Titan (moon)Titan is the largest moon of Saturn and the second largest in the Solar System. It is the only moon that is known to have a dense atmosphere (denser than that of Earth), and is the only known object in the Solar System besides Earth with clear evidence of stable bodies of surface liquid. Titan is one of seven gravitationally rounded moons of Saturn, and is the second-most distant among them.
Ganymede (moon)Apparent magnitude4.61 (opposition)4.38 (in 1951)Angular diameter1.2 to 1.8 arcsecondsAtmosphereSurface pressure0.2–1.2 μPa (1.97×10–1.18×10 atm)Composition by volumemostly oxygenGanymede is a natural satellite of Jupiter and is the largest and most massive moon in the Solar System.
Natural satelliteAstronomical body that orbits a planetThe Moon orbiting around Earth (observed by the Deep Space Climate Observatory)A natural satellite is, in the most common usage, an astronomical body that orbits a planet, dwarf planet, or small Solar System body (or sometimes another natural satellite). Natural satellites are colloquially referred to as moons, by analogy with the Moon, Earth's natural satellite.
Irregular moonIn astronomy, an irregular moon, irregular satellite, or irregular natural satellite is a natural satellite following an orbit that is irregular in some or all of the following ways: distant; inclined; highly elliptical; retrograde. They have often been captured from elsewhere by their parent planet, unlike regular satellites that formed in orbit around them.
AtmosphereAn atmosphere is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. The name originates from Ancient Greek (atmós)'vapour, steam' and (sphaîra)'sphere'. An object acquires most of its atmosphere during its primordial epoch, either by accretion of matter or by outgassing of volatiles.
Mercury (planet)Mercury is the first planet from the Sun and the smallest in the Solar System. It is a rocky planet with a trace atmosphere and a surface gravity slightly lower than that of Mars. The surface of Mercury is similar to Earth's Moon, being cratered, with an expansive rupes system generated from thrust faults, and bright ray systems, formed by ejecta.
List of gravitationally rounded objects of the Solar SystemThis is a list of most likely gravitationally rounded objects (GRO) of the Solar System, which are objects that have a rounded, ellipsoidal shape due to their own gravity (but are not necessarily in hydrostatic equilibrium). Apart from the Sun itself, these objects qualify as planets according to common geophysical definitions of that term.
Giant-impact hypothesisThe giant-impact hypothesis, sometimes called the Theia Impact, is an astrogeology hypothesis for the formation of the Moon first proposed in 1946 by Canadian geologist Reginald Daly.
AsteroidAn asteroid is a minor planet—an object larger than a meteoroid (thus 1 meter or larger) that is neither a planet nor an identified comet—that orbits within the inner Solar System or is co-orbital with Jupiter (Trojan asteroids). Asteroids are rocky, metallic, or icy bodies with no atmosphere, and are broadly classified into C-type (carbonaceous), M-type (metallic), or S-type (silicaceous).
Accretion (astrophysics)In astrophysics, accretion is the accumulation of matter into a massive object by gravitationally attracting more matter. If the matter is gaseous the result is an accretion disc. Accretion of solid matter such as dust will form larger solid objects. Most astronomical objects, such as galaxies, stars, and planets, are formed by accretion processes.
Planetary-mass objectA planetary-mass object (PMO), planemo, or planetary body (sometimes referred to as a world) is, by geophysical definition of celestial objects, any celestial objectmassive enough to achieve hydrostatic equilibrium and assume an ellipsoid shape, but not enough to sustain corefusion like a star.
Primary bodyPrime astronomical designated entity within a gravitational system Motion of the Solar System's barycenter relative to the Sun A primary body – also called a central body, host body, gravitational primary, or simply primary – is the main physical body of a gravitationally bound, multi-object system. This object constitutes most of that system's mass and will generally be located near the system's barycenter.
Circumplanetary diskA circumplanetary disk (or circumplanetary disc, short CPD) is a torus, pancake or ring-shaped accumulation of matter composed of gas, dust, planetesimals, asteroids or collision fragments in orbit around a planet. They are reservoirs of material out of which moons (or exomoons or subsatellites) may form. Such a disk can manifest itself in various ways.*As an Amazon Associate I earn from qualifying purchases.