Planets

Cards · 53

Planet

A celestial body orbiting a star that is massive enough to be rounded by its own gravity and has cleared its orbital path.

Terrestrial planet

A rocky planet composed mostly of silicate rocks or metals with a solid surface, such as Mercury, Venus, Earth, and Mars.

Gas giant

A large planet composed mostly of hydrogen and helium gases, specifically Jupiter and Saturn in our solar system.

Ice giant

A giant planet composed mainly of elements heavier than hydrogen and helium, such as water, ammonia, and methane, like Uranus and Neptune.

Dwarf planet

A celestial body orbiting the Sun that is spherical due to its gravity but has not cleared the neighborhood around its orbit.

Astronomical Unit (AU)

The average distance between Earth and the Sun, approximately 149.6 million kilometers (93 million miles).

Mercury

Closest planet to the Sun (0.39 AU), smallest major planet, rocky composition with no atmosphere and extreme temperature swings.

Mercury's core

Contains an unusually large metallic iron core comprising about 85% of the planet's total radius.

Caloris Basin

One of the largest impact basins in the Solar System, located on Mercury, measuring about 1,550 km in diameter.

Venus

Second planet from the Sun (0.72 AU), rocky composition, Earth-sized, with a runaway greenhouse effect and surface temperatures of 465°C.

Venus's atmosphere

Extremely dense atmosphere composed of 96.5% carbon dioxide, with clouds of sulfuric acid and 92 times Earth's surface pressure.

Retrograde rotation of Venus

Rotates from east to west, opposite to most planets, taking 243 Earth days to complete a single rotation.

Earth

Third planet from the Sun (1.0 AU), largest terrestrial planet, uniquely possessing liquid surface water, plate tectonics, and life.

Earth's atmosphere

Composed of 78% nitrogen, 21% oxygen, and 1% argon and trace gases, shielded by a strong global magnetic field.

The Moon

Earth's only natural satellite, roughly one-quarter Earth's diameter, orbiting at an average distance of 384,400 km.

Mars

Fourth planet from the Sun (1.52 AU), second-smallest planet, rocky and dusty with an iron-rich surface giving it a reddish hue.

Mars's atmosphere

Thin atmosphere composed primarily of carbon dioxide (95%), with less than 1% of Earth's atmospheric pressure.

Olympus Mons

A massive shield volcano on Mars, the tallest planetary mountain in the Solar System at approximately 21.9 km high.

Valles Marineris

A vast canyon system along the Martian equator spanning over 4,000 km in length and up to 7 km deep.

Phobos and Deimos

The two small, irregularly shaped moons of Mars, widely believed to be captured carbonaceous asteroids.

Asteroid Belt

Toroidal region between Mars and Jupiter containing millions of rocky and metallic bodies, including the dwarf planet Ceres.

Ceres

The largest object in the asteroid belt and the only dwarf planet located within the inner Solar System.

Jupiter

Fifth planet from the Sun (5.2 AU), largest planet in the solar system, composed mainly of hydrogen and helium gas.

Great Red Spot

A persistent high-pressure anticyclonic storm on Jupiter, larger than Earth, that has raged for at least 300 years.

Jupiter's magnetic field

The strongest planetary magnetic field in the Solar System, roughly 14 times stronger than Earth's.

Io

Innermost Galilean moon of Jupiter, the most geologically active and volcanically eruptive body in the Solar System.

Europa

Galilean moon of Jupiter possessing a smooth ice crust overlying a subsurface liquid water ocean that may harbor life.

Ganymede

Largest moon in the Solar System, larger than Mercury, and the only known moon with its own magnetic field.

Callisto

Outermost Galilean moon of Jupiter, heavily cratered and geologically dead, composed of equal parts rock and ice.

Saturn

Sixth planet from the Sun (9.58 AU), second-largest planet, famous for its extensive and prominent planetary ring system.

Saturn's rings

Composed of billions of small chunks of ice and rock dust extending up to 282,000 km from the planet but only tens of meters thick.

Saturn's density

The least dense planet in the Solar System (0.687 g/cm³), low enough that it would float in water.

Titan

Saturn's largest moon, the only moon with a dense nitrogen-rich atmosphere, featuring lakes and rivers of liquid methane and ethane.

Enceladus

Icy moon of Saturn known for cryovolcanic geysers erupting water vapor and organic molecules from a global subsurface ocean.

Uranus

Seventh planet from the Sun (19.2 AU), an ice giant with a blue-green color caused by atmospheric methane.

Uranus's axial tilt

Rotates nearly on its side with an axial tilt of 97.8 degrees, resulting in extreme seasonal variations.

Uranus's ring system

A faint, narrow system of 13 known rings composed of extremely dark, boulder-sized particles.

Titania and Oberon

The two largest of Uranus's 28 known moons, both composed of roughly equal parts water ice and silicate rock.

Miranda

Smallest of Uranus's major moons, exhibiting extreme, chaotic surface geology with massive fault canyons up to 20 km deep.

Neptune

Eighth planet from the Sun (30.1 AU), the densest ice giant, featuring vibrant blue coloration and the fastest recorded winds.

Neptune's winds

Reaches supersonic speeds exceeding 2,100 km/h (1,300 mph), the fastest atmospheric winds in the Solar System.

Great Dark Spot

A series of large, Earth-sized cyclonic storms in Neptune's southern hemisphere, first observed by Voyager 2 in 1989.

Triton

Neptune's largest moon, uniquely featuring a retrograde orbit, active nitrogen geysers, and a composition similar to Pluto.

Kuiper Belt

Circumstellar disc extending beyond Neptune (30 to 55 AU) populated by tens of thousands of icy bodies and dwarf planets.

Pluto

Dwarf planet in the Kuiper Belt (39.5 AU average), composed of rock and ice, reclassified from major planet status in 2006.

Charon

Largest of Pluto's five moons, so massive compared to Pluto that they form a mutually tidally locked binary system.

Eris

Massive dwarf planet in the scattered disc (68 AU average), whose 2005 discovery led to the formal IAU definition of a planet.

Haumea

Elongated, egg-shaped dwarf planet in the Kuiper Belt with a fast 4-hour rotation and two small moons.

Makemake

Bright dwarf planet in the Kuiper Belt with an extremely cold surface covered in methane, ethane, and nitrogen ices.

Exoplanet

Any planet located outside our Solar System orbiting another star, stellar remnant, or drifting freely in interstellar space.

Hot Jupiter

A class of gas giant exoplanets with orbital periods of less than 10 days, located extremely close to their parent stars.

Super-Earth

An extrasolar planet with a mass larger than Earth's but substantially lower than that of ice giants like Uranus and Neptune.

Habitable zone

The orbital region around a star where liquid water can stably exist on the surface of a planet under sufficient atmospheric pressure.