THIRA SYSTEM

Thira star as seen from Earth

STAR: THIRA
Mass: 99% Sol
Diametre: 102% Sol
Luminosity: 104.1% Sol (4.34 absolute magnitude)
Temperature: 5790K (5,516°C/9,962°F)
Age: 4.5 billion Earth years
Radial velocity: 2.05km/s
Spectral type: G2V

Absolute magnitude: 4.81

This is the only star in the system. This star is orbited by 6 planets, being one gas giant 16 times more massive than Earth taking not longer than 40 Earth days to orbit its parent star; two planets are rocky (both of them in the habitable zone) and the last three being Earth-sized icy planets, very far away from their parent star. It is a yellow dwarf, main sequence star, located nearly 92.2 light-years from the Sun.

PLANETS

There are 6 planets in this star system and a very large number of asteroids and comets. Due to the relatively low metallicity of its original nebula, if we were to gather all of the objects in this planetary system, they would have a mass a slightly above the mass of Neptune (in the Solar System).

Thira's Companion and its two biggest moons

1. THIRA'S COMPANION (to be named in Hiwashazulitu later)

Mass: 9.63 x 10^25 kg (16.14 Earth)

Average density: 0.69g/cm³

Diameter: 64,380 km

Composition: 96.1% hydrogen, 2.3% helium, 1.6% other elements

Gravity: 6.11m/s, 0.62G

Rotational period: 40 Earth days (tidally locked)

Orbital Period: 40 Earth days

Semimajor axis: 34.01 million km (0.22 AU)

Eccentricity: 0.088 (31.01mi km periastron, 37.0mi km apastron)

Rotational tilt: 1.2°

Albedo: 0.662

Temperatures: ~500K (~230°C/~450°F)

Moons: 13 (mostly small rocky moons)

This is the closest planet to the star. This planet has a composition similar to Saturn’s, and it is also the least dense planet in the Thira system. Due to its proximity to its parent star, it is tidally locked to it, meaning that it has always the same side facing the star while the other side is in perpetual darkness. This creates a beautiful dark eye-shaped storm in the centre of the illuminated side, where strong winds rise to the upper atmosphere and then moves towards the opposite side of the planet, where there is another storm where the air then sinks to the lower parts of the atmosphere, with winds blowing towards the clear side, and the cycle continues.

The planet also holds the strongest planetary magnetic field in the entire system, with its magnetic tail reaching the orbit of the third planet, being comparable to the magnetosphere of Jupiter. The mechanisms behind the generation of such a powerful magnetic field on a slowly-rotating planet is unknown.

The planet also has 13 moons, 11 of which are small, asteroid-sized moons. The biggest moon is Companion’s A, which is slowly being destroyed by the tidal forces as the moon is slowly spiralling towards the planet; also, intense volcanic activity on the moon is helping spread the material for the planet’s small ring system. The second biggest moon, Companion’s B, orbits further away, and has active volcanos caused by the planet’s tidal forces acting on the moon’s core. Both moons are nearly the size of Io and Earth’s Moon, respectively.

Hiwashazu from high orbit

2. HIWASHAZU (see main page)

Mass: 7.791x10^24 (1.3 Earth mass)
Average density: 5.31g/cm³
Diametre: 14,100 km
Composition: 44.5% silicon, 28.3% carbon, 12.1% gold, 9.5% silver, 3.2% copper, 1.3% uranium, 1.1% other elements
Gravity: 1.07G
Rotational period: 27.15 Earth hours
Orbital Period: 479.584 days (544.041 Earth days)
Semimajor axis: 194.48 million km
Eccentricity: 0.0352 (144.2mi km periapsis, 154.74mi km apoapsis)
Rotational tilt: 31.4°
Surface: 76% water, 24% land; 38% polar caps
Atmosphere: 1.24atm (38.2% nitrogen, 27.8% oxygen, 26.4% neon, 6% nitrogen, 0.6% carbon dioxide, 1% other gases)
Albedo: 0.29
Greenhouse effect: 96.31% of Earth
Temperatures: 287K (14°C/57.2°F; average), 325K (52°C/125.6°F; maximum) - 189K (-84°C/119.2°F; minimum)

This planet orbits around Thira, a solar analogue in the Milky Way galaxy. It has 1.3 Earth mass, but due to its lower-than-Earth density, its gravity is just 7% stronger that Earth's. It has three small moons that orbit at an orbital period ratio of 1:4:9 starting from the closest one, which orbits at a distance of 50,087.6km (27.15hrs), the second one orbits at 126,292km (108.6hrs) and the third one orbits at 216,955km (244.35hrs). This means that every 36 days in the planet there is an alignment of these three satellites, which gave them the base for their month-equivalent period.

The planet is inhabited by humans, plants and other non-native life forms, the same found on Gelo and Keléshtevadáran. Its atmosphere is rich on oxygen and show little signs of terraforming process.

Of all known terraformed planets, Hiwashazu has the most Earth-like biosphere, since little genetic modifications were necessary in order for the plants and animals to adapt to the new environment. However, when compared to the humans from Gelo, Keleshtevadaran and other planets, the humans that inhabit this planet have been considerably modified, to the point of hermaphroditism being the norm.

3. WANDERER (to be named in Hiwashazulitu later)

Mass: 2.993 x 10^24 kg (0.51 Earth)

Average density: 5.5g/cm³

Diameter: 10,130 km

Composition: 49.1% oxygen, 24.2% silicon, 9.1% aluminium, 6.4% iron, 1.1% gold, 10.1% other elements

Gravity: 7.79m/s, 0.79G

Rotational period: 1.1 Earth days

Orbital Period: 647.5 Earth days

Semimajor axis: 218.46 million km (1.46 AU)

Eccentricity: 0.068 (203.6mi km periastron, 233.31mi km apastron)

Rotational tilt: 22.4°

Albedo: 0.273

Atmosphere: 1.06atm (62.1% methane, 23.3% carbon dioxide, 3.8% nitrogen, 3.4% water vapour, 0.9% oxygen, 4.5% other gases)

Temperatures: 285K (12°C/54°F) average; 175K (-98°C/-145°F) minimum recorded, 319K (46°C/115°F) maximum recorded

Moons: 1

This planet has a rich biosphere native to the planet. The first signs of live date back to nearly 3 billion years ago, with the first bacteria. Due to the high concentrations of methane in the planet's atmosphere, the oxygen cannot build up as it happened on Earth, and most of it reacts right away with methane to produce carbon dioxide and water vapour. The carbon dioxide produced is then captured by some species of bacteria that combine it with water by means of photosynthesis, releasing methane and free oxygen. There are a few species of bacteria that survive on oxygen, so it is common to see symbiotic colonies of both kinds of bacteria, one feeding the other. These oxygen-fed bacteria are also found to live on the leaves of plants that produce oxygen by photosynthesis. There are indications that in the next few hundred thousand years there will be a runaway oxygenation event in the planet's atmosphere caused by the ever growing biomass of photosynthetic bacteria and "algae", leading to a mass extintion much like Earth had during the early Paleoproterozoic era.
Due to the current lack of enough free oxygen, there is no large animal life on the planet; however, some species of small fish-like animals do survive on the planet, by having large colonies of oxygen-producing bacteria, as well as in flooded caves where oxygen can build up to as much as 12% of the air and be kept from reacting with methane.

The planet has a significant magnetosphere that protects the planet from stellar radiation emitted by the star. It also has active plate tectonics, with an average rate of movement of the plates around 1cm per Earth year.

Although this planet is even more Earth-like than Hiwashazu, it is speculated that the Captors did not terraform this planet in order to preserve the native biosphere. Many countries from Hiwashazu have estabilished research centres on the planet, but settling there has been forbidden; the Geloan Research Institute for "Extrasolar" Systems (RIES, for short), from the Captors System, established an autonomous research station on the planet as well.

4. FOURTH PLANET

Mass: 6.1 x 10^23 kg (0.1 Earth)

Average density: 2.1g/cm³

Diameter: 8,221 km

Composition: 39.1% nitrogen, 34.6% water, 10.3% silicates, 16% other elements

Gravity: 2.36m/s, 0.24G

Rotational period: 6.9 Earth days

Orbital Period: 12.68 Earth years

Semimajor axis: 810.832 million km (5.42 AU)

Eccentricity: 0.143 (694.88mi km periastron, 926.78mi km apastron)

Rotational tilt: 12.3°

Albedo: 0.57

Atmosphere: negligible (72% helium, 21% hydrogen, 7% other gases)

Temperatures: 99K (-174°C/-281°F) average; 107K (-166°C/-267°F) during periastron, 92K (-181°C/-294°F) during apastron

Moons: 5 (small icy moons)

This planet is the first of the icy worlds, and also is the smallest of them. There are few research bases on this planet, but most of the time it is automated and humans only set foot on them every few dozen years for maintenance and advanced research. This planet also has the deepest manmade borehole, going as deep as 21km. Spacecrafts on orbit around the planet detected a thin tail of gases being ejected from the planet, similar to a comet, mainly during a CME.The planet's orbit sometimes interlaps with the Fifth planet's orbit. It is believed that a sizeable rogue planet might have passed close to the Fourth planet several million or billion years ago, and changed its orbit.

5. FIFTH PLANET

Mass: 1.37 x 10^24 kg (0.2 Earth)

Average density: 2.8g/cm³

Diameter: 9,785 km

Composition: 38.7% nitrogen, 38.6% water, 9.9% carbon dioxide, 12.8% other elements

Gravity: 3.75m/s, 0.38G

Rotational period: 4.7 Earth days

Orbital Period: 14,4 Earth years

Semimajor axis: 882.64 million km (5.9 AU)

Eccentricity: 0.043 (844.68mi km periastron, 920.59mi km apastron)

Rotational tilt: 12.3°

Albedo: 0.29

Atmosphere: 1.4 (72% methane, 21% ethane, 7% other gases)

Temperatures: 124K (-149°C/-236°F) average; 127K (-146°C/-231°F), 122K (-151°C/-240°F)

Moons: 1 (small, asteroid-sized)

This planet has a dense atmosphere filled with hydocarbons, similar to Saturn's moon Titan. These hydrocarbons are formed by the ultraviolet radiation coming from the star, as well as from cosmic radiation. For several years since the first spacecraft flyby over the planet, it was believed that some lifeform lived on the planet, producing these hydrocarbons. Several missions were sent to the planet, most of them actually landed, but no biological component was found. Today there have been only one manned mission to the planet, which installed a research station on it; it was the first mission sent by the Community of Nations from Hiwashazu. This planet also had a research station operated by means of artificial intelligence, the first sent by the RIES.

6. SIXTH PLANET

Mass: 5.32 x 10^24 kg (0.9 Earth)

Average density: 3.2g/cm³

Diameter: 14,690 km

Composition: 32.4% water, 29.9% nitrogen, 27.9% carbon dioxide, 9.8% other elements

Gravity: 6.58m/s, 0.67G

Rotational period: 2.2 Earth days

Orbital Period: 24.47 Earth years

Semimajor axis: 1,259 million km (8.4 AU)

Eccentricity: 0.0352 (1,214 mi km periastron, 1,303 mi km apastron)

Rotational tilt: 29.4°

Albedo: 0.66

Atmosphere: virtually nonexistent (mainly helium, nitrogen, hydrogen and oxygen)

Temperatures: 75K (-198°C/-324°F), minimal variation

Moons: 8 (small, asteroid-sized), icy ring system

This planet is so far away from its parent star that it has virtually no atmosphere due to its low temperatures. Most of the planet's chemical components are in the form of compounds with "high" melting points, and a very thin atmosphere forms when stellar radiation reaches the planet and breaks down the components on the surface. This breakdown by radiation leaves free carbon atoms, that quickly react with other surface components, creating new hydrocarbons; these hydrocarbons then are driven inwards to the planet by a tecnonics-like mechanism that occur on the planet. Although it is an icy planet, it is believed that in its interior the temperatures might be a little higher than on the surface, and the ice core interacts with the planet's crust in a similar fashion, albeit slower, to the one seen on rocky planets.

This planet has 8 small moons, all probably captured asteroids. The planet's ring system orbits the planet from east to west and not west to east as all the other bodies in the system; it was probably a captured comet nucleus that came too close and was broken apart.

THIRA'S WORMHOLE

Just like every other wormhole in the network, this has 251.95 meters in diameter and 14,204 Earth mass. It orbits the parent star around 1209 AU away from the star, and takes 41,574 Earth years to complete one orbit. The gravitational pull of the wormhole is clearing its orbit from cometary nuclei; by analysing the "shadow" left behind by the wormhole, it's been estimated that it was placed there around 10 to 12 thousand Earth years ago. The other side of the wormhole ends in the Milky Way Wormhole Complex just like Solar System's and Captors System's wormholes.