Pronunciation //
Alternative names Augarnir, Aeduca
Adjective Therosian
Orbital characteristics
Periapsis 183,442,892 km
Apoapsis 199,527,656 km
Mean orbit radius 191,485,274 km
Eccentricity 0.042
Orbital period 504.045 Earth days
Inclination 0.1
Known satellites Chiron
Physical characteristics
Mean radius 7,373 km
Flattening 0.003
Circumference 46,326 km
Surface area 170,693,945 km
Volume 1.679 * 10^18
Mass 9.26 * 10^24 kg
Mean density 5.52 g/cm3
Equatorial surface gravity 1.15 G
Sidereal rotation period 26 hours
Axial tilt 23 degrees
Albedo 30
Surface temp. min mean max
Celsius 12°C
Fahrenheit 54°F
Surface pressure 105 kilopascals

Theros is the fourth planet orbiting the star Haelos. It is the middle of three life-bearing worlds within the inner solar system, the others being Elrune and Aloris. It is the most similar planet in the Haelos system to Earth. Unique to Theros among the other life-bearing planets is the sheer amount of sophonts that have evolved on the planet. There are sixteen species of sophonts currently known to inhabit the planet.

Names and Etymology

Physical Characteristics

Theros is a rocky terrestrial planet. Of the five inner planets, it has the highest size and mass while having the highest density and surface gravity of the five.

Orbital Characteristics


As one of three habitable planets in the inner solar system, Theros stands out as having the most biological diversity as evident by its sixteen sophont species that currently inhabit the planet.


Theros formed around 4.6 billion Earth years ago by accretion.


Chiron is the only moon of Theros.