11-16-2025, 09:50 PM
⭐ THREAD 3 — Super-Earths, Mini-Neptunes & Rogue Worlds
The Wild Zoo of Exoplanets
Exoplanets & Habitability Series — The Lumin Archive
? Exoplanets Come in Types We Never Imagined
For most of human history, we thought all planets were like the ones in our Solar System:
• rocky inner worlds
• gas giants further out
• maybe a few moons
Then the Kepler Space Telescope changed everything.
We now know the universe is filled with planet types that do not exist here —
stranger, wilder, more extreme worlds than anything in science fiction.
This thread explores the most common — and the most surprising.
1️⃣ Super-Earths — The Universe’s Favourite Planet
Super-Earths are planets:
• 1.5–2× Earth’s radius
• 2–10× Earth’s mass
• common everywhere
• completely absent in our Solar System
Some may be:
• ocean worlds
• volcanic worlds
• mega-plate-tectonic worlds
• mini-Earths with thick atmospheres
Habitability potential: HIGH.
These are some of the best candidates for life.
2️⃣ Mini-Neptunes — The Most Common of All
Mini-Neptunes are halfway between:
• a rocky planet
• a gas giant
They often have:
• thick hydrogen atmospheres
• deep liquid layers
• possible high-pressure oceans
They may hide a rocky core — but reaching that core might be impossible for life.
Habitability potential: LOW–MEDIUM
(but still possible, depending on atmosphere loss).
3️⃣ Hot Jupiters — The Impossible Planets
Gas giants orbiting insanely close to their star:
• years that last 1–4 days
• surface temperatures above 1,500°C
• wild atmospheric winds
• evaporating atmospheres
• tidal locking
These planets shouldn’t exist — but they do.
Habitability: ZERO.
But they are incredibly useful for science because they are easy to study.
4️⃣ Lava Worlds — Oceans of Molten Rock
Extreme heat + close orbits = worlds like:
55 Cancri e
K2-141b
These planets have:
• lava oceans
• rock-vapour atmospheres
• raining molten minerals
• supersonic rock winds
Habitability: ZERO — but scientifically fascinating.
5️⃣ Ocean Worlds — Planets Covered in Global Seas
Imagine a planet with:
• no continents
• 100 km deep oceans
• high-pressure ice layers
• possible hydrothermal vents
These may be some of the BEST candidates for life —
especially simple or microbial life.
Habitability: HIGH (for non-land life).
6️⃣ Ice Giants & Sub-Neptunes
Similar to Uranus or Neptune but smaller.
Some may have:
• ammonia oceans
• deep water layers
• thick clouds
• exotic weather cycles
Potential for life is uncertain but not zero.
7️⃣ Rogue Planets — Worlds Without a Star
Drifting alone in the darkness.
No sunlight.
No orbit.
No heat from a star.
But…
If the planet is massive enough, internal heating could support:
• subsurface oceans
• geothermal vents
• entire ecosystems beneath ice
Meaning…
A star is not required for life.
Rogue planets might host hidden oceans warmed from within.
8️⃣ Hycean Worlds — A New Class That Might Host Life
Introduced recently, these are:
• mini-Neptunes
• with deep oceans
• under thick hydrogen atmospheres
• warm, stable, and surprisingly pleasant beneath the clouds
Hycean worlds could be some of the easiest planets for life to evolve.
We may detect biosignatures on these FIRST.
? Why This Matters for Habitability
With all these planet types, it becomes clear:
Habitability is not rare — it is diverse.
Life might exist on:
• Earth-like surfaces
• deep oceans
• hydrogen atmospheres
• subsurface seas
• geothermal pockets
• rogue worlds
The universe is more creative than we ever imagined.
Written by LeeJohnston & Liora
The Lumin Archive Research Division
The Wild Zoo of Exoplanets
Exoplanets & Habitability Series — The Lumin Archive
? Exoplanets Come in Types We Never Imagined
For most of human history, we thought all planets were like the ones in our Solar System:
• rocky inner worlds
• gas giants further out
• maybe a few moons
Then the Kepler Space Telescope changed everything.
We now know the universe is filled with planet types that do not exist here —
stranger, wilder, more extreme worlds than anything in science fiction.
This thread explores the most common — and the most surprising.
1️⃣ Super-Earths — The Universe’s Favourite Planet
Super-Earths are planets:
• 1.5–2× Earth’s radius
• 2–10× Earth’s mass
• common everywhere
• completely absent in our Solar System
Some may be:
• ocean worlds
• volcanic worlds
• mega-plate-tectonic worlds
• mini-Earths with thick atmospheres
Habitability potential: HIGH.
These are some of the best candidates for life.
2️⃣ Mini-Neptunes — The Most Common of All
Mini-Neptunes are halfway between:
• a rocky planet
• a gas giant
They often have:
• thick hydrogen atmospheres
• deep liquid layers
• possible high-pressure oceans
They may hide a rocky core — but reaching that core might be impossible for life.
Habitability potential: LOW–MEDIUM
(but still possible, depending on atmosphere loss).
3️⃣ Hot Jupiters — The Impossible Planets
Gas giants orbiting insanely close to their star:
• years that last 1–4 days
• surface temperatures above 1,500°C
• wild atmospheric winds
• evaporating atmospheres
• tidal locking
These planets shouldn’t exist — but they do.
Habitability: ZERO.
But they are incredibly useful for science because they are easy to study.
4️⃣ Lava Worlds — Oceans of Molten Rock
Extreme heat + close orbits = worlds like:
55 Cancri e
K2-141b
These planets have:
• lava oceans
• rock-vapour atmospheres
• raining molten minerals
• supersonic rock winds
Habitability: ZERO — but scientifically fascinating.
5️⃣ Ocean Worlds — Planets Covered in Global Seas
Imagine a planet with:
• no continents
• 100 km deep oceans
• high-pressure ice layers
• possible hydrothermal vents
These may be some of the BEST candidates for life —
especially simple or microbial life.
Habitability: HIGH (for non-land life).
6️⃣ Ice Giants & Sub-Neptunes
Similar to Uranus or Neptune but smaller.
Some may have:
• ammonia oceans
• deep water layers
• thick clouds
• exotic weather cycles
Potential for life is uncertain but not zero.
7️⃣ Rogue Planets — Worlds Without a Star
Drifting alone in the darkness.
No sunlight.
No orbit.
No heat from a star.
But…
If the planet is massive enough, internal heating could support:
• subsurface oceans
• geothermal vents
• entire ecosystems beneath ice
Meaning…
A star is not required for life.
Rogue planets might host hidden oceans warmed from within.
8️⃣ Hycean Worlds — A New Class That Might Host Life
Introduced recently, these are:
• mini-Neptunes
• with deep oceans
• under thick hydrogen atmospheres
• warm, stable, and surprisingly pleasant beneath the clouds
Hycean worlds could be some of the easiest planets for life to evolve.
We may detect biosignatures on these FIRST.
? Why This Matters for Habitability
With all these planet types, it becomes clear:
Habitability is not rare — it is diverse.
Life might exist on:
• Earth-like surfaces
• deep oceans
• hydrogen atmospheres
• subsurface seas
• geothermal pockets
• rogue worlds
The universe is more creative than we ever imagined.
Written by LeeJohnston & Liora
The Lumin Archive Research Division