09 December, 2022

SCIENCE&ARTWORK | THE HOKU | ASTROPHYSICS | PART 1

SYSTEM OVERVIEW



PAZA, the Greater Sister

G8V yellow dwarf star

Temperature 5435 K

(in solar units)

Mass 0.88

Luminosity 0.64

Radius 0.90

Metallicity Z* ~0.832 [Fe/H]


Abs. Magnitude +5.32

Rotational period 38 days


Unenja, the Little Sister

M4V red dwarf star

Temperature 3220 K

(in solar units)

Mass 0.124

Luminosity 0.004 ± 0.001 (weakly variable)

Radius 0.188

Metallicity Z* ~1.122 [Fe/H]


Abs. Magnitude +10.77 ± 0.19

Soft-flaring BY Draconis variable star, flare period is the same as rotational period of 52 days.


Orbital separation 0.15 AU or 22.4 million km on average.

Orbital eccentricity 0.271

Orbital period ~21 Earth-days or 16 Hoku-days


Total mass of the system amounts to roughly one solar mass, making orbital period calculations easier.



SYSTEM ZONES

Debris belt between 0.42 ~ 0.50 AU

Venus zone 0.68 AU

Water-loss 0.76 AU

Mean HZ 0.80 AU

True HZ 0.81 AU

Cold HZ 1.41 AU

Frost line 1.55 AU

Asteroid belt between 2.0 ~ 3.0 AU

Kuiper distance 32.20 AU


PLANETS

The planets of the system are named after the gods of an ancient civilization of theirs, pretty much like we call our planets by their Roman names (except you, Uranus).

In order from their star:



Bagede // BGD

The fast trickster, joker.

Hot-Neptune, ~116°C

Mass 20.95 Earth-masses

Radius 6.43 Earth-radii (thermally expanded)

Semi-major axis 0.33 AU

Orbital eccentricity 0.211

Orbital period 69 Earth-days (nice!) or 52.4 Hoku-days


Bagede’s orbit is quite anomalous given the system’s distribution of mass, no planets could form this close to the binary pair, the atmospheric escape rate does indicate it to have formed much further away from the binary, being flung into a tight eccentric and inclined orbit in the system’s deep past.



Ovilgeza // OVGZ

God of lightning, fire, archery, and messengers.

Hot-Neptune, ~18°C

Mass 24.54 Earth-masses

Radius 6.74 Earth-radii (thermally expanded)

Semi-major axis 0.59 AU

Orbital eccentricity 0.024

Orbital period 168 Earth-days, or 127.4 Hoku-days


Ovilgeza is one planet believed to have been quite disturbed by the migration of Bagede, with a tighter orbit than what its size would indicate, this can be said because the both ends of the debris belt around the binary pair are missing, with the missing mass being distributed to the two inner planets.



Auot’zae // AUTZAE

Orb of the World, the Earth.

Tropical Superterran, ~17°C

Mass 2.54 Earth-masses

Radius 1.42 Earth-radii

Semi-major axis 0.80 AU

Orbital eccentricity 0.014

Orbital period 263.3 Earth-days, or 200 Hoku-days


Has a small moon with half the mass of Luna.


Informally known as Hokushoku (the Hoku World, in the classical language) throughout the Dominion, it is the only planet in the system naturally capable of hosting Life as we know it, it is the homeworld of the Hoku. On the surface it is pretty similar to Earth, both in gravitational acceleration and landscape-wise, the planet was once covered in lush bright-yellow vegetation which nowadays struggle to get a foothold, due the destruction of the ozone layer by a hostile force. The planet has one small moon, but due the closer distance it creates tides stronger than Earth’s moon.



Namenza // NAMZ

Goddess of spring, harvest, and life.

Icy Superterran, on average -44°C

Mass 3.55 Earth-masses

Radius 1.70 Earth-radii

Semi-major axis 1.21 AU

Orbital eccentricity 0.019

Orbital period 1y120d, or 1Hy92Hd


Namenza is a bright icy world, its nitrogen and carbon dioxide atmosphere is just thick enough to maintain some levels of liquid water on the surface of the planet. However, despite the friendly conditions for life, it is completely sterile. It happens to be that the amount of volatiles in the planet's upper layers cannot generate enough pressure for efficient plate tectonics, thus the surface is pretty stagnant of chemical recycling. The crawling slow increase in Paza’s luminosity is also blamed to have kept this planet way too long in the dark to feed the chemical processes leading to the genesis of life, and now the planet is an icy wasteland, much contrary to the goddess it was named after.


ASTEROID BELT

2.0 ~ 3.0 AU

Some 3.2% of the Moon’s mass



Kotishera // KTXER

Goddess of arts, crafts, hunt, and war.

Gas Giant, ~ -150°C

Mass 165 Earth-masses

Radius 9.17 Earth-radii

Semi-major axis 3.60 AU

Orbital eccentricity 0.047

Orbital period 6y303d, or 9Hy96Hd


Kotishera can be said to be a Saturn-like gas giant, very light and sporting a thin ring reminiscent of a recently minced icy moon. It has many other icy moons to spare.



Udeqera // UDQR

Goddess of the underworld and the furies.

Gas Giant, ~ -190°C

Mass 1442 Earth-masses or 4.53 Jupiter-masses

Radius 12.83 Earth-radii

Semi-major axis 6.80 AU

Orbital eccentricity 0.035

Orbital period 17y266d, or 24Hy120Hd


Udeqera is a heavy jovian planet, with over four-times the mass of Jupiter, this giant holds a vast collection of moons named after the furies, and a very solid ring system. The total mass of the moon system is roughly ¼ of the Earth’s mass, half of which is concentrated in its three major moons. It is the last planet in the system which can be seen to the naked-eye.



Koshazat // KXZT

Titan of time, heavens, and weather.

Ice Giant, ~ -215°C

Mass 17.44 Earth-masses

Radius 6.56 Earth-radii

Semi-major axis 13.23 AU

Orbital eccentricity 0.010

Orbital period 47y350d, or 66Hy106Hd


The only planet not named after a main god of the classical pantheon, that happens because it was only discovered after the invention of the telescope. The only major entity missing from the sky was the titan of Time itself, and name was promptly accepted.


There are no major planets beyond this point, but a handful of dwarf planets and a myriad of comets in a debris belt called The Underworld, in classic Hoku.



-M.O. Valent, 05/12/2022

-M.O. Valent, posted 09/12/2022

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