Pluto was, until 2005, the farthest known planet from the Sun -- except for a twenty-year period in its 248-year orbit when it is nearer than Neptune (1979-1999 was the last such period). Its distance from the Sun varies between 4.4 and 7.4 billion kilometres (29.7 and 49.3 astronomical units, or AU, where 1 AU is the mean distance of the Earth from the Sun, or 150 million km).

When Pluto appears in Barron's stories, it is most often as a signifier for “object at the outer limit of the Solar system” (and therefore very far), or the last signpost on your way out of the solar system, than as location in its own right.


I close my rheumy eyes and see a tinsel and sequined probe driving out, out beyond the cold chunk of Pluto. A stone tossed into a bottomless pool, trailing bubbles. (“Shiva, Open Your Eye”)


The connection was weak, a transmission from the dark side of Pluto. Batteries were dying.  (“Proboscis”)


“The voyage was—is—scheduled for an eighteen-month loop around Pluto and back. A peek over the edge of our solar system and into the void. Even if Nancy collected data without interruption from every onboard camera and sensor, the crystals possess redundant storage capacity to function for many decades. Saturation should not occur. It defies reason.” (X’s For Eyes)



Presumption is a leading cause of death,” Labrador said. “Are you aware of NCY-93’s intended destination?”
“Why do I suddenly have a premonition you’re going to tell me something other than ‘to photograph Pluto?’” Mac said.
“On the contrary. That is precisely the mission the probe will embark upon in T-minus six days. Continuing with the thesis we are describing a hypothetical event . . . Unfortunately, NCY-93 never arrives. Her sub-light accelerator, based upon oscillation technology your grandfather shamelessly stole from Tesla, malfunctions. Cavitation causes a cascade failure in the onboard computer. The probe catapults beyond our solar system and, as far as we can recreate these circumstances, she careens into the event horizon of a black hole, and from there, plunges into the Great Dark.” (X’s For Eyes)


In a few stories, references to Pluto are actually references to H.P. Lovecraft’s tentative identification of the planet with Yuggoth (sometimes explicitly so), a (fictional) planet at the edge of our solar solar where a fungoid alien species known as the Mi-Go have a base of operations.


The Mushroom Man mission? To liquefy our insides and suck them up like a kid slobbering on a milkshake, and pack our brains in cylinders and ship them to Pluto for R&D. (“Vastation”)


Fiction. The CIA had its hands full developing a smallpox delivery mechanism at the time. Yes, mind control and pharmacology were the original hot topics down at R&D, as the MKULTRA project testifies. Yes, there was a fungus involved and, yes, numerous villagers went berserk. However, it was simply a batch of bad bread that gummed the works. The baker’s snot-nosed assistant fell asleep at the wheel, as it were. Blame him. Not the CIA and certainly not H.P’s bat-winged pals from icy Yuggoth. Pay no attention to rumours about them. No government has ever made contact with an alien species, much less colluded with it regarding human experiments. It was the baker’s apprentice in the mill with a sack of moldy flour. (“Gamma”)


“It’s going to do for the antinatalists what Ron Hubbard did for the whack jobs waiting to be whisked to Yuggoth by the ETs,” John said. (“More Dark”)




Pluto, the planet, was named after Pluto, the Roman god of the underworld (the Greek Hades). The name appears in this context in a few stories.


“Am I dreaming? Trapped inside my headset? I doubt my luck is that good. Could this be a land of eternal darkness? The River Styx leadin’ us toward Pluto himself?” (X’s For Eyes)


“With Wesley’s death, I am free.” He grunted. “I was his slave. That was the price to pay for bringing me back from the underworld. He’s King Pluto, our man Wes.” (Man With No Name)


Basement expands deep into the hillside, ancient bear den, crumbled arches, moldering catacombs, bat roosts, portal to Pluto’s Ballroom. (“Slave Arm”)


The Tooms family home sat atop a hill with views of everywhere. Three stories plus the unfinished basement — the Bear Den; Pluto’s Ballroom. (Tomahawk Park Survivors Raffle)



In 2005, Eris was discovered. It is a body 27% more massive but slightly less voluminous than Pluto, and up to three-times farther out from the Sun (37.9 to 97.7 AU). This led to Pluto’s demotion in 2006 from planet to dwarf planet, a category which also includes Eris, Haumea (a Kuiper belt object, 35 to 51.5 AU), Makemake (the largest Kuiper belt object, at 38.6 to 52.8 AU), and Ceres (the largest object in the asteroid belt, at 2.5-2.9 AU).

The Kuiper belt is a disc along the ecliptic that extends from 30 to 50 AU from the Sun, and is similar to the asteroid belt, only 20 times wider and 20 to 200 times as massive. It consists mainly of small bodies largely composed of volatiles (methane, water, and ammonia ice). It is home to three dwarf planets, as described above, which are composed of rock and metal.

The scattered disc is a sparsely populated disc which contains icy minor planets in unstable and eccentric orbits, with closest approach being in the 30 AU range and extending as far as 100 AU (15 000 000 000 km). The orbits are often much farther above and below the ecliptic. It is thought to be the source of most periodic comets.

Beyond that is the heliopause, the outermost edge of the heliosphere – the bubble-like region dominated by the Sun. The boundary is the point where the pressure of the plasma driven by the solar wind is balanced by the pressure of the interstellar medium (the matter between the stars, an extremely tenuous sprinkling of hydrogen and helium atoms, dust, and cosmic rays, hardly distinguishable from a vacuum). This is at approximately 121 AU. 

The Voyager I probe, launched in 1977, crossed the heliopause in 2012 and its twin Voyager II, launched the same year, is due to cross into interstellar space in 2019 or 2020. Both are still transmitting. Pioneer 10, launched in 1972, and Pioneer 11, launched in 1973, are thought to be 114 AU and 90 AU from the Sun, respectively, and will eventually leave the solar system as well, though they are no longer functional.

Beyond that is where the Oort cloud is theorized to be (between 50,000 and 200,000 AU). This would be a spherical cloud of icy planetesimals loosely bound by the Sun’s gravity. Objects within are easily affected by the gravitational pull of passing stars and the galaxy itself, and their perturbed orbits may send them toward the inner solar system (where they become comets).


The magic lantern crashed through the window and sailed on, shutters shuttering, frail beams of blue and red and yellow rotating, a satellite launched beyond the solar system and into deep space. (“Six Six Six”)



Following the discovery of Neptune in 1846, there remained discrepancies in the orbits of the gas giants which could be accounted for by the presence of another, as-yet-undiscovered, planet. Astronomer Percival Lowell began an intensive search for this hypothesised body, which he termed Planet X, in 1906. He died in 1916, but Clyde Tombaugh, working at the observatory Lowell founded, discovered a new planet in 1930. It was named Pluto (PL for Percival Lowell), and we’ve already discussed it.

Pluto was not sufficiently massive to be the sought-after Planet X, so the search continued. In the mean time, a revised estimate for the mass of Neptune and a recalculation of its gravitational effects on Uranus led to the disappearance of the supposed discrepancy mentioned above. Planet X was no longer needed. However, the idea has been appropriate by the fringe, and there is today a sizeable number of people who believe that there is a large undiscovered planet at the edges of the solar system which may be responsible for periodic extinction events on Earth through its disruption of Kuiper-belt or Oort cloud objects and a resulting increase in the number of cometary/asteroid impacts on our planet. Zecharia Sitchin’s Nibiru is another candidate for Planet X, among a certain crowd.

Planet X is an important plot point in Tomahawk Park Survivors Raffle.


After about fifteen seconds of listening to bug noises, Jimmy said, “What in the hell am I hearing?”
“Beetles. A whole bunch of beetles. Linwood told me insects are acting strange — ant supercolonies, bee die-offs…said it has something to do with a solar alignment affecting electromagnetic fields. Planet X…” (Tomahawk Park Survivors Raffle)


“Those who speak of it, speak quietly, because it is forbidden. Planet X…Oh, you are familiar with this theory?”
“Uh, I’m not sure whether...”
“I won’t take offense. This is your education.”
“I’ve heard of it. I mean, Planet X isn’t a secret. You said it yourself, though. Nobody thinks there’s a killer planet out there. Fun to noodle around, like UFO theory and crop circles.” (Tomahawk Park Survivors Raffle)


Mr. Speck nodded and his face tipped into the light, then darkness. “In the relative near future, Planet X, with a mass thirteen times that of Earth, will heave in its long orbit beyond Pluto and disrupt the delicate stream of the Kuiper Belt. The gravity well is immense. Planet X drags a tidal wave of debris in its wake. Imagine this tidal wave of space debris directed toward your solar system.” He traced a line from the edge of the napkin toward its center and circled back. “Pack an umbrella because it will rain shit down like you’ve never seen.” (Tomahawk Park Survivors Raffle)


Nemesis is a hypothetical brown dwarf star postulated to be orbiting the Sun at about 95,000 AU, beyond the (hypothetical) Oort cloud, to explain the perceived periodicity of mass extinctions in the geological record. The cycle of 26 million years for extinction events (based on 12 events identified in the past 250 million years in a 1984 paper), some of which coincided with large impact events, and the proposed companion star which, though undetectable, periodically disturbs Oort cloud objects and sends them on a collision course with Earth, are both unconfirmed, and considered highly doubtful.


Its position at the edge of the solar system, and at the edge of plausibility, make it perfect for inclusion in fiction.


The ha-ha part is, that “hypothetical” rogue star would’ve done that job down the road when it kicked loose that planet-killer asteroid and sent her tumbling our way. Every twenty-six million years. Look at the Yucatan; look at the Grande Coupre. Just look. Every twenty six-million years. Like a clock. Goodbye, lizards great and small; goodbye fish; goodbye, you little troublemaking primates. Goodbye.
    Except, it wasn’t, isn’t, goodbye this time around. It was hello, baby. The living and the dead and those in between all merged. Separation no longer exists. Gives the old phrase “stuck on you” an entirely fresh definition. May as well resign myself to my new niche on the food chain. I got the feeling nothing is going to change until Nemesis swings by again. (“Gamma”)


While technological and scientific advances make new discoveries at the edge of the solar system possible, and hominids each year push back the frontier of the unknown, the outer regions of our home system are still mostly terra incognita. The process of discovery is both exciting and terrifying, a fact which writers who traffic in cosmic horror, both the fictional and the purportedly non-fictional kind, have obviously noticed.