total newb question I know, but I've always been curious.

What are the differences? Obviously they're not the same, because they have different names right? -but yet they seem the same....Is it a size and speed difference that separates them into these 3 catagories? I've wondered about this for a long time, and just now finally seeking an answer lol.

 So could someone please explain it to me. thanks

Asteroids are small solar system bodies that are silicate and iron, primarily, and are thought to have formed from the solar nebula about 4.55 to 5 billion years ago, generally in the area between Mars and Jupiter. Those which formed nearer the Sun have impacted the terrestrial planets during the early and late heavy bombardment periods of planet formation more than 1.5 billion years ago.

Asteroids can be any shape and size. Only the largest are roughly spherical, and collisions over billions of years have reduced many of the smaller ones to rubble piles (loosely bound aggregates of material orbiting in "clumps" due to mutual gravitational attraction of the individual pieces).

Meteoroids are smaller bits of asteroids ranging from about the size of a small house down to dust-grain size (the smaller ones are called micrometeoroids) orbiting mostly in the plane of the solar system, from roughly the orbit of Jupiter inward, most of them -- again -- in the vicinity of the Main Belt between Jupiter and Mars. There is no speed classification that separates them from asteroids, so it is mostly a matter of size. Anything up to about 10 meters in diameter (or longest dimension) is normally called a meteoroid and not an asteroid.

Meteors are meteoroids which have entered the astmosphere of a planet. They normally ablate due to frictional heating and glow brightly on their way through the atmosphere. The smallest ones (from about the size of a marble down to the size of sand grains) usually burn up completely in the planet's atmosphere. Larger and smaller ones often make it to the surface of the planet and are called meteorites.

Comets are dirty snowballs, or snowy dirtballs, which are thought to have formed in much the same way as asteroids. However, they formed further out than the terrestrial planets, beyond what is called the "snow line" -- the orbit beyond which liquid water couldn't exist in the solar nebula. There are two known orbital areas for comet formation:

• Short-period comets are thought to have formed in what is called the Kuiper Belt, out to about twice the distance of Pluto.
• Long-period comets are thought to have formed in what is called the Oort Cloud, a football-shaped cloud of perhaps trillions of icy/rocky small solar system bodies orbiting the solar system at distance of several billions of miles.

Short-period comets sometimes are disturbed gravitationally -- either by orbital resonances created by the Gas Giant planets or by passage of another body near the solar system -- and pass inward toward the Sun, where they are often captured in the gravitational wells of Jupiter or the Sun and are sometimes shared between them. Short-period comets are the ones which tend to repeat their passes by the Sun in roughly human-generation time spans or less.

Long-period comets can be disturbed from the Oort Cloud when the solar system passes a nearby star or molecular gas or dust cloud too closely, and fall inward toward the Sun. Since their potential energy is very great they most often are ejected from the solar system in a hyperbolic trajectory after passing the Sun.

Hope that helps ...

The only thing that I'd like to add to Jeff's excellent response is that most of the meteors that are associated with meteor showers (and the rare meteor storm) are streams of debris cast off by comets.

http://ssd.jpl.nasa.gov/?meteor_streams

http://csep10.phys.utk.edu/astr161/lect/meteors/showers.html

http://www.amsmeteors.org/showers.html

http://www.nineplanets.org/meteorites.html

Dave Mitsky

Yep, thanks, Dave!

Here's another thought on the speed question:

• Asteroids appear star-like (that's what the word means), so they don't generally appear to move as you watch them. Exceptions are close passes to Earth, where they move visibly if they're large or bright enough to see directly. So, you would say they're visually "slow, generally not moving as you watch." This is because they're generally far from Earth and not very large.
• Comets likewise do not appear to move much as you watch them. However, with any magnification at all you can sometimes see them move against the starry background. And when they're near to Earth you can notice some movement from night to night. So, you would say they're visually "not very fast, moving little as you watch." This is because they're generally far from Earth and small, except for their tails (which can be millions of miles long).
• Meteors are only visible when they enter the atmosphere, often at cosmic velocities (thousands of kilometers per second!). They move so rapidly they often disappear with a second or two. Even the Earth-grazers which cross the entire sky usually do so in less than a few seconds. So, you would say they're visually "very fast, disappearing as you watch them!" This is because they're generally very small and very nearby (most start to glow about 60 km agove the Earth and burn up entirely within just a few tens of kilometers).

This has nothing to do with official classification, and has little bearing on their actual velocities -- only their apparent visual speeds.

thanks for the information guys. I appreciate it.

 So let me get this straight, and please correct where I'm wrong because I still don't know if I have this down 100% yet or not. First thing is, I shouldn't call them meteors, I should call them meteoroids. They are called meteors only when they hit our atmosphere correct?

Secondly, I get the feeling by reading the information and visiting the websites listed, that really in all actuality, they basically are the SAME THING. Just different small variables such as size and temperature. It seems that meteoroids come from asteroids, and meteors in showers generally fall to the earth from comets passing by. So if 1 = 2, and 1 = 3, that means 3 = 2 which makes them all relatively the same. Basically, I get the feeling that all these scientists labeled the same object different names at various stages of it's life, or the location of it's birth and formation.

Right now the way I see it, asteroids and meteoroids are the same thing, with meteoroids being smaller. Comets are the same composition as asteroids and meteoroids, just much much cooler by birth, completely covered in ice that sometimes melts away and releases meteor particles and dust.

^^^if this is how I explained it to some Joe-schmo, would I be correct?

Almost, but not quite. You only call it a meteorite once it has hit the planet.

The life cycle goes something like this:

1. The presolar nebula was bits of dust and gas, and the occasional interstellar grain.
2. At some point, there was enough of this stuff that it started to collapse gravitationally and to clump (both due to inhomogeneities in the cloud and to static attraction).
3. As bits clumped, the clumps grew and aggregated into chunks, that aggregated into larger pieces, and so on.
4. As the cloud began to spin, more of the denser material aggregated near the center, toward where the Sun would eventually form.
5. Once the Sun lit up, solar radiation pressure forced the lighter elements near the center outward, toward where the Gas Giants formed.
6. After several million years of this, the outer regions cooled sufficiently more than the inner regions that gases became stable and liquid water froze.

Now, throughout this process, little bits grew into bigger bits and some flew outwards while others settled into more stable orbits. There was so much flotsam and jetsam that collisions were frequent and this made the whole system somewhat -- but not entirely -- chaotic. Eventually, the little bits gathered where orbital resonances from the bigger bits wouldn't disturb them. The bigger bits became planets and the smaller bits either:

• collided with each other and created smaller bits (to start the aggregation process anew)
• collided with planets, and merged or vaporized (contributing their materials to the planet if gravity was sufficient to overcome velocity)
• were ejected from the system entirely, due to gravitational perturbances
• settled into orbit around and between planets

After enough time, what was left over is what we see today: some asteroids and meteoroids in the Main Belt, others at Lagrangian points in planetary orbits, and some -- particularly smaller ones -- scattered throughout the system following planetary perturbations.

That's a deliberate oversimplication. But my point in bringing it up is that the gases, silicates and metals present in the presolar nebula (perhaps also enhanced by influx of interstellar materials from nearby supernovae) were the construction materials for everything in our present solar system. The distinctions between them are somewhat arbitrarily based on eventual size. So, the presolar grains that are found in carbonaceous chondrites, for example, are relatively unchanged from 5+ billiion years ago, while the metal in the cores of terrestrial planets -- having come from the same source -- have been recycled as part of the planet-building and evolutionary process.

Therefore, it is somewhat correct to say that asteroids and meteoroids are the same -- or at least very similar except as to size. It is also somewhat correct to say that asteroids and comets are similar (we believe today they're more similar than we did a decade ago, thanks to visits and flybys of spacecraft, some of which have returned materials to Earth for study). But it's only somewhat correct, since comets have a great deal more water and other ices than do asteroids -- presumably a consequence of their having formed further out in the system.

And meteors, though they are the flashy complexions of meteoroids and cometary dust grains, are a wholly different sort of beast in that they are wholly temporary: they only are called meteors while they're in visible flight through a planet's atmosphere (they have been imaged by the Mars ROVER exploratory vehicles in addition to being a common sight in Earth's atmosphere). The solid part of a meteor is made of the same stuff as asteroids and comets, but the label meteor is applied only temporarily. Afterward, they're either meteorites, or vapor.

The word meteor derives from two Greek root words:

• meteoros: high in the air, from meta + eoros, from
• aerein: to lift

A meteoroid may become a meteor and, if it survives passage through the atmosphere, a meteorite when it impacts the planet. After that it may be wholly or partially destroyed, or it may land softly enough to remain intact.

yeah, that was my bad. I meant to say I should call them 'meteoroids' instead of meteors. 

All these names for the same thing it seems, gets confusing at first lol. I'm glad I made this thread though, because before, I would have just called them meteors whether flying thru space, or coming to Earth and impacting the ground. I would have just called them meteors. So now after making this thread, I have learned that the cycle goes like this with the different classifications of names:

 asteroid = huge chunk of nebula debris

meteoroid = smaller chunk of nebula debris

meteor = meteoroid that has entered a planet's atmosphere

meteorite = meteor that has impacted the planets surface

comet = small chunk of nebula debris formed further outward that contains more water and ice than an asteroid

^^^How does that look now if I were explaining it?

.....also, would it be safe to say that a comet is basically a meteroid that contains more water and is really super cold do to it's formation so far out into space?
 

By George, he's got it! (with apologies to Bernard Shaw)

chipdatajeffB:

By George, he's got it! (with apologies to Bernard Shaw)

YES!!!!!!!!!!!! I feel just as excited as Howard Dean in this pic!

 ...or maybe even Al Roker here:

btw, thanks for teaching me this stuff. Now I can start making the other 100 or so threads of stuff that I haven't figured out yet! 

 allright, well I thought I pretty much had this thread on lockdown...but then I got to thinkin'...

 Scientists have recently de-classified Pluto as a planet due to it's lack of size, so does that now officially make Pluto a giant asteroid???

also, would it be safe to say that comets can be the size of an asteroid? can comets get that big in size, or are they generally meteroid sizes?

Killer Rob:

Scientists have recently de-classified Pluto as a planet due to it's lack of size, so does that now officially make Pluto a giant asteroid???

The IAU finally got around to devising a definition for planet. It's not perfect, but it served to classify Pluto as a dwarf planet/small solar system body. Many of us regard it as one among many TNOs: trans-Neptunian Objects. There are several threads here already that talk at length about Pluto's change of classification, so I won't belabor the point. But size is only one of several criteria.

also, would it be safe to say that comets can be the size of an asteroid?

Yes!

can comets get that big in size, or are they generally meteroid sizes?

Yes, they're often quite large. The solid part of the comet is generally frozen gases and water with a good deal of silicate material as well. Gerard Kuiper first described comets as "dirty snowballs," a moniker that stuck well until very recently. We now would call them "snowy dirtballs" since they seem to a have a good deal more silicate material than we'd previously thought.

The Deep Impact probe gave us our first really good look at the interior of a comet, when its impactor created a good-sized crater and astronomers used spectrography to determine the constituent elements of the resulting dust cloud. The surprising result was the much higher percentage of silicate material than had been predicted.

cool...thanks for all the insight Jeff, I appreciate it

ps. cool hummingbird shots on your site there! 

Killer Rob:

ps. cool hummingbird shots on your site there! 

TY! It's been too cloudy for astrophotography this week ...