Vulcan

The second planet of the Solar System, **Vulcan** is a large, predominantly silicate planet perched on the outer edge of the Handmaiden Belt between the orbits of Hestia and Mercury. Vulcan was colonized by Humans at the close of the Theian War for Independence and is thus a founding member of the United Nations of Humanity. The planet is extremely hot and lacks a moon system.

## Physical Characteristics

The innermost rocky planet of the Solar System, Vulcan is a searing world with all but the barest touch of an atmosphere clinging to the barren plains and lava fields. Its surface is cracked and rifted due to tidal forces from its elliptical orbit around Sol, giving it many unique cracks in its surface. It has significant geological activity, such as volcanism and possibly limited plate tectonics, although the visibility of its affects is rare.

### Internal Structure

Vulcan's structure is divided into three main regions: The paper-thin crust, the silicate mantle, and the metallic core. The crust does not cover the entirety of the planet with several large rifts spilling magma onto the surface. The mantle is divided into a partially molten upper zone, and a relatively thin, pressure-solidified lower zone, and the core consists of a thin layer of liquid iron and nickel over the rest of the solid core, which takes up roughly 40% of the internal volume of the planet. At the very center of the planet may lie an anisotropic "innermost inner core" of similar composition, but a different and currently unknown structure, to the inner core.

## Orbit & Rotation

Vulcan's orbit resides just beyond the main Handmaiden Belt, with a high eccentricity somewhat higher than that of Mercury. The planet's inclination is relatively low however, at only a few degrees. Vulcan's rotation is decoupled from its orbit, and is thus not in tidal lock. However, it is believed to be approaching it and will enter tidal lock within the next billion years.

## History

Vulcan is clearly visible in the night sky shortly before sunrise and after sunset, although its extremely close proximity to Sol makes it quite difficult to detect under normal circumstances. Vulcan was still known to the ancients as the daughter of Hestia and the guard of the Central Fire that lit the universe, but very little would be learned about it until the invention of the telescope.

The telescope brought revelations about the planet, revealing its subtle night-side glow unique to itself and not seen on the planets beyond, which would later be resolved into the many lava-filled canyons of the planet. *Mariner 12* conducted several flybys of the planet partly in an effort to lower its orbit to reach Hestia and the rest of the Handmaiden Belt, mapping large sections of its surface. *Mariner 13* also used Vulcan to slow down from its extremely high velocity near the sun, although most regions visible to it had already been mapped. *Morning Star* set down a crewed lander and a small unmanned science station near the northern pole, which would later serve as the site of the city of Shakar upon the planet's later colonization by Humanity.

Human colonization, undertaken by the Serran Empire, began 30 years after the "mysterious disappearance" of the *Rising Moon* at Mercury. The planet remained under Serran control until the empire's collapse at the close of the Theian War for Independence, during which it did surprisingly little, existing at the far edge of Earth's sphere of influence.

Vulcan's surface was slowly covered by cities, raising its population to almost a billion with a significant Loriset minority. The domed city of Tapau was assembled within an ancient crater, the glass filtering out the vast majority of the light such that it is finally possible to walk under the sun on this planet. With the onset of the Homeworld Wars, Vulcan's presence in the United Nations of Humanity made things difficult for its population resting on the edge of the hotly contested zones of the Handmaiden Belt, with several attempts by the Loriset Intendancy to take over the planet. As the wars have now somewhat cooled, Vulcan engages in trade with Theia and its colonies regularly.

## Locations

### Shakar

The largest city and capital of Vulcan, Shakar grew around the initial landing site of the *Morning Star* in Soval crater. Much of the city resides underground in empty lava tubes, shielded from Solar radiation, with those parts poking above the ground protected by mirrored, suntracking "mushrooms". As such, Shakar's presence from orbit is less visible than one would expect from such a large city. Shakar hosts the governmental buildings, the Morning Star museum complex, the ancient Loriset district, and several other historical sites. The current chair of the UNH, Olivia Payne, was born here.

### Tapau

Tapau is unique in the deep inner system, a domed city almost completely above the ground. The material making up the dome is carefully manufactured such that it screens out the overwhelming majority of incoming sunlight, dimming the city to an average Terran summer day. The second largest city on Vulcan, Tapau has a predominantly Human population like most cities here, and contains one of the foremost centers of learning beyond Earth.