Why are comets predictable?

Answer 1

Meteor "showers" happen when the Earth passes through the path of an old or extinct comet. As the comet approaches the Sun each pass, the frozen gasses of the nucleus vaporize, and the gas then carries away some dust and sand into space. But it's not pushed very far; the dust and gas are still orbiting the Sun ALMOST in the same orbit as the comet does.

So after a thousand or more orbits, there gets to be a dusty path all the way around the Sun. When the Earth passes through (or near) the dusty path, we get grains of dust and sand striking the Earth, falling into the atmosphere, and burning up - a "shower" of meteors. The path doesn't change; it only intersects the Earth's orbit at one point, and the Earth hits that point just about the same date each year.

And so we get regular "periodic" meteor "showers".

Answer 2

They can be predicted, to some extent. There are well-known showers that occur at certain times of year and which appear to come from a particular constellation.

For example the "Perseids" shower, which comes from the direction of the constellation Perseus. We can't predict how intense a particular will be however.

(The peak intensity of the Perseids is usually around August 12th and 13th.)

Answer 3

Some meteors seem to appear randomly, i.e., it can't be predicted when they come. But many meteors come in groups, and have a specific orbit. It is believed they formed from the disintegration of comets. The meteor showers appear when Earth crosses their orbit.

Answer 4

They aren't, so much. Very few comets are "periodic", in the sense that we've seen them before; Halley's Comet is the classic example, of course.

The vast majority of comets are new; either "periodic" with such a long period that they were last seen in pre-historic times, or hyperbolic comets that will _never_ return to the solar system. And our Sun-watching telescopes have discovered something moderately amazing; over the past few years, there have been dozens of "Sun-diving" comets that have fallen into the Sun, which have been discovered only hours or days prior to their extinction.

Once a comet has been discovered and its orbit calculated, it is a "falling rock". We can predict with some confidence their paths through the solar system. We cannot be perfectly accurate, of course, because gas pocket eruptions on the comet can act like a jet and alter its path, or nearby planets can deflect it.

Answer 5

Once you know the orbit of a comet, it is VERY predictable. The problem is that astronomers have only been making ACCURATE observations of comet positions for about 250 years; before that, the locations, dates - in many cases, even the YEAR - was a matter of some guesswork. And since only fairly short-period comets have been observed more than once for more than about 200 years, it's difficult to calculate their next return.

For "new" comets, things that have never been in the inner solar system (or have done so very few times, or at very long periods) there are NO records of previous apparitions, and so we have no way to predict when they will appear. For example, Comet Hale-Bopp had visited the inner solar system only once before (we believe) and that over 4000 years ago!

So, most comets that we see are not previously recorded; they are new to us.

Answer 6

Meteor showers happen when the Earth passes through (or near) the orbital path of a comet. As the comet orbits the Sun and makes pass after pass by the Sun over thousands of years, the material blown off by the "tail" of the comet eventually spreads to cover the entire orbital path. In some cases, we know what comet it is; in many cases, we can't find the comet and presume that it disintegrated after passing close to the Sun too many times. But the dust lives on!

In a few cases, we've been able to calculate pretty accurately what the orbital path is, and we're able to predict quite well precisely when the shower will peak.

Answer 7

Meteor showers happen when the Earth passes through a cloud of rocks and ice.

This happens at nearly the same time every year. It is simple to predict that the next meteor shower will happen at that same time, again next year.

Answer 8

Like all meteor showers, the Leonids are caused by going through dirtier parts of space, causing dirt to burn up in the atmosphere. Usually it is from passing through the trail of a comet. The Leonids are caused by passing through the tail of Tempel-Tuttle, and it happens each November.

Answer 9

Thousands of old, in many cases extinct, comets circle (or circlED) the Sun over the past few billion years. When a comet has exhausted its ices and volatiles, the rocky dusty remains continue in their orbits.

Over the course of thousands or millions of orbits, the dust cloud of debris blown away from the comet continues, and spreads out; now the trail of dust goes all the way around the Sun. Some of those dust trails come close to, or intersect, the orbit of the Earth.

When the Earth passes through that dust trail, the grains of dust and pebbles streak through the atmosphere as meteors, and we call this a "meteor shower". Since it happens when the Earth passes through the trail at the same point every orbit, it happens at about the same time each year.

Answer 10

Meteor showers occur when the Earth passes through a trail of debris left by a comet.

The Earth hits some of the same trails every year as it orbits the Sun.