Themisto

Themisto is a fascinating moon in our Solar System that has captured the attention of astronomers and space enthusiasts alike. With a Themisto radius of 4 km, making it 1592.8× smaller than Earth's size, this celestial body presents unique characteristics that distinguish it from other objects in our cosmic neighborhood. Positioned at an average distance of 7.51e+6 km (0.050 AU) from the Sun, Themisto occupies a significant place in the Solar System's architecture. As a moon, Themisto demonstrates the incredible diversity of natural satellites that orbit larger celestial bodies throughout our Solar System.

The Themisto physical characteristics reveal a world of remarkable dimensions and properties. The Themisto radius measures 4 km, making it 1592.8× smaller than Earth's size. The Themisto mass of 6.90e+14 kg represents 8655072463.8× smaller than Earth's mass, giving this world substantial gravitational influence. The Themisto density of 1 g/cm³ (5.5× smaller than Earth's density) provides clues about its internal composition, while the surface gravity of 0.003 m/s² (3382.8× smaller than Earth's gravity) determines how objects behave on its surface. The low density indicates a composition dominated by lighter elements, characteristic of gas giants or icy bodies.

The Themisto orbit reveals fascinating details about its journey around the Sun and its relationship to other Solar System objects. The Themisto orbit has a semimajor axis of 7.51e+6 km (0.050 AU), placing it 19.9× smaller than Earth's distance from the Sun. At its closest approach (perihelion), Themisto comes within 5.91e+6 km of the Sun, while at its farthest point (aphelion), it reaches 8.87e+6 km, creating a 39.5% variation in solar distance. The Themisto orbit is moderately elliptical with an eccentricity of 0.242 (14.5× Earth's orbital eccentricity), creating noticeable seasonal variations in solar radiation. The Themisto orbit takes 0.04 hours to complete (242717.7× smaller than Earth's orbital period), defining the length of its year. The orbital inclination of 43.08° indicates how much the Themisto orbit is tilted relative to the Solar System's ecliptic plane. This high inclination suggests Themisto may have experienced significant gravitational perturbations or formed in a different region of the Solar System.

The Themisto rotation and axial orientation provide crucial insights into its daily and seasonal cycles, as well as its orbital dynamics. The Themisto axial tilt of 0° determines the intensity and nature of seasonal variations. With minimal axial tilt, Themisto experiences virtually no seasonal changes, maintaining relatively constant temperatures throughout its year. The orbital orientation parameters reveal additional details about Themisto's position in space. The mean anomaly of 0° indicates the planet's current position in its orbit relative to its perihelion. The argument of periapsis of 0° shows how the orbit's orientation changes over time due to gravitational perturbations. The longitude of ascending node of 0° defines the reference point where the orbit crosses the ecliptic plane.

The Themisto temperature and atmospheric conditions are fundamental to understanding its habitability and environmental characteristics. The Themisto average temperature of 0.0 K (-273.1 °C) (-459.7°F) provides the baseline for understanding its climate. These extremely cold temperatures make Themisto inhospitable to life as we know it, with any atmosphere likely frozen solid on the surface. Compared to Earth's average temperature of 15°C (59°F), Themisto presents a dramatically different thermal environment. Being closer to the Sun than Earth, Themisto receives more intense solar radiation, contributing to its temperature profile. The elliptical orbit creates significant temperature variations throughout the year, with extreme seasonal changes.

The Themisto escape velocity and shape characteristics reveal important details about its gravitational field and rotational dynamics. The Themisto escape velocity of 0 m/s determines how easily objects can break free from its gravitational pull. This relatively low escape velocity means that gases and light molecules can easily escape into space, making it difficult for Themisto to retain a substantial atmosphere. The Themisto flattening of 0.0000% indicates how much the planet's rotation affects its shape. This minimal flattening suggests a nearly spherical shape, indicating either slow rotation or a very rigid internal structure.