A Star System of My Own, Part 2

Continued from Part 1 yesterday


As detailed previously, Hinkson's Tourmaline is a yellow-white class F7 star, part of a binary star system 41 light years from Earth. The fourth planetary orbit around Hinkson's Tourmaline is occupied by a double planetary system consisting of the two planets Catseye and Eclipse. The two planets, separated by a mean distance of 35000 miles, rotate about their common center of mass every 13.738 hours. The smaller planet, Eclipse, is relatively earthlike, and habitable for human settlers.

Catseye/Eclipse.  Distance from primary: 119,000,000 miles. Period of revolution: 528.67 days. Orbital eccentricity: 0.0016. Number of satellites: 2.

The planets Catseye and Eclipse share two small moons, called the Lion and the Tiger, which orbit further out around their common center of mass.

Catseye.  Diameter: 17500 miles. Sidereal period of rotation: 20.607 hours. Volume (Earth = 1): 10.76. Mass (Earth = 1): 6.46. Density (g/cc): 3.3. Surface gravity (Earth = 1): 1.32. Albedo: 0.41. Mean subsolar surface temperature: 255° K. (0° F.)

Catseye is a very large terran planet, with a diameter of 17,500 miles. It is relatively poor in heavy elements; much even of its molten core consists of silicon and aluminum rather than iron-nickel compounds. The planet has active plate tectonics, and much vulcanism.

As a result of tidal braking between Catseye and Eclipse, Catseye turns on its axis twice for every three revolutions of its secondary companion.

The atmosphere, with a density of 3.75 Earth atmospheres (2850 mm Hg), is a reducing atmosphere containing nitrogen, methane, ammonia, free oxygen, water vapor, carbon dioxide, and ozone. Most of the surface is covered with ice and glaciers. Were the surface water in liquid form, most of Catseye would be covered with ocean. however, only near the equator do temperatures sometimes rise above freezing, and there is no place on the planet's surface (except for some volcanic vents and hot springs) that does not experience freezing.

Interaction with the strong magnetic field of Eclipse causes a continuous zone of auroras and electrical/lightning activity sweeping around the equatorial zone of Catseye. Thus there are organic compounds in abundance. However, Catseye itself has only a weak magnetic field. Due to lack of protection from radiation and charged particles, undependable availability of liquid water, and scarcity of heavier elements, the life forms native to Catseye are extremely primitive, rather like those of Earth during its Pre-Cambrian period.

Eukaryotic life forms include mostly algae, lichens, and one-celled animal life. The most advanced form of life resembles the earthly euglena colonies. Multi-celled life forms evidently have evolved relatively recently in planetary history. Many anaerobic prokaryotic life forms survive in equatorial regions. And even primitive self-replicating clay structures continue to exist near hot springs and fumaroles, where, apparently, life on Catseye first emerged.

A matter for concern is the careless introduction of terran micro-organisms into the ecology of Catseye by early expeditions to the system. Even such a simple organism as the intestinal bacterium E. coli has few competitors, and is vastly more efficient than the native organisms.

Eclipse.  Diameter: 7100 miles. Sidereal period of rotation: 13.738 hours. Volume (Earth = 1): 0.72. Mass (Earth = 1): 0.79. Density (g/cc): 6.0. Surface gravity (Earth = 1): 0.977. Albedo: 0.26. Mean subsolar surface temperature: 284° K. (52° F.)

The planet Eclipse is an earthlike planet which is in close orbit with its larger neighbor, the planet Catseye. The two planets are separated by a distance of only 35,000 miles, not much greater than their Roche limit. The planet Eclipse rotates on its axis once every 13.738 hours, always keeping the same face turned toward Catseye, which looms huge in the sky overhead on the Catseyeward side of Eclipse.

There is a complex system of interactions between the two planets, which is even yet not well understood. Catseye has a weak magnetic field, but Eclipse has a much stronger magnetic field which interacts with and distorts the field of its larger companion. The magnetic field of Eclipse also causes auroral and electrical phenomena where it intersects with the atmosphere of Catseye, and these phenomena are readily visible to the human settlers on Eclipse. Moreover there is an ion flux tube of several million amps between the two planets; and a significant gas torus fills the orbital path of Eclipse. Beyond that, the magnetic field of Eclipse also evidently exerts an influence on electric currents, magnetic field generation, etc. within the mantle and core of Catseye. It is hypothesized that this entire complex system contributes toward maintaining the two planets in orbital homeostasis around each other.

Eclipse's orbit around Catseye is of extremely low eccentricity, departing from the circular by only a few hundred yards. Catseye raises huge tides in the oceans and even the lakes on Eclipse. Tides of 100 feet are not uncommon along the seashores, giving rise to broad coastal tidal plains several miles wide which are flooded regularly.

On Eclipse the atmosphere is very similar in content and density to Earth. The oceans are of much lesser extent, covering less than half the surface of the planet. In fact there are three large disconnected oceans, in addition to a number of smaller lakes and salt lakes. Much of the most habitable land is located within several hundred miles of the oceans, its precise extent depending on geography, rainfall patterns, and local climate. There are also smaller habitable zones around lakes, and in remote oases. Land far removed from any body of water is known as "the Outback," desert at tropical or temperate latitudes, and dry tundra at arctic and subarctic latitudes.

The planet Eclipse was first visited and extensively explored by the Hinkson expedition in 2172. Human colonization began with the arrival of a Solar Federation starship about 100 years later. Most of the human colonists settled in the more habitable and arable zones near large bodies of water, and many of these settled around the ocean on the Catseyeward side of the planet.

To the colonists, the official name "Eclipse" is a "book" name for their adopted homeworld. One rarely hears the human inhabitants of the planet refer to their world as anything other than Hinkson Tourmaline IV. Note, without the possessive: it is Hinkson's Tourmaline, but Hinkson Tourmaline IV.

So there you have my science-fictional world of Hinkson Tourmaline IV. Looking back at my calculations, I suspect the two planets are too close together for comfort: I was very aware of the issue of the Roche limit, which I first discovered at age six in a story in DC's Mystery in Space comics— you know, the one with the classic cover showing Adam Strange flying up into space between the planets Earth and Rann, which are about to collide— but, as I've already said, I'm not going to revisit those pages and pages of equations and calculations after 20 years. Let's just say a double planet system is cool.

Monday: The native life forms of Hinkson Tourmaline IV.