The Eleventh Planet?

(In honor of current events, here, have a Pluto-analog…)

They say one is the loneliest number, but eleven is the loneliest planet. Well, it’s not a planet as such. Múrcár is, galactographically, a gelidean-class planetesimal, massing 1.7 x 10²² kg, and orbiting well beyond the system snowline at an average of 41 au.

This terminological technicality is a great relief to the Imperial Grand Survey’s Board of Nomenclature, since at aphelion, Múrcár’s orbit reaches 56 au from Lumenna, at the far outer edge of Senna’s Belt. Since the stars of the Lumenna-Súnáris System have only a 125 au separation at closest approach, the height of deep summer, they have been known to swap Sennan objects back and forth at this time; and while it has not yet been observed, astronomers believe that Múrcár’s orbit is vulnerable to this phenomenon when conditions are right. And thus the nomenclaturists would prefer, in this special case, not to have to rule definitively that Múrcár is Lumenna XI when it might be Súnáris X only a matter of mere millennia later.

The above, unfortunately, is the most interesting thing that can be said about Múrcár specifically. It is in virtually all ways a typical gelidean-class Sennan object, composed largely of ices (primarily water ice, with a surface admixture of methane, carbon monoxide, and nitrogen ice) surrounding a core of silicaceous material; it is merely the largest – and first discovered – of the objects in Senna’s Belt.

Múrcár was discovered in 1843 by Senna Marasi, an astronomer at the Starspike, during a fortuitous transit of Súnáris. While it was considered for a while the eleventh planet of the Lumenna system, further studies of the region soon showed other bodies, albeit smaller, to also exist there, similar to the e’Luminiaren. The first close-up images of Múrcár were obtained in 2099, in a fly-by by the Peregrine Ardent probe, and it was first visited in 2139, at which time a lander from Outward Bound confirmed much of the speculation about its surface conditions. The first sophont landing did not take place until 2409 (CSS Veiled In Darkness As A Gown), during an exploratory mission primarily focused upon the further-out bodies of the Shards.

Since then, Múrcár has remained essentially uninhabited. It has however, in its time, hosted:

• A temporary home port and refueling station for comet herders during the ecopoesis of Talentar;
• An astronomical observatory far from the traffic and noise of the inner system;
• A monastery, “Emptiness Dome”, for the meditative Children of the Void sect, before the construction of their present home of Blackwatch Station in Almeä System;
• A repository-vault for the Green Bytes data haven, which moved on due to Múrcár becoming too well known for their purposes;
• The primary coordination point for the Outsystem Early Warning line, until it was obsoleted by newer technologies and placed far behind the Empire’s borders after the Reunification;
• The observatory control center for the Barrascán Array (before its replacement by the Very Long Baseline Observer, itself replaced by the Super-Size Synthetic Aperture).
• A fueling station for outbound lighthuggers of the now-largely-obsolete “snowball” type.

In the present day, however, Múrcár hosts only a single automated, unstaffed, habitat and fuel station, intended for emergency use. Múrcár also serves as a gathering place, market, and communications hub for the various hermits, fringers, and other darkfolk who make their homes in the far outer system, but this activity almost always takes place in Múrcár near space, rather than on the world itself.

– Leyness’s Worlds: Guide to the Core Worlds