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Meteor Showers
The one thing in the sky that needs no equipment at all, and the easiest night out here.
Seeing it from the UK
This is the easiest thing on this whole site to see, and the only one where equipment makes it worse: binoculars and telescopes narrow your view, and you want as much sky as possible. Lie back somewhere dark, give your eyes twenty minutes to adjust, and do not stare straight at the radiant, because meteors near it are shortened by perspective and the long dramatic ones appear well away from it. After midnight beats before it, since by then your side of the Earth is facing into the stream. The Moon matters more than anything else: a bright one will wipe out all but the best. The Perseids in August and the Geminids in December are the two reliable ones from here.
A meteor shower is the Earth driving through a trail of dust. Comets shed grit every time they pass the Sun, and that grit stays spread along the comet’s orbit for centuries. Where our orbit crosses one of those trails we run into it, and we do so on the same dates every year, which is why showers are diary events rather than surprises.
The grains are tiny. Most of what you see is the size of a grain of sand, hitting the top of the atmosphere at tens of kilometres a second and burning up around eighty to a hundred kilometres above your head. The streak is not the grain glowing, it is the air along its path, which is why a meteor can look far bigger than the thing causing it.
They all seem to come from one point in the sky, and that is pure perspective, the same reason railway lines appear to meet in the distance. The point is called the radiant, and the shower takes its name from whichever constellation it sits in. The Perseids radiate from Perseus, the Geminids from Gemini.
Not all of them come from comets. The Geminids in December, which are the best of the year, come from an object called Phaethon that behaves more like an asteroid, and nobody is entirely settled on what it is.
The numbers
- What it is
- The Earth crossing a trail of dust left by a comet
- Size of a typical grain
- About a grain of sand
- Where it burns up
- 80 to 100 kilometres up
- Speed
- Tens of kilometres per second
- Perseids
- Peaks around 12 August
- Geminids
- Peaks around 13 December, the best of the year
- Equipment needed
- None. Your eyes are better than any telescope for this
To find out whether it is up tonight, and when it gets properly dark where you are, see Sky Tonight.