Why do particles from a comet that result in meteor showers spread out mostly along the comet's orbit? My understanding of the meteor showers that repeat yearly is that the Earth passes through the orbit of a comet that is nowhere near us, and might not even exist anymore, yet it's orbit is filled with a stream of dust in the same heliocentric orbit by way ahead of or behind their cometary source by tens of millions of kilometers or more.

How do these particles spread out along the comet's orbit so far and yet remain tightly correlated transverse to the orbit? Some meteor showers like the "Unicorn shower" linked below can be quite short, lasting only a fraction of a day!


What makes some meteor showers continue for days, while the &quot;Unicorn shower&quot; can be shorter than one hour?
Meteor shower predicted to be best viewed BEFORE midnight (for reasons other than the moon)?
Why are these objects moving at Vastly Different Speeds along the same orbit?


Left: From What (actually) is Jupiter doing to this year&#39;s Perseids meteor shower? Right: From Why would the Perseids meteor rate fall off after maximum faster than the increase before maximum? - click each for full size
The cometary particles need not retain the exact same orbit as the comet in order to stay close together near perihelion, thus where their orbit passes Earth's orbit.

Slight changes in the orbital parameters of the released dust particles can include slighly higher or lower aphelion, and thus change the revolution time and the time of perihelion (Earth) passage enough to spread out the particles. Over many revolutions it will eventually spread out over the whole orbit.

Additionally the orbits by the dust particles are subject to changes due to interaction with the solar wind and solar radiation which will over time change their orbits (yorp effect, Yarkovsky effect, radiation pressure etc).

This behaviour also explains that the meteor showers will be stronger in some years when Earth passes through a part where particles have not yet had time to more equally disperse.

Addendum: The other question on tails How can comets have tails if there&#39;s no air resistance in space? is related. Yet the (visible) tails are caused by either (ionized) gas or (small) dust particles (nm ... µm) which scatter the light. While these dust particles certainly also can make meteors, the larger the particles are, the less efficiently radiation pressure works on them, so their orbital evolution is much slower. And comets do release also a lot of bigger particles from µm up to cm (excact size distriubtion subject to disussion and analysis especially as follow-up to Rosetta mission, also depending on comet size and age) which are not easily visible in the visible light when observing it from Earth.