Black Holes

Black holes play a significant role in the prologue of When Stars Collide, and there are several glossary entries related to black holes and their phenomena, which have been compiled here for ease of use.

### Stellar Mass Black Hole

A stellar mass black hole is a black hole formed by the gravitational collapse of an extremely massive star. Unlike supermassive black holes found in the centre of galaxies, stellar mass black holes have masses ranging from about 5-100 solar masses (solar mass being the mass of Earth's sun). This collapse is usually observed as a hypernova explosion (a particularly energetic supernova).

Rotatin black holes contain a ring-like singularity which can be safely traversed, unlike the point-like singularities of a non-rotating black hole.

All black holes that are surrounded by intense tidal forces are prone to unexpected x-ray bursts, and are capable of obliterating any matter that comes near them. In addition, the intense gravitational forces bend space-time, causing extreme time dilations (slowing down of time) near the event horizon.

Ships are only able to safely enter and exit with the use of an E.M. Drive.

### Ergosphere

The ergosphere is a region located outside a black hole's outer event horizon. The outer surface of the ergosphere is called the static surface or static limit.

This is because world lines change from being time-like outside the static limit to being space-like inside it.

### Singularity

A gravitational singularity is a condition where gravity is so intense that spacetime breaks down and can no longer be determined by "where" or "when".

In a non-rotating black hole (Schwarzschild black hole), the singularity occurs at a single point, but in a rotating black hole (Kerr black hole), the singularity occurs on a ring.

### World Line

Also called a geodesic. This is a straight line traced by all particles in the universe. A being's world line is their Path through the cosmos. Essentially, a world line of an object is the sequence of spacetime events corresponding to the history of the object.

Upon entering a black hole, all world lines lead into the singularity and whatever fate awaits there, unless a ship is encased in an Operium Cloud to stay connected to their external world lines, allowing them to backtrack and exit the black hole.

### Dimensional Sphere

Small 'pocket dimensions' that exist beyond the singularities of rotating black holes. They sometimes hold rare materials but can also house dark worlds.

Most people who go 'diving' are searching for a dimensional sphere.

Veleians have other uses for dimensional spheres, including creating artificial ones that can be locked, organized, and programmed with specific properties.

Wil Nymera has one as a 'closet', and all of Veleian space has been locked away inside one.

### Dark World

Dark Worlds are some of the most mysterious bodies in the known universe.

They exist beyond the veil of a black hole's event horizon and inside the dimensional spheres found there, but fewer than 1 in 100 stellar mass black holes contain them.

Dark Worlds can be of any planetary type, but most of them are barren and posses strange physical qualities. While no society has ever been found on one, there are occasionally lifeforms (both plant and animal).

How these organisms are able to live within dimensional spheres is still unknown. Bio-samples are often taken from these worlds when they are found in order to discover how they're able to thrive there. Because many of them require very specific conditions to survive, the UA has outlawed taking live animals from Dark Worlds.

The only sanctioned bio-samples are plant.

There have been remnants of technology found on them before, indicating maybe some Archaean species have explored them before.

The Travel Guild has an entire internal department dedicated to studying any dark worlds found and logged away by guild or independent ships.