Dragon's Egg

**Dragon's Egg** is a neutron star passing near the Solar System in the year 2050. It is the homeworld of the cheela and other nuclear-based life forms.

## Astronomical data

Dragon's Egg was formed 200,000 years ago by a supernova about 50 light-years from Earth in the constellation Draco. The supernova sent Dragon's Egg toward the Solar System at a velocity of 30 km/sec. By 2050, Dragon's Egg is very near to the Solar System, at 2120 AU from the Sun and 200 AU out of the ecliptic. It will make its closest approach to the Sun around 2350, when it will close to a distance of 250 AU before receding back into interstellar space.

Like most neutron stars, Dragon's Egg rotates extremely quickly, at 5.0183495 rotations per second.

## Physical data

As a neutron star, Dragon's Egg is extremely small, dense, and massive. While only 20 kilometers (12 miles) in diameter, it is fully half the mass of the Sun. This makes it many orders of magnitude denser than regular matter and gives the star a crushing surface gravity 67 billion times that of Earth.

### Surface & Atmosphere

Because of the immense gravity, the star's solid surface is almost completely flat, save for mountains thrown up by the star's cooling and shrinking. These mountains are very small, ranging in height from a few millimeters to 10 centimeters. The surface consists of electron-degenerate matter - normal atomic nuclei sharing an electron "sea" - at a density of 7 million g/cc. There is no liquid on the surface except for "lava" expelled from deep within the star.

The atmosphere consists solely of iron vapor. The iron vapor is highly compressed by the gravity, and only reaches a height of about 5 cm. There is no "weather" as such, and the native life does not need to breathe the iron air.

At about 8500 K, the surface and atmosphere are hotter than that of the Sun, but much cooler than the rest of the star.

### Interior

The temperature and density of Dragon's Egg increases exponentially with depth. The top of the solid electron-degenerate crust has a density of only 7 million g/cc, but at the bottom of the crust, only 1 kilometer below, the density increases by over 60,000 times to 430 billion g/cc.

Beneath the crust lies a crystalline mantle of neutrons and nuclei 2 kilometers thick. The mantle consist of neutron-rich nuclei near the top and compresses to pure neutrons near the core.

The fluid core, seven kilometers in radius and three kilometers below the surface, is hundreds of trillions of times denser than water and tens of millions of times denser than the surface. It consists mostly of superfluid neutrons, mixed in with superfluid protons and fluid electrons. At the very center, pressures, temperatures, and densities are high enough to produce more exotic elementary particles.

## Ecology

Dragon's Egg is inhabited by a native ecology based on "nuclear chemistry" involving the exchange of neutrons between nuclei in an electron sea. The native lifeforms consist of electron-degenerate matter at a density of 7 million g/cc. Producers on Dragon's Egg, analogous to plants, extract energy from the temperature differential between the star's hot surface and the cold sky. Animals on Dragon's Egg evolved directly from the plant analogues. The nuclear chemistry of Dragon's Egg proceeds one million times faster than conventional molecular chemistry, resulting in metabolic rates a million times faster than those of Earthly life-forms. This leads to very short lifespans but very fast thoughts.

Dragon's Egg is home to a sapient species, the cheela. Due to the great speed of their lives and thoughts, the cheela developed from hunter-gatherers to an interstellar civilization over the course of one month. Much of this development was influenced, observed, and aided by human explorers