Science // Planetary systems

Solar system types and the orrery

Every star in Pax Abyssi has a planetary system, laid out from one of 23 templates taken from what exoplanet surveys have found: packed red dwarf families, hot Jupiters, giants far out, planets around both stars of a binary, and systems like our own. The orrery charts each one at any date, with the physics drawn over it.

In Pax Abyssi: Sol in the orrery, with the habitable zone, the frost and soot lines and the tidal lock radius labelled, the main belt, the Kuiper belt and the Trojan clusters marked, and the edge-on strip below.

In-game capture, pre-alpha, orrery

01 // What a system is

A star, its companions, and everything bound to them

In the gameevery catalogue star

In Pax Abyssi a planetary system is the star, any companion stars, and the planets, moons, belts and Trojan clusters that orbit them. Every star in the galaxy has one, and the same star always gives the same system.

One generator builds every system. Around the stars astronomers have catalogued it runs ahead of time, so the systems are there when you arrive; around the stars the simulation generates to fill the rest of the Milky Way it runs the moment you pick the star. Seeded by the star, it gives the same answer every time.

Where astronomers have found planets, the system keeps them and is built around them. Everywhere else the planets are the simulation's own, drawn from what the exoplanet surveys say is common for a star of that kind. The layout comes first, and it is chosen from 23 templates, each one a pattern the surveys have found again and again: tight families of small worlds, chains locked in resonance, lone hot giants, giants far out, planets around both stars of a binary, and systems laid out like our own.

1
The star
Mass, radius, temperature and age from the catalogue row and the published relations for its spectral type, and any companion star with its orbit.
2
Planets or none
One probability, read off the star's type: 0.89 for a G2 dwarf like the Sun, 0.96 for red dwarfs, 0.57 for an A0 star, 0.10 for a B0. A close companion, low metallicity or an evolved star lowers it.
3
The template
One of 23 layouts, drawn from weights set by the star's class and then adjusted for its metallicity, age, companions and place in the Galaxy.
4
The orbits
Each template lays out its orbital slots by its own rule: resonant period ratios, a geometric factor, or the frost line as the divide.
5
The worlds
Every slot is filled with a planet type from its temperature and the material the disc held there, then moons, rings, belts and Trojan clusters.

Catalogue systems: 6,559; one for every catalogue star with a system sheetSim
With planets: 3,235; half of them; the bright sky is full of hot and evolved starsSim
Planets: 13,653; in the catalogue systems aloneSim
Templates: 23; planet-bearing layouts, and the empty systemSim

In the wikiStar system generation Planet occurrence Sol

02 // How common each kind is

What the generator built around the catalogue stars

Every generated system records the template it came from. These are the counts across the 3,235 catalogue systems that have planets.

Special layouts

30.4%

983 systems

Dusty systems with few planets, lone temperate worlds, planets around both stars of a pair, and the general log-spaced and scattered layouts.

Sol-like and resonant

24.6%

796 systems

Rocky worlds inside the frost line and giants beyond it, geometric spacing, and chains locked in resonance.

Compact

23.7%

768 systems

Several small planets packed close to the star, most of them inside the distance of Mercury's orbit.

Wide and outer

14.1%

455 systems

Planets far from the star: giants beyond 10 AU, belts of ice giants, and single distant worlds.

Giant-dominated

8.4%

273 systems

A giant close to the star, a hot Neptune, or a pair of giants in resonance setting the layout.

The 23 templatescatalogue systems with planets

Sim

The 23 templates
Template	What it builds	Systems	Share
Debris-dominatedSpecial layouts	A few survivors with wide gaps where dusty belts lie	317	9.8%
Compact mixedCompact	A tight system of rocky worlds and sub-Neptunes	314	9.7%
Log-uniformSpecial layouts	Orbits evenly spaced in the logarithm of distance	265	8.2%
Compact rockyCompact	Four to seven rocky planets packed close, linked by resonances	254	7.9%
Geometric spacingSol-like and resonant	Each orbit a near-constant factor beyond the last	225	7.0%
Single outer planetWide and outer	One or two distant planets	216	6.7%
Resonant chain, similar planetsSol-like and resonant	A resonant chain of look-alike planets	187	5.8%
Resonant chain, mixed planetsSol-like and resonant	A resonant chain of varied planets	157	4.9%
CircumbinarySpecial layouts	Planets orbiting both stars of a close pair	151	4.7%
Lone temperate planetSpecial layouts	A single planet at a temperate distance	135	4.2%
Sub-Neptune chainCompact	Similar sub-Neptunes with period ratios of 1.5 to 3	133	4.1%
Sol-likeSol-like and resonant	Rocky planets inside the frost line, giants beyond it	124	3.8%
Random spacingSpecial layouts	No pattern, as after planets scatter one another	115	3.6%
Mixed architectureSol-like and resonant	Two patterns in one system, inner and outer	103	3.2%
Giant pairGiant-dominated	Two giants in or near resonance, with smaller company	101	3.1%
Wide giantsWide and outer	Giants beyond about 10 AU	81	2.5%
Ice giant beltWide and outer	Several Neptune-mass planets spread through the system	78	2.4%
Warm JupiterGiant-dominated	A giant at 0.1 to 0.5 AU with close companions	71	2.2%
Hot JupiterGiant-dominated	A giant close to the star, one to three distant companions	69	2.1%
Ultra-compactCompact	A packed system starting a few hundredths of an AU out	67	2.1%
Very wideWide and outer	Planets only beyond the carbon monoxide snow line	44	1.4%
HierarchicalWide and outer	Groups of planets at very different scales	36	1.1%
Hot NeptuneGiant-dominated	A close-in Neptune-sized planet with companions	32	1.0%

The commonest layout in the catalogue sky is the debris-dominated system, a few planets with dusty belts in the gaps, at 9.7 per cent. That reflects the sky as much as the generator: the stars bright enough to see are disproportionately hot A and B stars, giants and binaries, and those draw dusty, wide and sparse layouts. Half of the 6,559 catalogue systems have no planets at all, for the same reason.

Across the rest of the Milky Way, which the simulation fills to its true population of 111 billion stars, red dwarfs are the majority, as they are in the real Galaxy, and their compact families of small planets become the commonest systems there are. The starting weights by star class encode the survey trends:

Red dwarf (M)
Compact rocky 20.5%, compact mixed 14.8%, resonant chain 12.3%
Small planets packed close, as Kepler and TRAPPIST-1 show
Sun-like (G)
Geometric, log-uniform and compact mixed at 9.9% each
The most even spread; the Sol-like template starts at 2%
Hot white (A)
Debris-dominated 27.4%, single outer planet 13.7%
Few small close-in planets around hot stars; dusty discs and wide giants

Metal-rich stars have their giant-bearing templates weighted up and old, metal-poor stars have them weighted down; evolved stars lose the close-in layouts, and a companion star removes the templates whose orbits it would not allow.

In the wikiPlanetary system archetypes Planet occurrence Red dwarf

Red dwarfs and their planets

03 // Nine systems

One system for each kind of layout

Real catalogue stars, charted in the game's orrery. Where astronomers have found planets they are kept; the rest are generated. Each picture is the whole system fitted to the screen, with the habitable zone, the frost and soot lines and the star's card open.

The in-game orrery on Gliese 892: nine planet orbits, the dashed habitable zone and frost line, two giants beyond the frost line, the star's card open on the right — In Pax Abyssi: Gliese 892 in the orrery, small worlds packed inside the habitable zone and the giants beyond the frost line.
In-game capture, pre-alpha, orrery

Sol-like and resonant // Sol-like // 124 systems

Gliese 892: rock inside the frost line, giants outside it

An orange dwarf 6.5 parsecs away, with under a third of the Sun's light. Six small worlds crowd inside 0.4 AU: volcanic super-Earths, a young desert and two mini-Neptunes. The frost line sits at 1.48 AU, and the first giant forms just beyond it at 1.63 AU, a second at 3.1 AU, with an ice world out at 6.3 AU. This is the rule the Solar System follows, and around a G star the generator starts it at a weight of only 2 per cent, because surveys find layouts like ours uncommon.

Planetary system archetypes

Open in the web orrery

The in-game orrery on 89 Leonis: eight evenly widening orbits around a yellow-white star, the habitable zone and frost line dashed — In Pax Abyssi: 89 Leonis, eight planets on orbits that widen by a near-constant factor.
In-game capture, pre-alpha, orrery

Sol-like and resonant // Geometric spacing // 225 systems

89 Leonis: every orbit half again the last

Eight planets from 0.30 to 5.2 AU, each orbit about one and a half times wider than the one inside it. The ratio comes from the star's mass, 1.4 plus 0.3 times the logarithm of the mass in suns plus 0.1, which gives 1.41 for the Sun, varied by up to 10 per cent planet to planet. Most known systems of four or more planets follow a spacing law of this kind more closely than the Solar System does.

Orbit

Open in the web orrery

Compact // Sub-Neptune chain // 133 systems

Gliese 690.1: a red dwarf's whole family inside 0.16 AU

A red dwarf with a hundredth of the Sun's light. Its habitable zone runs from 0.078 to 0.206 AU and its frost line is at 0.26 AU, so the four planets sit closer to their star than Mercury does to ours. Three mini-Neptunes lead, and the fourth, a deep-ocean super-Earth at 0.155 AU, orbits inside the habitable zone. For red dwarfs the generator weights the compact and resonant templates highest, compact rocky alone at about a fifth of the pool, after systems like TRAPPIST-1.

Red dwarf Mini-Neptune

Open in the web orrery

The in-game orrery on Nu2 Lupi: seven orbits around a yellow star, the three inner planets measured and four generated beyond them — In Pax Abyssi: Nu2 Lupi, its three known planets inside half an AU and the generated chain beyond them.
In-game capture, pre-alpha, orrery

Compact // Sub-Neptune chain // 133 systems

Nu2 Lupi: three measured planets, and the rest of the chain

A Sun-like star 14.8 parsecs away with three planets astronomers have found: a super-Earth and two sub-Neptunes at 0.096, 0.17 and 0.43 AU, of 4.7, 11.2 and 8.8 Earth masses. A star with catalogued planets keeps them, and the generator gives it the template that best fits them, here a chain of similar sub-Neptunes. It then fills the gaps: four more planets continue the chain out to 2.2 AU.

Super-Earth Planet occurrence

Open in the web orrery

The in-game orrery on 49 Librae: a hot giant hugging the star at the centre, then wide empty space out to a barren rock, an ice world and a cold giant — In Pax Abyssi: 49 Librae, a hot giant close to the star and three distant companions.
In-game capture, pre-alpha, orrery

Giant-dominated // Hot Jupiter // 69 systems

49 Librae: a hot giant with nothing beside it

A giant of about five Jupiter masses orbits 0.097 AU from this yellow-white star at 1,550 K. Nothing else lies within 2.6 AU of it: a barren rock follows at 2.7 AU, an ice world at 7.0 AU and a cold giant at 10.5 AU. That is the pattern Kepler found, hot Jupiters without close neighbours, and the companions farther out match the radial-velocity surveys, which find a massive outer companion in about half of hot-Jupiter systems.

Hot Jupiter

The in-game orrery on Gliese 279: two rocky worlds close in, a pair of giants at 0.77 and 1.6 AU, and two outer planets — In Pax Abyssi: Gliese 279, a resonant pair of giants on the warm side of the habitable zone.
In-game capture, pre-alpha, orrery

Giant-dominated // Giant pair // 101 systems

Gliese 279: two giants locked near three to one

Two temperate giants at 0.77 and 1.6 AU have orbital periods close to a three to one ratio. The template is modelled on Jupiter and Saturn, whose periods sit near five to two. Two barren rocks sit inside them, a third giant at 7.0 AU and a carbon planet at 11.2 AU outside them.

Gas giant

Open in the web orrery

The in-game orrery on 24 Ophiuchi: two stars turning about their barycentre at the centre, four planets on wide orbits around the pair — In Pax Abyssi: 24 Ophiuchi, a circumbinary system charted about the barycentre of its two stars.
In-game capture, pre-alpha, orrery

Special layouts // Circumbinary // 151 systems

24 Ophiuchi: planets around both stars

Two hot stars 0.78 AU apart, with four planets circling the pair: a hot ice giant at 3.9 AU, mini-Neptunes at 10.5 and 36 AU and an ice world at 132 AU. The innermost orbit is five times the stars' separation, outside the two to four times that orbital integrations allow for a planet around a binary. The orrery centres a circumbinary system on the pair's barycentre and draws both stars turning about it.

Orbit

Open in the web orrery

Special layouts // Debris-dominated // 317 systems, the commonest

Pi Cassiopeiae: two belts and the planets between

A white A star with four planets and two belts of debris, the inner from 9.1 to 14.5 AU and the outer from 30 to 36 AU. A cold brine world orbits at 6.2 AU, inside the habitable zone, and a cold giant at 23 AU sits in the gap between the belts. A dim red companion swings far outside on a long dashed orbit. Hot stars draw this template most, more than a quarter of the pool for an A star, after the dusty discs found around Vega and Fomalhaut.

Asteroid belt

Open in the web orrery

The in-game orrery on Gliese 785: five orbits around an orange star, three of them ice giants, with an outer belt — In Pax Abyssi: Gliese 785, its two known Neptune-mass planets and a third ice giant farther out.
In-game capture, pre-alpha, orrery

Wide and outer // Ice giant belt // 78 systems

Gliese 785: a system of Neptunes

An orange dwarf 8.9 parsecs away. Astronomers have found two Neptune-mass planets here, at 0.32 and 1.18 AU, and the generator keeps them and builds the system around them: a third ice giant at 3.9 AU, a molten super-Earth close in, a frozen super-Earth at 2.5 AU and an outer belt from 5.1 to 6.2 AU.

Ice giant

Open in the web orrery

04 // What the orrery charts

Every system solved for the date you are flying

In the gamein-game and on this site

Press O in the game and the orrery opens over a paused world: the system you are in, or the star you picked on the galaxy map, seen from above its north pole, every planet and moon on its own orbit at a date you can run forwards or back.

The in-game orrery on Sol with a Hohmann transfer from Earth to Mars drawn as an arc, Earth's L3, L4 and L5 points marked, and a panel listing departure and arrival burns, transfer time and the launch window — In Pax Abyssi: an Earth to Mars Hohmann transfer plotted in the orrery, with the burns, the 259-day transfer, the launch window and Earth's Lagrange points.
In-game capture, pre-alpha, orrery

Orbits use J2000 elements and a Kepler solve, so a planet is where its orbit puts it on the date shown, and the chart can run from one second a second to years a second. The orrery is drawn fresh every frame from the same system sheet the game flies, and its side panel is the galaxy map's, so the two screens never disagree.

Pick two planets and it plots a Hohmann transfer, the cheapest two-burn path between circular orbits, then follows the planets and counts down to the launch window. Earth to Mars takes 2.95 kilometres a second to leave and 2.65 to arrive, 259 days in transit, with Mars 44 degrees ahead of Earth at departure. Set a body as your nav target and the orrery becomes the chart you fly by.

Open Sol in the web orrery Pick a star on the galaxy map

Habitable zone

Where liquid water can stand on a surface. It scales with the square root of the star's luminosity: 0.95 to 1.37 AU for the Sun, a tenth or two of an AU for a dim red dwarf.

Frost line

Beyond it water froze out of the young disc and the solids roughly quadrupled, which is why giants form outside it. 2.7 AU for the Sun.

Soot and melt lines

Inside the soot line carbon burned off the dust and worlds formed dry; inside the melt line bare rock melts.

Tidal lock radius

Inside it a world turns one face to its star for good, the rule for most planets of a red dwarf.

Hill spheres

How far a planet's gravity holds a moon, and in the game where your ship's frame changes from the star's to the planet's.

Bow shocks

Where each planet's magnetic field turns the stellar wind, nose to the star.

Binaries

A companion star on its own orbit, the barycentre the pair turns about, Roche lobes and exact Lagrange points; a circumbinary system is centred on the barycentre.