet X’s apparently small size.  Rather than being 1200 times the size of Earth, Pluto is smaller than Earth’s moon.

One of the great thrills of my life was being hosted by Antoinette Beiser at Lowell Observatory in Flagstaff, Arizona, while I was researching Percival’s Planetand being led into the dusty basement archives of the observatory.  I wrote the following scene — which didn’t make it into the book ultimately — after having experienced something like it in person.

Here, the young Harvard mathematician Alan Barber is being taken into the observatory vaults by the Director, Vesto Slipher — and being given access to Percival Lowell’s raw calculations — the work that convinced Lowell that a 9th planet was out there, somewhere, and that led to his publication of Memoir of a Trans-Neptunian Planet

None of this made it into the novel, but the book does contain a scene — the grandchild of this scene — in which Slipher hands Pericval Lowell’s notebooks over to Alan Barber.

The papers are as I describe them here, and the boxes — and the dust.

*                      *                    *

Vesto Slipher switches on the basement light and twirls the key on its length of twisted wire.  “This way,” he nods.

The basement smells of coal dust, firewood, and developing fluid.  They walk the length of the hall to a steel door.  Alan has never seen it opened.  He has assumed it housed some of the building’s works.  Slipher works the key into the lock.  “Percy would send us these every few months, you know,” Slipher tugs the door open onto a damp, sweet-smelling darkness.  “So we ended up with quite a collection.”

He flicks on a light.  Inside is a long, low basement vault with a cement ceiling.  Junk everywhere: discarded equipment with snipped wires, motors and housings, ladders with splintered rungs, a Victorian dollhouse split open along the green-papered parlor, dead fans.  On a shelf stands a long row of slumping notebooks, crimson and emerald green.  Slipher tugs the first one from the row, careful not to send them all to the floor.

“Percy’s notebooks,” he says.

“From the Memoir.”

“That’s right.  All the figures the computers gave him went into these.  He’d finish with one and put it in an envelope and send it out.  He always thought he’d look at them when he came out, but – ”  The director places his hands in his pockets, tips back on his heels.  “You know, he’d have changed his mind again by the time he got out here.  He was very good, you know.  Just as good as anyone you’ve got there now.  But he was sort of – you know, enthusiastic.”

Alan finds it hard to speak: it is the Aladdin’s cave of Lowell Observatory.  “Some trouble,” he manages.

“Some trouble,” Slipher agrees, mildly.  He hands Alan the key.  “It’s in order.  Starting back there.  All his calculations going back thirty years almost.  Off and on.  What we have, anyway.  They’re yours, if you want them.  For whatever the hell they’re worth.”

He finds his breath.  “Thank you.”

“That’s what you think,” Slipher answers.

In another minute he is alone, in the middle of the night, still blurry with liquor.  His mouth tastes sweetly of raw spirits.  A single bulb burns in a wire cage.  At the musty back of the vault he slides down the box marked Mar 17  – 88, taking its weight into his arms.  The box is covered with dust.  He sets it on the library table, blows off the dust, tips back the cardboard lid.

Inside sits a gray paper folder, the first of a stack.  He teases his handkerchief out of his back pocket and wipes his hands on it to remove the dust, then lifts the folder out.  He sets the folder on the table.  He opens it.

Someone’s purposeful black pen, guided by a ruler, has drawn a straight line across the top of the page.  Above this line, in a curling hand, is written Jupiter – July 1793 – Maddox Obsv. Then comes a long fall of trigonometry that represents the attempt of someone in 1888 to determine whether Jupiter was where it was supposed to be, when observed doing what it was doing in 1793.

He follows the calculation with his forefinger.

Turns the page.

He follows.

He sinks into the chair, turns another page.


In an hour he has gone halfway through the folder.  At some point as though he is sitting an exam he unclasps his Santos from his wrist and sets it before him.  He has a pencil in his hand now and is making notes on the inside cover of the gray folder.  The computer, whoever she was, has not made any errors, not that Alan can find, anyway.  He admires the fine, womanly hand that falls with a sort of chiming inerrancy down the page, page after page, as she turns one, then another observation this way and that through the method of least squares, and he can’t help it, he thinks of Florence, thinks of this sort of exact feminine facility, a sort of equivalent to stitching, in that it is invisible, but an error anywhere is enough to ruin the entire effort.

All these boxes and boxes.

He looks out the door of the vault, down the empty basement corridor.  If Dick were to discover him here he would give him the business for sure.  Alan has a vision of him loping into view, trailing his fingers on the vaulted cement ceiling.

But Dick is gone.

A queer feeling comes over him that the ninth planet is truly out there somewhere.  Something in the cavey, monasterial feel of this basement tells him this.  It is a sort of sum of these variant parts: the madman who ordered all these numbers to be set down, the years of painstaking feminine labor in the walnut-paneled computer room on Halward Street in Cambridge, all the girls with their inkwells and linen blotters, plus this desert air, this piney hilltop, the crazy Injuns in their reeking blankets, their blackfly horsewagons, and the airstrip at the edge of town, the train dragging its lighted cars away.

All of it adds up somehow to a sweet little mysterious certainty.

They were a cautious bunch, V.M. Slipher especially.  Years of association with Percival Lowell’s brand of lunacy can leave you a little gun-shy.

But the “object” they’ve found is “one apparently fulfilling Lowell’s theoretical findings”.  In other words, this strange, tiny body is just where it’s supposed to be — going by Percival Lowell’s decades of residual calculations.  And it’s definitely “trans-Neptunian” — that is, it’s out past Neptune, and it’s retrograding.  And the only thing that retrogrades is something in orbit around the sun.

So what is it, if not a planet?

Thanks due to Antoinette Beiser, Kevin Schindler, Travis Marsala as Alan Barber, Kevin Strehlow as Clyde Tombaugh, and Chris Crockett (for his cameo as Vesto Slipher!) — and of course to the fine crew of Nobun Productions, without whom this book trailer etc etc.

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