10 missions and 150 questions on space weather, aurora, the Moon and eclipses, planets, stars, black holes, telescopes, rockets, meteors and comets, and the Earth-Sun connection. Each answer is explained and reviewed against NOAA and NASA sources (last reviewed 10 October 2026).
☀️ Space Weather mission
Kp, flares, CMEs and NOAA's G, S and R scales. Live solar flares →
What does the S in NOAA's S scale stand for?
Solar radiation storms. NOAA SWPC's S scale rates solar radiation storms by the flux of energetic protons (10 MeV or more) near Earth. S1 starts at 10 particle flux units and each level is ten times the one before. Flares are rated on the R scale and geomagnetic storms on the G scale.
Which flare peak matches an R5 (extreme) radio blackout on NOAA's scale?
X20 or greater. NOAA's R scale maps flare peak X-ray flux to radio blackouts: X1 is R3, X10 is R4 and X20 is R5. An R5 means a complete HF radio blackout on the sunlit side of Earth for hours. NOAA SWPC lists these thresholds on its scales page.
Which letter is NOAA's scale for geomagnetic storms?
G. NOAA uses three scales: G for geomagnetic storms, S for solar radiation storms and R for radio blackouts, each running from 1 (minor) to 5 (extreme). K is part of the Kp index that feeds the G scale.
🌌 Aurora & Geomagnetic Storms mission
The oval, Kp visibility and why aurora has color. Live aurora forecast →
The aurora australis occurs mainly near which pole?
South Pole. Aurora australis, the southern lights, ring the south magnetic pole and are best seen from Antarctica, southern Australia, New Zealand and southern South America. The northern counterpart is aurora borealis.
At roughly what heights does most visible aurora occur?
100 to 300 km. Most visible aurora glows in the thermosphere, roughly 100 to 300 km above Earth. Lower, green emission is typically near 100 to 150 km, and rarer red glow reaches 200 km and up. NASA's aurora imagery from the ISS orbit looks down on these layers.
What lights up the aurora?
Charged particles colliding with atmospheric gases. Electrons and protons guided by Earth's magnetic field hit oxygen and nitrogen high in the atmosphere. The excited atoms release the extra energy as light. NASA describes it as similar to a neon sign.
🌙 Moon & Eclipses mission
Phases, lunar eclipses and solar eclipses. Eclipse guides →
How wide can the path of totality of a total solar eclipse be, at most?
About 270 km. The Moon's umbral shadow is small: the path of totality is never wider than about 270 km (167 miles), per NASA eclipse calculations. Outside it, observers see only a partial eclipse.
An annular eclipse happens when the Moon is...
Near apogee and looks too small to cover the Sun. When the Moon is near its farthest point (apogee) it appears slightly smaller than the Sun and leaves a bright ring called the ring of fire. It is never fully dark, so NASA says eye protection is needed throughout.
When is it safe to look at the Sun without eye protection?
Only during the brief total phase of a total eclipse. Only during the few minutes of total eclipse, when the Moon completely covers the Sun, is it safe to look without a filter. NASA says to use certified solar eclipse glasses at all other times, including partial phases.
🪐 Planets & Solar System mission
Orbits, moons and the worlds around the Sun. Planets tonight →
Which is the smallest planet in the Solar System?
Mercury. Mercury is the smallest planet, only slightly larger than Earth's Moon, at about 4,880 km across. Pluto is a dwarf planet, not a planet. NASA's MESSENGER mission mapped it fully.
About how many Earth years does Neptune take to orbit the Sun?
165. Neptune takes about 165 Earth years for one trip around the Sun, and in 2011 it completed its first orbit since its discovery in 1846. Uranus takes 84 years and Saturn about 29. NASA's Neptune fact sheet lists it.
Mercury's year, one orbit of the Sun, lasts about how many Earth days?
88. Mercury is closest to the Sun and moves fastest, completing an orbit in about 88 Earth days. Venus takes 225 days and Mars 687. NASA's planetary fact sheets list these periods.
⭐ Stars & Stellar Life mission
The H-R diagram, supernovae and nebulae. Space Academy →
What type of star is the Sun?
A G-type main-sequence star. The Sun is a G2 main-sequence star, sometimes called a yellow dwarf, fusing hydrogen into helium in its core. NASA says it is about halfway through its roughly 10-billion-year main-sequence life.
About how old is the Sun?
4.6 billion years. The Sun and Solar System formed about 4.6 billion years ago, as dated from meteorites. The universe is older, about 13.8 billion years.
What powers a star like the Sun?
Nuclear fusion of hydrogen into helium. In the Sun's core at about 15 million degrees, hydrogen nuclei fuse into helium and release energy, according to NASA. About 600 million tons of hydrogen are converted every second.
🕳️ Black Holes & Deep Space mission
Event horizons, JWST and light-years. Space Academy →
What is a black hole's event horizon?
The boundary beyond which nothing can escape. The event horizon is the point of no return around a black hole where the escape speed exceeds the speed of light. It is not a solid surface. NASA describes it as the boundary of the black hole itself.
The first image of a black hole, released in 2019, showed the black hole in which galaxy?
M87. The Event Horizon Telescope collaboration imaged the shadow of the supermassive black hole at the center of galaxy M87, about 55 million light-years away, with a mass of roughly 6.5 billion Suns. It was the first direct image of a black hole's shadow.
The 2022 image of Sagittarius A* showed a black hole with a mass of about...
4 million Suns. Sagittarius A*, the Milky Way's central black hole, has about 4 million solar masses and lies roughly 26,000 light-years away. The Event Horizon Telescope released its first image in May 2022.
🔭 Telescopes & Observation mission
Optics, magnitude, seeing and observing skills. Stargazing tonight →
What does a reflecting telescope use to collect light?
A curved mirror. Reflectors use a large curved primary mirror to gather light, while refractors use lenses. Mirrors can be made much larger, so almost every big research telescope, including JWST, is a reflector.
Which telescope specification matters most for seeing faint objects?
Aperture. Aperture, the diameter of the main lens or mirror, sets how much light is gathered and the finest detail you can resolve. Magnification matters less because it only enlarges what the aperture collects.
How is a telescope's magnification calculated?
Telescope focal length divided by eyepiece focal length. Magnification equals the telescope's focal length divided by the eyepiece's focal length, so a 1000 mm scope with a 10 mm eyepiece gives 100x. Useful power is limited by aperture and atmosphere.
🚀 Rockets & Exploration mission
Delta-v, orbits, the ISS and Artemis. Space Academy →
Which of Newton's laws explains how a rocket moves?
The third: every action has an equal and opposite reaction. A rocket throws exhaust backward and the equal and opposite reaction pushes it forward. NASA teaches this with Newton's third law. It works in a vacuum because it needs no air to push against.
What does delta-v measure for a spacecraft?
The total change in velocity its propellant can provide. Delta-v is the change in velocity a spacecraft can achieve with its propellant. Mission designers add up the delta-v needed for each maneuver, such as launch, orbit changes and landings.
About how fast must something travel to stay in low Earth orbit?
About 7.8 km/s (28,000 km/h). An object orbits at low Earth altitude by moving sideways at roughly 7.8 km/s (about 28,000 km/h), so it keeps falling around Earth. NASA says the ISS travels at this speed.
🌠 Meteors & Comets mission
Showers, radiants and comet tails. Sky tonight →
A meteor that survives to hit the ground is called a...
Meteorite. A meteoroid is the particle in space, the meteor is the streak of light as it burns up, and a meteorite is any piece that lands. NASA uses these three terms.
Most meteors seen in a shower are caused by particles about the size of what?
A grain of sand or small pebble. Most shower meteors come from dust and grains the size of sand to a pea, burning up around 80 to 100 km above Earth. NASA's Meteoroid Environment Office tracks bigger ones.
What is a meteor shower's radiant?
The point in the sky from which meteors seem to originate. Meteors in a shower travel on parallel paths, but perspective makes them appear to radiate from one point, which names the shower, such as Perseus for the Perseids. The IAU names showers after the constellation holding the radiant.
🌍 Earth-Sun Connection mission
Solar wind, the magnetosphere and the Sun itself. Live solar wind →
What is the typical solar wind speed at Earth?
300 to 800 km/s. Near Earth the solar wind usually blows between about 300 and 800 km/s, with slow wind near 400 and fast streams from coronal holes near 700 or more. NOAA's DSCOVR measures it live.
What is the solar wind mostly made of?
Charged particles: protons and electrons. The solar wind is a stream of plasma, mostly protons and electrons with some helium nuclei, carrying the Sun's magnetic field into space. NASA's Parker and SOHO missions study it.
What is Earth's magnetosphere?
The region around Earth controlled by its magnetic field. The magnetosphere is the bubble carved out of the solar wind by Earth's magnetic field. It deflects most charged particles and protects the atmosphere, NASA explains.
Space Trivia by Category FAQ
What is Space Trivia by Category?
A free trivia game with 10 missions, one per topic, from space weather and aurora to black holes and rockets. Each mission has 15 questions in the bank and you play 10 per attempt.
How do I pass a mission?
Answer at least 60% correctly, which is 6 of 10. Your best score for each mission is saved on your device only.
Are the answers accurate?
Each question was reviewed on 10 October 2026 against NOAA Space Weather Prediction Center, NASA and other primary sources, and every explanation links to the matching Academy page.
