Asteroid

If the shower meteors come from comets, isn’t it likely that the meteorites come from comets too?

Comets

Comet. Image courtesy of NASA.

Many comets exist. Approximately 12 are discovered each year, mainly by amateurs. Several hundred billion are estimated to exist.

Comets have very elliptical (elongated, not round) orbits. It takes comets varying lengths of time to orbit the sun. Some have fairly short periodicities (3 years) and others have periodicities of hundreds of thousands of years. For example, Halley’s comet returns every 76 years. It was first seen in 240 BC by the Chinese.

Millions of comets are believed to form a roughly spherical cloud (called the oort cloud) beyond the orbit of Pluto, at a distance of about 100,000 AU, nearly half the distance to the nearest star. (Pluto’s orbit is at about 40 AU, varying from 29.7 to 49.2 AU.)
Comets tend to be small (several km in diameter). For example Halley’s comet is 16 x 8 km.

Essentially large dirty snowballs, composed of a porous mixture of frozen gases, rocky and metallic material:

water ice (Halley’s comet is 80% water)
carbon dioxide (dry ice)
ammonia
methane
Note: You can make a comet in the classroom with dry ice, ammonia, dirt, etc.

As a comet nears the sun, solar energy vaporizes frozen gases, forming a glowing "head" called a coma.

The comet also develops a tail of ionized gases and dust that may be millions of km long. The tail always points away from the sun, (due to radiation pressure and solar wind) and only follows behind the comet as the comet approaches the sun. As the comet moves away from the sun, the tail preceeds the head.

Comets have no light of their own, but reflect sunlight.
Meteor showers are associated with comets. They occur when the Earth passes through the debris of a (burned out) comet.

******************************************************
Meteors, meteoroids, and meteorites
Meteor = shooting star.
Glow of small particles being heated as they enter the atmosphere.
Can see 6 – 60 per hour.
Meteorites = rocks that reach the earth’s surface from space.

Meteoroid = the object before it enters the Earth’s atmosphere. Most are destroyed by about 80 km above the earth’s surface.

Fireballs = very bright meteors with trains that last up to 30 minutes.

Bolide = Fireball that breaks up on atmospheric entry.
Possible source of CO2?

Comets lose some mass every time they get close enough to a star to leave a tail. Sooner or later it would have to become too small to leave a tail anymore, and sooner or later it would have to disappear completely. I’d imagine the chances of this event actually being observed would be astronomical. Has it ever been known to happen at any time other than when a comet actually gets caught up in our atmosphere?

You are assuming that all the material in the comet head can be vaporized by heat from the Sun at the closest distance the comet gets. But comets are not like that. They have been described as dirty snowballs, and after all the snow is vaporized the dirt is still left. So the comet becomes an asteroid in a very eccentric orbit. It can no longer form a tail but it doesn’t vanish completely. It may really hard to spot without any vapor cloud around it, but it is not completely gone.

What is the chemical composition of comets? Are comets more similar to the inner or outer planets? pleasee helpp!

Parts of a comet

The nucleus of a comet is a ball of ice and rocky dust particles that resembles a dirty snowball. The ice consists mainly of frozen water but may include other frozen substances, such as ammonia, carbon dioxide, carbon monoxide, and methane. Scientists believe the nucleus of some comets may be fragile because several comets have split apart for no apparent reason.

As a comet nears the inner solar system, heat from the sun vaporizes some of the ice on the surface of the nucleus, spewing gas and dust particles into space. This gas and dust forms the comet’s coma. Radiation from the sun pushes dust particles away from the coma. These particles form a tail called the dust tail. At the same time, the solar wind — that is, the flow of high-speed electrically charged particles from the sun-converts some of the comet’s gases into ions (charged particles). These ions also stream away from the coma, forming an ion tail. Because comet tails are pushed by solar radiation and the solar wind, they always point away from the sun.

Most comets are thought to have a nucleus that measures about 10 miles (16 kilometers) or less across. Some comas can reach diameters of nearly 1 million miles (1.6 million kilometers). Some tails extend to distances of 100 million miles (160 million kilometers).

1. They have longer Type II tails than short period comets.
2. Their orbits have random inclinations with respect to the ecliptic plane.
3. Their orbits are nearly circular.
4. They tend to appear larger in diameter than short period comets.

2
The Kuiper belt is mostly in the ecliptic plane. The Oort cloud is a cloud all around the solar system. So comets that have little inclination to the plane are assumed to be Kuiper belts objects and comets with some strange inclination are assumed to be Oort cloud objects.

My uncle has a 1500 gallon pond and has 6 comets and 3 koi in it and a bunch of really small fry. Is this overstocked?

I am also planning to give him 1 koi and 2 comets because I don’t have enough tank space to keep them in, if it is alright.

Tentatively: No, it is not overstocked, and it can accept those additional fish easily. But please keep reading.

In an aquarium, people tend to consider that 20 gallons minimum and a total ratio of 1 goldfish (common) per 10 gallons is safe. That’s assuming 12" to 22" deep. For a pond, it really depends on the depth – deeper ponds will hold fewer fish, since surface area is crucial.

Furthermore, the climate and filtration are important. The warmer the climate (and less shade the pond gets), the fewer fish. In a windy area, more fish can be supported. The less aeration and water movement, the fewer fish. Filter capacity in ponds is also typically not very good unless the person is an enthusiast who built a massive custom oystershell/lava rock/trash can filter, for example.

However, ponds have the advantage of massive algae growth. Algae is somewhat beneficial, since it absorbs waste. Floating plants like water hyacinths are excellent for cleaning ponds (of waste compounds like nitrate, nitrite, and ammonia).

If conditions are ideal – strong filtration, shallow (20" or less), decent water movement (say, 4000 gph), and a cool, windy climate, with lots of floating plants… you could probably stock 50 goldfish with no problems. In a hot, windless area with little shade, no floating plants, no filtration, no bubblers, no forced water movement, and no water changes… I’m not sure. 4 koi and 8 comets might be close to the limit. For koi to goldfish equivalence, I would assume 1" inch of koi is similar to 4" or so of goldfish.