# What determines if a comet's debris will produce periodic meteor showers?

Astronomy Asked by mihirb on December 31, 2020

Background

I was wondering if the debris from the comet NEOWISE that recently passed Earth would provide meteor showers in the future.

I looked up that the Perseid meteor showers happen when the Earth passes through the debris left behind by comet Swift-Tuttle which has a nucleus diameter of 26 km. In comparison, the comet NEOWISE has a nucleus diameter of 5 km. I am guessing this means it is too small to have a debris trail that produces periodic meteor showers? I was not able to find data about the length of these comets’ tails.

The Question

What determines if the debris from a comet will produce periodic meteor showers in the sky?

After thinking about it a bit myself it seems like these variables should be important:

• Diameter of the comet
• Length of tail when comet reaches Earth’s orbit (which probably depends on comet size and composition)
• Orbit of comet and its relation to Earth’s orbit
• Orientation of comet / comet’s tail in relation to Earth when it crosses the Earth’s orbit
• Whether or not tail extends to Earth as the comet moves farther away from Sun
• Whether or not the debris persists after the comet has left

I was hoping someone could provide more insight into what determines if periodic showers will be produced by a comet. Specifically, what variables are involved (comet size, length of tail, comet’s orbit in relation to Earth’s orbit, etc.). I’m particularly interested in what determines the length of a comet’s tail as well as whether a debris trail persists long after the comet has left.

Meteor showers tend to be formed from dust from short period comets. As they swing repeatedly around the sun, they build up a stream of dust in orbits close to their own orbit. Some will be pushed slightly off the comet's orbit and end up orbiting faster or slower than the comet, and eventually the stream of dust will go all around the sun.

The other thing that there needs to be to get a meteor shower is a comet whose orbit is close to crossing the Earth's orbit. Comet Swift-Tuttle is one such body. Its orbit passes only 130,000 km from the Earths orbit (close enough that there was at one point some concern that it could collide with the Earth in the future. This has now been ruled out for the next two thousand years).

Neowise will release dust, but most of that dust will still be near the comet now and it will continue to orbit with the comet. So that dust will be leaving the inner solar system and will become too spread out to cause a significant meteor shower by the time it returns in several thousand years. Neowise doesn't approach the sun often enough to build up a significant stream of dust particles.

So to summarize it's not really the comet's tail intersecting the Earth's orbit that leads to showers but the debris stream built up along the comet's orbit as it repeatedly goes around the Sun. In long-period comets the debris stream is spread out too much along the orbit to produce a significant stream but short-period comets can produce a significant stream leading to showers.

Correct answer by James K on December 31, 2020