How often to comets appear?

Question

Its for a science thing...

Answer 1

Comets are classified according to their orbital periods. Short-period comets, also called periodic comets, have orbits of less than 200 years, while long-period comets have longer orbits but remain gravitationally bound to the Sun, and main-belt comets orbit within the asteroid belt.[5] Single-apparition comets have parabolic or hyperbolic orbits which will cause them to permanently exit the solar system after passing the Sun once.

early observations have revealed a few genuinely hyperbolic orbits, but no more than could be accounted for by perturbations from Jupiter. If comets pervaded interstellar space, they would be moving with velocities of the same order as the relative velocities of stars near the Sun (a few tens of kilometres per second). If such objects entered the solar system, they would have positive total energies, and would be observed to have genuinely hyperbolic orbits. A rough calculation shows that there might be 4 hyperbolic comets per century, within Jupiter's orbit, give or take one and perhaps two orders of magnitude.

On the other extreme, the short period Comet Encke has an orbit which never places it farther from the Sun than Jupiter. Short-period comets are thought to originate in the Kuiper belt, whereas the source of long-period comets is thought to be the Oort cloud. A variety of mechanisms have been proposed to explain why comets get perturbed into highly elliptical orbits, including close approaches to other stars as the Sun follows its orbit through the Milky Way Galaxy; the Sun's hypothetical companion star Nemesis; or an unknown Planet X[6].

Because of their low masses, and their elliptical orbits which frequently take them close to the giant planets, cometary orbits are often perturbed. Short period comets display a strong tendency for their aphelia to coincide with a giant planet's orbital radius, with the Jupiter family of comets being the largest, as the histogram shows. It is clear that comets coming in from the Oort cloud often have their orbits strongly influenced by the gravity of giant planets as a result of a close encounter. Jupiter is the source of the greatest perturbations, being more than twice as massive as all the other planets combined, in addition to being the swiftest of the giant planets.

A number of periodic comets discovered in earlier decades or previous centuries are now "lost." Their orbits were never known well enough to predict future appearances. However, occasionally a "new" comet will be discovered and upon calculation of its orbit it turns out to be an old "lost" comet. An example is Comet 11P/Tempel-Swift-LINEAR, discovered in 1869 but unobservable after 1908 because of perturbations by Jupiter. It was not found again until accidentally rediscovered by LINEAR in 2001.

Answer 2

If you had a telescope, some comets are visible all the time.

As far as naked eye comets, there are as some above suggest, periodic comets like Halleys, and soemwhere there will be a calendar of those - look up periodic comets on wikipedia.

Then, there are the ones that nobody knows about until they arrive from deep space, like the recent Comet McNaught.

These comets come from way beyond the outer planets, a cloud of trillions of comets called the Oort cloud. Normally they stay out there, but occasionally some gravitational condition (passing star, or passage of Solar System through denser parts of the galactic arm) knocks some out of their normal orbit, and some head for the inner Solar System.

Because nobody can predict these (at present), they come as a complete surprise, and sometimes, as with McNaught, they brighten much more than expected.

The nice thing about these comets is that it is still possible for amateurs to discover them before the pros do. Then you get your name attached to it for ever.

So, go get yourself a super pair of binoculars (25 x 100) and scan that sky.

Answer 3

Comets are not fully understood, however there are some new theories regarding cosmology and the origins and make-up of comets. The standing theory that comets are 'dirty snowballs' is being challenged by cosmologists providing some evidence suggesting that electrical properties of plasma physics shed new light on comets.
For a real mind-bender view the provided video and make up your own mind!

Answer 4

Actually there are several comets in the sky right now that are visible with binoculars or small telescopes. Not all comets are visible to the naked eye. Beautiful, bright comets like the recent McNaught comet are pretty rare.

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Answer 5

Hi. Some are in an obit which brings them back periodically, like Haley's Comet. Most are either very long period comets or fresh from the space way beyond Pluto.

Answer 6

Comets do no longer "come by way of" the image voltaic equipment: all are finished-fledged everlasting contributors of the image voltaic equipment. vivid comets interior the previous few years have secure McNaught, Holmes, and Zhang-Ikeya.