Meteor showers feel magical, but they are wonderfully predictable once you know what is happening. Every "shooting star" in a shower is a grain of ancient comet dust meeting the Earth at enormous speed. Here is the science, and what the jargon on our shower pages actually means.

Where the dust comes from

As a comet loops around the Sun, the Sun's heat boils off gas and dust, leaving a trail of tiny particles strewn along the comet's orbit. When the Earth's orbit crosses that trail — which happens on the same dates each year, because both orbits are fixed — we sweep through the debris and see a meteor shower. Most particles are no bigger than a grain of sand.

The material hits the atmosphere at tens of kilometres per second. It is not the rock "burning up" from friction so much as the air in front of it being violently compressed and heated, which vaporises the particle and makes the surrounding air glow. That glowing streak, 80–120 km up, is the meteor. The particle itself is almost always destroyed long before it could reach the ground.

Each major shower has a parent body: the Perseids come from Comet 109P/Swift–Tuttle, the Leonids from Tempel–Tuttle, and so on. The Geminids are a famous exception — their parent is a rocky asteroid, 3200 Phaethon, which behaves oddly like a comet. That is a big part of why the Geminids are so dense and reliable.

Radiants and why showers are named after constellations

Because all the particles in a stream travel in parallel, perspective makes the meteors appear to diverge from a single point in the sky — the radiant — just as parallel railway tracks seem to spring from a point on the horizon. A shower is named after the constellation its radiant sits in: the Perseids radiate from Perseus, the Geminids from Gemini, the Orionids from Orion.

This is also why you should not stare straight at the radiant. Meteors there are heading almost directly towards you and leave short trails; the long, memorable streaks appear well away from it.

Reading the ZHR

Shower strength is quoted as a ZHR — the zenithal hourly rate. It is a standardised, idealised number: how many meteors one observer would see per hour if the sky were perfectly dark and the radiant were straight overhead (at the zenith). It exists so different showers and years can be compared fairly.

In practice you will almost always see fewer, because:

  • Light pollution erases the fainter meteors (often most of them).
  • A low radiant means many meteors happen below your horizon.
  • Moonlight, haze and tiredness all take their toll.

So treat a ZHR of 100 as "excellent shower, get somewhere dark", not "I will count 100". Our how to watch a meteor shower guide covers how to get as close to the ideal as you can.

Sporadics, fireballs and the vocabulary

  • Sporadic meteors are the background of random meteors — not part of any shower — that you see on any dark night, a few per hour.
  • Fireballs and bolides are exceptionally bright meteors, brighter than the planet Venus, sometimes casting shadows or ending in a visible flash. They come from larger particles and are the ones people remember for years.
  • The words trip people up: a meteoroid is the particle in space, a meteor is the streak of light it makes in the atmosphere, and a meteorite is the rare survivor that actually reaches the ground. Shower meteors essentially never produce meteorites — they are far too small.

Ready to put it into practice? Check the 2026 meteor shower calendar for peak dates and moon conditions.