Cosmic Know-It-All or Space Cadet?

[A] Mercury | Mercury hugs the Sun in the tightest orbit. It’s the smallest planet and nearest to our star, racing around it every 88 days while enduring intense sunlight and wild temperature swings.

[D] Venus | Thick carbon‑dioxide air and clouds trap heat on Venus in a runaway greenhouse effect. Surface temperatures are hot enough to melt lead, easily topping scorched Mercury despite its greater distance.

[B] Jupiter | Jupiter spins once in roughly 10 hours. That turbo rotation flattens the planet at the poles and helps drive its banded winds and monster storms across the cloud tops.

[A] Venus | Venus rotates so slowly that a single spin takes about 243 Earth days, longer than a Venusian year. If you lived there, sunrise would be a rare and confusing event.

[B] Neptune | Uranus and Neptune are the ice giants. They’re dominated by heavier volatiles like water, ammonia, and methane, distinct from the hydrogen‑helium mix of the gas giants Jupiter and Saturn.

[A] Saturn | Saturn’s average density is less than water. It’s mostly hydrogen and helium, so in the bathtub thought experiment, Saturn would float while the rocky worlds would sink fast.

[C] Earth | Earth leads in average density among planets, about 5.51 g/cm³. A metal‑rich core and compressed interior make our world denser than Mercury, Venus, and the gas and ice giants.

[A] Jupiter | Jupiter’s Great Red Spot is a gigantic high‑pressure storm, larger than Earth and centuries old. Juno measurements show the vortex extends hundreds of kilometers below the visible clouds.

[C] Saturn | Saturn’s north pole sports a six‑sided jet stream. Cassini watched the hexagon circulate for years, a stable, speedy feature that still puzzles atmospheric scientists.

[B] Mars | Iron minerals in Martian dust oxidize, tinting the landscape rust‑red to human eyes. The nickname predates spacecraft and appears in many ancient cultures’ names for Mars.

[B] Mars | Olympus Mons is a massive shield volcano on Mars, towering over 20 kilometers. Low gravity and lack of plate tectonics let it grow broader and taller than Earth’s volcanoes.

[C] Saturn | All four giant planets have rings, but Saturn’s are wide, bright, and easily seen in small telescopes. They’re mostly water‑ice chunks tracing the planet’s gravity and resonances.

[B] Axial tilt | Earth’s axis is tilted about 23.5 degrees. As the planet orbits the Sun, that tilt changes the angle of sunlight and daylight length by hemisphere, creating spring, summer, fall, and winter.

[D] Tidal locking | The Moon rotates once for each orbit, a synchronized state called tidal locking. Gravity and friction slowed its spin long ago, leaving the same hemisphere facing Earth.

[A] 29.5 days | From new moon to new moon is the synodic month, about 29.5 days. That’s longer than the Moon’s orbital period because Earth moves around the Sun during that cycle.

[D] Proxima Centauri | Proxima Centauri, a faint red dwarf just over four light‑years away, is the closest known star to the solar system. It’s part of the Alpha Centauri stellar neighborhood.

[C] Jupiter | Jupiter dominates the solar system’s planet lineup by size and mass. Its gravity shapes asteroid families, shepherds trojans, and wrangles dozens of moons into complex resonant dances.

[B] Mercury | Mercury is the smallest planet and nearest to the Sun. Despite intense sunlight, it’s not the hottest world — that title belongs to greenhouse‑dominated Venus.

[D] Ganymede | Ganymede, a Jovian moon, is larger than Mercury and likely hides a deep subsurface ocean. Its magnetic field and layered interior make it a standout in the outer solar system.

[A] Titan | Titan’s nitrogen‑rich air is denser than Earth’s. Cassini‑Huygens mapped rivers, lakes, and seas of liquid methane and ethane, revealing a hydrocarbon weather cycle in deep‑freeze conditions.

[C] Io | Jupiter’s moon Io erupts constantly. Tidal flexing from Jupiter and neighboring moons pumps heat into its interior, powering lava fountains and endlessly resurfacing its face.

[B] Enceladus | Cassini flew through geyser‑like plumes from Enceladus’s south‑polar fractures, tasting water ice, salts, and organics. The spray feeds Saturn’s E ring and hints at a salty global ocean below.

[C] 8 minutes 20 seconds | At one astronomical unit, light needs about 8 minutes 20 seconds to cross the Sun–Earth distance. You always see the Sun as it was several minutes in the past.

[D] Uranus | Uranus is so tipped it effectively rolls around the Sun. The extreme tilt delivers decades‑long seasons and unusual lighting at the poles.

[D] Jupiter | Gas giants are dominated by hydrogen and helium. Jupiter and Saturn fit this class, while Uranus and Neptune are classified as ice giants due to heavier volatile ingredients.

[A] Earth | Terrestrial planets — Mercury, Venus, Earth, and Mars — are rocky with solid surfaces. They differ sharply from the giant planets, which lack solid ground under their clouds.

[B] Red dwarfs | Small, cool red dwarfs dominate our galaxy’s population. They burn fuel slowly and can live for trillions of years, far longer than stars like the Sun.

[C] 88 | Modern astronomy divides the entire sky into 88 official constellations. The International Astronomical Union adopted these boundaries so every point on the sky belongs to exactly one constellation.

[A] Around the Sun beyond Neptune | The Kuiper Belt is a ring of icy bodies beyond Neptune, home to dwarf planets like Pluto and many comets. It extends outward into the scattered disk and deep space.

[D] Mars | A Martian day, called a sol, lasts about 24.6 hours. That near‑match makes daily operations and sleep schedules on Mars missions far simpler than on the outer planets.