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Loading contentSpace is not empty — it is filled with radiation, plasma, and debris that threaten spacecraft and astronauts. This encyclopedia maps the hazards of space, from the Sun's storms to the cosmic rays of the galaxy, and the missions that watch for them.
The Sun-driven phenomena — solar wind, flares, coronal mass ejections, geomagnetic storms, and auroras — that shape near-Earth space.
8 entriesThe particle-radiation hazards of space — the Van Allen belts, galactic cosmic rays, and solar energetic particles.
4 entriesThe physical hazards that threaten spacecraft — orbital debris, micrometeoroids, charging, and atomic oxygen.
5 entriesThe indices and scales that quantify space weather — Kp, Dst, and the NOAA G/S/R scales.
5 entriesThe Sun-driven phenomena that shape near-Earth space.
The continuous stream of charged particles — mostly protons and electrons — that flows outward from the Sun's corona at hundreds of kilometres per second, filling the Solar System and shaping planetary magnetospheres.
A sudden, intense burst of radiation from the Sun's surface, released when magnetic energy in the corona is explosively reconfigured. The X-rays arrive in minutes and can ionise Earth's upper atmosphere, causing radio blackouts.
An enormous eruption of magnetised plasma from the Sun's corona, launching billions of tonnes of material into space. When aimed at Earth, a CME can drive the largest geomagnetic storms one to three days later.
A temporary disturbance of Earth's magnetosphere, driven by the arrival of a fast solar wind or a coronal mass ejection. Strong storms can disrupt satellites, power grids, and navigation, and drive bright auroras.
The glow produced when energetic particles from the magnetosphere spiral down Earth's magnetic-field lines and excite gases in the upper atmosphere — the visible signature of space weather over the polar regions.
The region around a planet dominated by its magnetic field, which deflects the solar wind and traps charged particles. Earth's magnetosphere shields the surface from most space radiation.
The vast bubble of solar wind and magnetic field that surrounds the entire Solar System, carving out a cavity in the surrounding interstellar medium and shielding the planets from a fraction of the galactic cosmic rays.
The outer boundary of the heliosphere, where the outward pressure of the solar wind balances the pressure of the interstellar medium — the edge of the Sun's domain, crossed by the two Voyager spacecraft.
High-energy charged particles that stream through space near the speed of light. They come from the Sun (solar energetic particles) and from beyond the Solar System (galactic cosmic rays), and are a primary radiation hazard for astronauts.
Extremely energetic charged particles from outside the Solar System — the remnants of supernovae and other violent events. They pervade deep space, are hard to shield against, and pose the dominant long-term radiation risk on missions to Mars.
Bursts of high-energy particles accelerated by solar flares and coronal mass ejections. Unlike the steady galactic cosmic rays, SEP events are sudden and can deliver a dangerous radiation dose to astronauts within hours.
Two (sometimes more) doughnut-shaped zones of energetic charged particles trapped by Earth's magnetic field. Spacecraft crossing the belts — and those in orbits within them — must be hardened against the intense radiation.
Defunct satellites, spent rocket stages, and fragments left in Earth orbit. Travelling at kilometres per second, even a small piece can destroy a working spacecraft, and collisions create more debris — a growing hazard in low Earth orbit.
Tiny natural particles — grains of comet and asteroid dust — moving at tens of kilometres per second. They erode surfaces and can puncture spacecraft; together with orbital debris they define the impact hazard for spacecraft.
The build-up of electric charge on a spacecraft as it moves through the space plasma, especially during geomagnetic storms. A sudden discharge can damage electronics — a leading cause of space-weather-related spacecraft anomalies.
Single oxygen atoms that dominate the thin atmosphere of low Earth orbit. Highly reactive, atomic oxygen slowly erodes exposed spacecraft materials, a design concern for anything operating for long periods in LEO.
The ionised gas that pervades near-Earth space, from the ionosphere out through the magnetosphere. Its density and energy govern spacecraft charging, radio propagation, and the behaviour of the radiation belts.
The spacecraft and centres that watch the Sun and the space environment.
Each phenomenon, radiation environment, hazard, and index is a first-class knowledge-graph entity resolved through the Scientific Data Engine, reusing the Sun, the planets, and the solar missions. This encyclopedia states no live conditions — for current space weather, see NOAA's Space Weather Prediction Center. Unknown values are left blank. See source quality.