Space Encyclopedia
Space Encyclopedia
14 plain-English guides to space and space weather. Each one explains the science, lists the key facts, answers common questions, and links to the live trackers that show the same thing happening right now.
Earth
Earth explained — our planet's structure, atmosphere, magnetic field, and how space weather from the Sun affects life here.
The Solar System
The Solar System — the Sun, eight planets, dwarf planets, moons, asteroids and comets, and how they interact through gravity and solar wind.
Comets
Comets — icy bodies from the outer Solar System whose glowing tails appear when solar wind and radiation vaporize their surface.
Asteroids
Asteroids — rocky remnants of the early Solar System, their orbits, sizes, and how planetary defense tracks Near-Earth Objects.
Meteor Showers
Meteor showers — when Earth crosses a comet's dust trail. Peak dates, radiants, and how to watch the Perseids, Geminids and more.
Stars
Stars — how they form, live, and die. Spectral classes, main sequence, red giants, supernovae, and how to find bright stars tonight.
Satellites & Spacecraft
Satellites and spacecraft — what they do, how orbits work, and why solar storms can drag them lower or knock them out entirely.
Aurora
Aurora borealis and aurora australis — how solar wind and Earth's magnetic field create the northern and southern lights, and how to see them.
Stargazing
Stargazing — how to find dark skies, read a star chart, and identify planets, constellations, and deep-sky objects tonight.
Galaxies & Nebulas
Galaxies and nebulas — the Milky Way, Andromeda, spiral and elliptical galaxies, star-forming nebulas, and where to find them in the sky.
Exoplanets
Exoplanets — planets orbiting other stars. Discovery methods, habitable zones, and the search for Earth-like worlds.
Space Missions
Space missions — from Apollo to Voyager, JWST, Artemis, and Mars rovers. Landmark human and robotic exploration of the Solar System.
IMF Bz Orientation
The interplanetary magnetic field's Bz component — why a southward orientation opens Earth's magnetosphere to solar wind and drives auroral storms.
Coronal Mass Ejections (CMEs)
Coronal mass ejections — massive eruptions of solar plasma and magnetic field, their travel time to Earth, and their role in the strongest geomagnetic storms.
Looking for definitions? See the glossary, or the longer Space Academy guides.