Artist's rendition of Pioneer 11 exiting the Solar System.

Item #: SCP-4313
Object Class: Euclid
Special Containment Procedures: Six monitoring probes, each equipped with ectoilluminator equipment,1 are in orbits that pass by several known edges of SCP-4313. Thrusters are to provide any course corrections necessary after ectoplasm collisions. All probe control is to be performed remotely — no Foundation personnel are permitted to approach or enter the anomaly.
In cooperation with NASA, coverups regarding the phenomena surrounding the Pioneer 11 space probe have been disseminated. Details on Pioneer 11's acceleration changes were altered to appropriately match the non-anomalous ones experienced by Pioneer 10 due to radiation pressure.
The Overhead-ZETA monitoring probe is following a parallel trajectory to SCP-4313-Z through interstellar space, dispatched to observe projectile bursts from the anomaly. Foundation coverup protocols are in place to attribute related high-energy particle bursts to other astronomical phenomena.
As SCP-4313-Z's behavior does not impact the Solar System, no further containment for it is necessary.
Description: SCP-4313 is the remnants of an extraterrestrial gigafauna, orbiting 20-25 astronomical units (AU)2 from the sun. The body is entirely translucent, preventing accurate research into its anatomy,3 and is composed of clouds of ectoplasm, which collide with any objects or spacecraft passing through them.
In addition to the ectoplasm, SCP-4313 contains high concentrations of non-corporeal metaphysical detritus, visually seen by observers within the anomaly's borders as luminescent cyan viscera. Detritus that collides with any sapient subject merges into their body and subsequently disintegrates. This process results in the subject being implanted with variable emotional memories and sensations, believed to have originated from SCP-4313 prior to its death. Recorded memories have included:

Limb severance.
The sense of being pursued.
Panic.
Repeated impalement.
An inability to speak.
Plummeting from an extreme height.
Disorientation; loss of mental concentration.
Exsanguination.
Silence.

This is often accompanied by reported imagery of abstract shapes and impossible colors. Confusion resulting from subjects temporarily believing that they are extraterrestrial gigafauna is common.
Larger metaphysical constructs exist in the form of ten SCP-4313-Y instances. To observers inside of SCP-4313, these are viewed as elongated red cylinders, possessing a sharpened tip at one end and engines of an indeterminate nature on the other. The instances extend through the width of SCP-4313 in regular patterns, potentially in areas where organ structures used to exist. Subjects that pass through SCP-4313-Y instances claim that "no need for further chase" exists.
Discovery: SCP-4313 was first encountered by the Pioneer 11 space probe.4 On reaching a distance from 20 AU from the sun, the probe collided with SCP-4313's ectoplasm clouds and began passing through its mass. Repeated collisions caused deviations in trajectory, decelerating the probe by small but noticeable amounts.
No further phenomena was observed until Pioneer 11 reached the 21 AU mark, where probe cameras transmitted a series of images without prompting. The images show the probe's approach towards an SCP-4313-Y instance, nearing until reaching the surface. Subsequent images are of abstract shapes and memetic patterns, which, when observed, are seen as assortments of darkened limbs and hands. Contact dropped for one week before returning when Pioneer 11 exited SCP-4313. The exit process was uneventful, and all probe functions resumed as normal.

High-energy X-ray imaging of the trails from SCP-4313-Z projectiles, fired on 14/03/2040.

Addendum.4313.1: SCP-4313-Z
On 10/01/2002, soon after the radio signal of Pioneer 11 became too faint to detect, a series of high-energy X-ray bursts were detected from the probe's direction. This repeated on 10/01/2002, 26/09/2015, and on thirty dates from 2020 to 2025. The Messier-002 exploration vessel was sent to the predicted location of the probe on 23/04/2025.
Pioneer 11 was found equipped with an array of anomalous weaponry. Nine appendages visually consistent to SCP-4313-Y instances radially extended from its chassis, each ending in railguns that fire projectiles at relativistic velocities nearing 0.9c. The X-ray bursts originated from the energy released by projectile launches and the collisions the projectiles would have with the surrounding interplanetary medium. Few common trajectories for the projectiles exist. The intended targets are not known.
The SCP-4313-Z designation for the probe was established in May of 2025. Since then only one transmission from SCP-4313-Z has been recorded:

Quiet.
Stop whispering above me.
I am still hunting.

Footnotes
1. Devices that generate electric currents, interacting with ectoplasm and causing it to produce visible-wavelength light.
2. Between the orbits of Uranus and Neptune.
3. Approximate measurements from probe intersections estimate it to be between 1-2 AU wide.
4. Launched by NASA on 06/04/1973. It became the second man-made object to reach a trajectory leading outside of the Solar System.

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