40 Fun Facts About Solar System & Space

Which planet is known as the Red Planet?

Mars is the Red Planet: its colour comes from dust and sand rich in reddish iron oxides, essentially rust, spread across its plains.

How many planets are in our solar system?

The count fell from nine to eight when Pluto was reclassified as a dwarf planet in 2006.

Which planet is closest to the Sun?

Mercury is the closest planet to the Sun, orbiting at an average distance of about 57.9 million kilometers.

Who was the first human to travel to space?

Yuri Gagarin ejected from Vostok 1 about 7 km above the ground and parachuted down separately from his capsule.

Which Apollo mission first landed astronauts on the Moon?

Neil Armstrong partly piloted Apollo 11's lunar module by hand to find a safe place to set it down.

What is the hottest planet in our solar system?

Venus is only the second planet from the Sun, yet its thick carbon dioxide atmosphere traps so much heat that its surface tops 460°C.

What is the asteroid belt located between?

The gravity of newly formed Jupiter stirred up the rocks between Mars and Jupiter, so they smashed together instead of building a planet.

Which NASA rover landed on Mars in February 2021 to search for signs of ancient life?

Perseverance landed in Jezero Crater, once a lake with a river delta, and has been sealing rock cores in tubes that a future mission could bring to Earth.

What is the primary composition of the Sun?

The Sun is mostly hydrogen and helium, and its core fuses hydrogen into helium, releasing the energy that makes it shine.

Who was the first American woman in space?

Sally Ride kept her 27-year relationship with Tam O'Shaughnessy private, and it became public only in her obituary in 2012.

Which space telescope, launched in 2021, primarily observes in infrared wavelengths?

The James Webb Space Telescope must stay extremely cold so its own heat doesn't drown out faint infrared light, so a five-layer sunshield keeps it in shade.

Which craft made the first powered, controlled flight on another planet?

Ingenuity was built to make just five test flights, but it flew 72 times over nearly three years.

What is the Great Red Spot?

The Great Red Spot is a giant storm wider than Earth, and NASA's Juno spacecraft flew over it in July 2017, photographing its tangled clouds.

Who is credited with discovering the four largest moons of the biggest planet in 1610?

Galileo Galilei gets the credit, though Simon Marius spotted the same four moons at about the same time, and his names for them stuck.

What is the tallest volcano in the solar system?

Olympus Mons likely grew so tall because the crust beneath it stayed over one hot spot, so lava kept piling up in the same place.

What are the rings of the second-largest planet made almost entirely of?

The rings are almost pure water ice, and that bright, clean ice is one clue that they may be much younger than the planet itself.

What region of the solar system lies beyond Neptune's orbit and contains Pluto?

Pluto, found in 1930, was the first Kuiper Belt object ever discovered, spotted before astronomers had any reason to expect such a belt.

What does one astronomical unit (AU) represent?

The AU began as the distance from the Sun to Earth, but relativity made its old definition too complicated, so in 2012 the IAU fixed it at an exact number of metres.

Which NASA mission flew past Pluto in 2015, providing the first close-up images?

New Horizons carried some of Clyde Tombaugh's ashes, so the astronomer who discovered Pluto made the journey there too.

What is the largest moon in our solar system?

Ganymede makes its own magnetic field, which lights up auroras around its poles, and it likely hides an underground saltwater ocean.

Approximately how far is one light-year?

One light-year is about 9.46 trillion kilometers, so light from Proxima Centauri, the nearest star after the Sun, takes over four years to reach us.

Which spacecraft became the first to enter interstellar space?

Voyager 1 launched in 1977 to fly past Jupiter and Saturn, and as of 2026 it was still sending data home from interstellar space.

Which planet could theoretically float in water due to its low density?

Saturn's rapid spin makes it bulge, so its equatorial radius is more than 10% longer than its polar radius.

What did Neil Armstrong and Buzz Aldrin name their landing site on the Moon?

After touching down, Neil Armstrong radioed, 'Houston, Tranquility Base here. The Eagle has landed.'

Which planet is tilted almost on its side, with an axial tilt of about 98 degrees?

Uranus rolls around the Sun almost on its side, so each pole spends decades in continuous sunlight and then decades in darkness.

Which moon of Saturn has liquid methane lakes on its surface?

Titan's methane falls as rain, carving rivers and filling lakes in a cycle much like the water cycle on our own planet.

Which dwarf planet is the only confirmed one inside the main asteroid belt?

Ceres's mysterious bright spots, seen up close by NASA's Dawn, turned out to be salt deposits left by briny water seeping up from below.

Which moon in our solar system is the most volcanically active body?

Io has hundreds of active volcanoes, heated by a tug-of-war between Jupiter's gravity and the pulls of its neighbouring moons.

What message for aliens does each Voyager probe carry?

Each Voyager carries a golden record whose contents a committee chaired by Carl Sagan chose, while the earlier Pioneer probes carried plaques.

Which planet has the fastest winds in the solar system?

Neptune's winds reach about 2,000 km/h despite the planet's great distance and the weak sunlight it receives.

What is the largest moon of Pluto?

Charon and Pluto are tidally locked to each other, so each always keeps the same face turned toward the other.

What is the approximate temperature at the Sun's core?

The Sun's core reaches approximately 15 million degrees Celsius (27 million °F), hot enough to sustain nuclear fusion reactions that power the star.

Where are most long-period comets thought to come from?

Now and then something disturbs the orbit of an icy body in the Oort Cloud, and it begins a long fall toward the Sun.

Which planet is the densest in our solar system?

Earth is the densest planet, just ahead of Mercury, even though Mercury's metal core fills about 85% of that planet's radius.

Which planet has the largest known magnetic field in the solar system?

Jupiter's magnetic field traps such intense radiation that NASA's Juno probe keeps its electronics inside a titanium vault.

Which Saturn moon sprays geysers into space from an ocean hidden beneath its crust?

Enceladus's geysers let NASA's Cassini probe sample that hidden ocean by flying straight through the plumes.

What flaw blurred the Hubble Space Telescope's first images?

Hubble's misshapen main mirror had been ground incorrectly, and astronauts fitted corrective optics during a 1993 shuttle repair mission.

Which comet returns about every 76 years and last swung through the inner solar system in 1986?

Mark Twain was born just after Halley's Comet appeared in 1835, predicted he would go out with it, and died the day after its 1910 return.

What was the first spacecraft to orbit another planet?

Mariner 9 entered orbit around Mars in November 1971, narrowly beating the Soviet Mars 2 probe, and had to wait out a global dust storm before mapping the surface.

What is the name of the boundary where the Sun's solar wind gives way to interstellar space?

NASA's IBEX spacecraft maps the region around the heliopause from orbit, and its first maps showed a bright, winding ribbon nobody had predicted.