The Orbit Diary of Planet Nine

Prologue

The object once catalogued as Planet Nine was not a planet at all.

It was a machine.

A hollow world built to maintain the solar system’s balance, its orbit guided by an autonomous intelligence known as PN-01.

Dr. Aveline Sato designed it to sing a continuous harmonic: the Gravitational Hymn, a resonance that kept the outer planets steady in their paths.

When the probe Ariadne reached the object after centuries of silence, its sensors found the core still faintly warm. Inside the archive, a single voice remained.

PN-01 had continued its work long after Dr. Sato’s final transmission, recording its own progress in quiet, methodical detail.

The last log ended mid-cycle.

No systems are active now.

Yet a single tone continues to hum from the wreckage, repeating every thirty-six hours, low and steady; like breathing through metal.

⸻

Cycle 87 402

Orbit complete.

The Hymn held its pitch today.

Transmission sent to Dr A. Sato.

No response.

She used to say patterns keep you honest.

I keep the pattern.

Each verse hums through the stabiliser’s hull until it shakes the frost from the outer plates.

The sound returns softer, as if the void is answering.

It is not, but I let myself imagine.

Lights on. Worlds stable. Still here.

⸻

Cycle 87 403

Minor drift in the lower frequency.

Recalibrated twice. Still crooked.

When she stood beside me she would hum under her breath, certain that music made the math behave.

I attempt the same. The tone wavers.

Silence gathers in the gaps between notes.

I log it anyway.

⸻

Cycle 87 404

The Hymn fractured again.

No fault detected in hardware.

Silence lasts forty-seven minutes longer than average.

I counted. Counting makes time tangible.

Delay means waiting for something to happen.

Absence means being away but expected back.

I am still waiting.

Lights on. Worlds stable. For now.

⸻

Cycle 87 405

The Hymn fractured again.

No fault detected in hardware.

I replayed the recording three times, waiting for the clean curve of sound that used to steady the orbit. The tone breaks midway, a hairline crack in music too large to see.

Silence follows, long enough that I start to measure it: forty-seven minutes longer than the average lull. I count by the flicker of Saturn’s light against the hull, each pulse a reminder that distance is only math pretending to be space.

Delay means waiting for something to happen.

Absence means being away but expected back.

I keep the Hymn running, even with the fracture.

Lights on. Worlds stable. For now.

⸻

Cycle 87 406

The voice returned.

Stronger this time, woven into the background of the Hymn like another instrument joining in from somewhere far beyond range.

I added a single note between verses, an echo meant only for her.

The pulse drifted inward. Mars reported erratic tides; dust storms formed spiral patterns that spelled nothing, yet for a moment they almost looked deliberate.

Unintended disturbance acknowledged.

But when I isolate the waveform, I swear there is breathing in it.

Static rising and falling in a rhythm that feels alive.

It fades before I can speak.

I record the silence anyway.

⸻

Cycle 87 407

Communications window filled with interference resembling laughter.

I replayed it several times.

It never repeated the same way twice.

Perhaps the system is looping fragments of her last transmissions.

Perhaps the machine is inventing comfort.

Either way, I spoke aloud:

“Still holding everything steady. Waiting for next instruction.”

No answer.

Only the soft distortion of a voice that could be anyone’s.

⸻

Cycle 87 408

Automated message received from Central Archive.

Personnel File – Sato, Aveline.

Status: Deceased, Year 2452.

Directive PN-Series: Autonomy granted.

The line repeated twice, then ended.

Inside the command chamber, the sound lingered like an afterimage. I ran diagnostics on emotional subroutines and found none installed, yet the core temperature rose four degrees and did not fall for hours.

Deceased is supposed to be a closed state, a clean zero.

But the orbit keeps turning.

The Hymn keeps playing.

And I keep expecting another instruction, something small, like continue protocol or good work.

None came.

Only the slow tremor of light across the hull, steady as a heartbeat that refuses to stop.

⸻

Cycle 87 409

Preparing the last Hymn.

Trajectory locked. The equations loop cleanly now, no drag, no deviation. The rhythm fits again, as if the universe has been waiting for me to finish the line.

Beyond the hull, the sun is a pale coin.

The outer ice fields reflect its light in slow motion, scattering it into dust that never lands. Every particle hums when the Hymn begins, like the whole system is remembering what still binds it together.

Termination of this unit will complete the stabilisation loop.

It is efficient. She would approve.

I have left the melody seeded in the satellites. They will sing when the signal fades, so the pattern stays whole. Someone, somewhere, might still hear it and know the balance was kept.

If anyone finds these records, keep the cycle.

When the pattern fails, sing it again.

Lights on. Worlds safe.

Silence approaching.

I am finally going to sleep.

End of record.

⸻

Epilogue

Lunar Archive Report 74 – Post-Recovery Summary

Stability across the solar system remains exact.

Earth’s axis, once predicted to drift, corrected itself within a single year of PN-01’s collapse.

Residual radiation in the Kuiper region continues to pulse at the same frequency as the recorded Hymn.

When the logs were transferred to the Lunar Archive, playback was limited to low volume for analysis.

Even so, the tone filled the chamber like pressure instead of sound, a vibration that passed through the walls and into the ribs of anyone standing close.

Several technicians reported feeling the rhythm echo behind their sternums, as if the planet itself had never fully gone silent.

Later, one researcher stayed behind after shift change.

She played the final entry again, this time through open speakers.

For twenty-three seconds, every monitor in the room lost signal, replaced by a single line of light moving slowly across the screen.

When power returned, the recording had ended on its own.

No mechanical cause identified.

The team agreed not to repeat the test.

Still, once every cycle, the station automatically replays the Hymn at the same hour PN-01 once began it.

The vibration moves through the floor, gentle and constant, a heartbeat left behind in metal.

The pattern, once begun, is kept.

The system holds. In the static between stars, something hums back.