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blackpudd1n

Pudd's Questions On Everything Beyond The Atmosphere

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Okay, help me out here guys- how many planets are there? This morning I thought that there was 9, then when I was reading the God Delusion, Dawkins said there was now a tenth planet, unofficially called Xena, then when I was talking in about it in another topic, Ouro said that there was 8, and that we had dwarf planets... I'm confused.

 

Could I look this up on Google? Well, yeah, I could, but as I always seem to lead to more questions, and I get a bit (okay, a lot) fuddled by Science, I thought I'd start a thread on the topic, because I'm sure that more questions will arise in the course of talking about the planets.

 

Also, what is the difference between a sun, a star, a planet, and a dwarf planet? How do they work out how to categorise each? (See, I've already started on more questions!)

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Xena is now officially known as Eris. Here's a good article on it:

 

http://www.scienceda...60914155305.htm

 

I don't know the definition of a planet verses a dwarf planet (like Eris and Pluto), but I think it has to do with size. I think the issue is what "rocks" do we call planets as opposed to other objects like comets, asteroids, etc.

 

I don't think there really is a difference between a sun and a star. Sun is the name we give to the star around which our planet revolves.

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Xena is now officially known as Eris. Here's a good article on it:

 

http://www.scienceda...60914155305.htm

 

I don't know the definition of a planet verses a dwarf planet (like Eris and Pluto), but I think it has to do with size. I think the issue is what "rocks" do we call planets as opposed to other objects like comets, asteroids, etc.

 

I don't think there really is a difference between a sun and a star. Sun is the name we give to the star around which our planet revolves.

 

Quick answer: sun can equal star generically, but our star is officially named the Sun or Sol.

 

Also, the somewhat controversial IAU definition of what a planet is includes the criterion that it has "cleared its orbit of other bodies." This is why Pluto was demoted; since it crosses the orbit of Neptune, this means that it hasn't cleared its neighborhood, but shares its neighborhood with another planetary body.

 

There are also different kinds of dwarf planets. Some are classified as asteroids (such as Ceres); these bodies are made of rock and metal (EDIT: and they are primarily found in the inner solar system). Then there are the trans-Neptunian objects (TNOs) and the Kuiper Belt objects (KBOs), which include Pluto, Eris, Makemake and Haumea, and Quaoar. These are different from the asteroids, because these bodies are made mostly of ice (in astronomy, "ice" refers to any frozen gas or liquid such as methane or ammonia; astronomers will refer to water ice specifically to distinguish it from other kinds of ice). There may be a lot more bodies like Pluto out there, but they are difficult to find for a number of reasons (I can go into more detail about why if you are interested).

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Okay, help me out here guys- how many planets are there?

 

As I understand it (and a quick check of wikipedia didn't contradict me as far as I saw), our own solar system has 8 planets - Mercury, Venus, Earth, Mars Jupiter, Saturn,Uranus, Neptun. Pluto used be classified as planet until a few years ago and has now been "demoted" to the status of dwarf planet.

 

Also, what is the difference between a sun, a star, a planet, and a dwarf planet?

 

Star - a celestial body large enough that its gravitation compresses its core so that nuclear fusion can be maintained.

 

Sun - the star around which our earth orbits. Other than that, sun and star are quite interchangable.

 

Planet - anything that's not a star, is orbiting a star, and is large/heavy enough to have cleared its orbit of debris and pulled itself into a more or less spherical shape.

 

Dwarf planet - anything smaller than a planet (though I'm sure there's some defined limit between dwarf planets and asteroids etc).

 

So, if something has pulled all the small crap that orbited close to it onto itself, and if its large enough to compress itself into a sphere-like shape (in contrast to those asteroids for example which can have pretty much any form... or have a look at the moons of Mars, they are anything but spherical either), it's a planet by the new definition.

 

Oh, just to make matters even more complicated, very large planets that still aren't quite stars are called brown dwarfs. They are just a little bit too small to maintain nuclear fusion in their cores.

 

You can tell that astronomy fascinates me :)

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Just make it more confusing....

 

I read somewhere that if Jupiter had just a bit more mass it would have become a second sun for a few billion years.

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Just make it more confusing....

 

I read somewhere that if Jupiter had just a bit more mass it would have become a second sun for a few billion years.

 

If by "a bit more" they meant more than ten times the mass it has now, which I think is the minimum requirement for temporary deuterium fusion to take place. I'm not sure how bright such a beast would be, since I think most of the energy would still be put out as infrared (heat) and not visible light.

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Xena is now officially known as Eris. Here's a good article on it:

 

http://www.scienceda...60914155305.htm

 

I don't know the definition of a planet verses a dwarf planet (like Eris and Pluto), but I think it has to do with size. I think the issue is what "rocks" do we call planets as opposed to other objects like comets, asteroids, etc.

 

I don't think there really is a difference between a sun and a star. Sun is the name we give to the star around which our planet revolves.

 

Quick answer: sun can equal star generically, but our star is officially named the Sun or Sol.

 

Also, the somewhat controversial IAU definition of what a planet is includes the criterion that it has "cleared its orbit of other bodies." This is why Pluto was demoted; since it crosses the orbit of Neptune, this means that it hasn't cleared its neighborhood, but shares its neighborhood with another planetary body.

 

There are also different kinds of dwarf planets. Some are classified as asteroids (such as Ceres); these bodies are made of rock and metal (EDIT: and they are primarily found in the inner solar system). Then there are the trans-Neptunian objects (TNOs) and the Kuiper Belt objects (KBOs), which include Pluto, Eris, Makemake and Haumea, and Quaoar. These are different from the asteroids, because these bodies are made mostly of ice (in astronomy, "ice" refers to any frozen gas or liquid such as methane or ammonia; astronomers will refer to water ice specifically to distinguish it from other kinds of ice). There may be a lot more bodies like Pluto out there, but they are difficult to find for a number of reasons (I can go into more detail about why if you are interested).

 

Is there a chance those two could ever collide? That would be the astronomical event of the ages for sure.

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Is there a chance those two could ever collide? That would be the astronomical event of the ages for sure.

 

Pluto and Neptune? No. If you find some astronomical software (Starry Night or other equivalents), you can tilt your view of the solar system to see that although the orbits cross from a top view, from a side view they never actually intersect. The actual minimum distance between the two orbits is still quite large (as in, by hundreds of millions of miles, or greater than the distance from Earth to Jupiter). Neptune and Pluto are also in what is called a resonance orbit, so that whenever Pluto is in the portion of its orbit that is closest to Neptune's orbit, the planets themselves are pretty far apart. To get a better idea of how it works, you might want to try the Wikipedia article, which contains more than would be worth typing here.

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Xena is now officially known as Eris. Here's a good article on it:

 

http://www.scienceda...60914155305.htm

 

I don't know the definition of a planet verses a dwarf planet (like Eris and Pluto), but I think it has to do with size. I think the issue is what "rocks" do we call planets as opposed to other objects like comets, asteroids, etc.

 

I don't think there really is a difference between a sun and a star. Sun is the name we give to the star around which our planet revolves.

Here's a wikipedia article on dwarf planets: http://en.wikipedia....ki/Dwarf_planet

 

Thanks for these articles :) I found it interesting that they think that there are many more dwarf planets in our solar system. That makes a lot of sense to me for distinguishing between the bigger and the dwarf planets- otherwise, I reckon that there will be a lot of confused little kids in school, trying to make diaramas.

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There may be a lot more bodies like Pluto out there, but they are difficult to find for a number of reasons (I can go into more detail about why if you are interested).

 

I'm interested :)

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Also, what is the difference between a sun, a star, a planet, and a dwarf planet?

 

Star - a celestial body large enough that its gravitation compresses its core so that nuclear fusion can be maintained.

 

Sun - the star around which our earth orbits. Other than that, sun and star are quite interchangable.

 

Planet - anything that's not a star, is orbiting a star, and is large/heavy enough to have cleared its orbit of debris and pulled itself into a more or less spherical shape.

 

Dwarf planet - anything smaller than a planet (though I'm sure there's some defined limit between dwarf planets and asteroids etc).

 

So, if something has pulled all the small crap that orbited close to it onto itself, and if its large enough to compress itself into a sphere-like shape (in contrast to those asteroids for example which can have pretty much any form... or have a look at the moons of Mars, they are anything but spherical either), it's a planet by the new definition.

 

Oh, just to make matters even more complicated, very large planets that still aren't quite stars are called brown dwarfs. They are just a little bit too small to maintain nuclear fusion in their cores.

 

You can tell that astronomy fascinates me smile.png

 

 

So... How do planets become roundish? Can a planet increase or decrease their mass? Why is every planet made up of different stuff? Was every star and sun once a planet?

 

I can't help wondering how every planet ended up suspended in their particular orbit. How did the planets come to be?

 

You know, this might sound silly, but I still have a little trouble with the concept of the planets and our entire solar system just being suspended in space. It's the sun that keeps them in that spot, right? Its gravitational pull? Its hard for me to understand, because the idea is like a different type of gravity to here on earth. On earth, if it goes up, it comes down again. But in my head the sun's gravitational pull is like sideways or something.

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http://www.csmonitor.com/Science/2011/1209/Are-you-scientifically-literate-Take-our-quiz/Composing-about-78-percent-of-the-air-at-sea-level-what-is-the-most-common-gas-in-the-Earth-s-atmosphere

 

something fun.

 

 

Space has no up or down. There is no where to fall to and nothing to fall into because there is nothing there to pull us down toward it.

 

 

Something that might help with planet evolution.

 

http://www.physics.sjsu.edu/tomley/PlanetEvolution/planetevolution.html

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There may be a lot more bodies like Pluto out there, but they are difficult to find for a number of reasons (I can go into more detail about why if you are interested).

 

I'm interested smile.png

 

Cool. I love talking about this stuff, and I almost never get the chance.

 

The first reason that these things are tricky to find is that they're (duh) far away, and some of them don't reflect as much light back to us as others, depending upon what their surfaces are made of. But that's not all. The farther something's orbit is away from the sun, the more slowly it moves. This means that to find solar system objects that are really far away, you have to look at photographs of a region of space taken some time apart, and see what moves from one picture to the next; the stars in the background won't have moved between the two exposures (because they're really, really far away), but something like a KBO will have moved. Astronomers then use something called a blink comparator to check what has moved between the two exposures (this is now done with the aid of computer, but used to be a monotonous manual process), and after flipping between the before and after shots, they can spot what has moved. As far as I know, almost all of the current crop of KBOs have been discovered using this process.

 

The further away something is, though, the more difficult it is to find by this process, because the object won't have moved much against the background of stars.

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There may be a lot more bodies like Pluto out there, but they are difficult to find for a number of reasons (I can go into more detail about why if you are interested).

 

I'm interested smile.png

 

Cool. I love talking about this stuff, and I almost never get the chance.

 

The first reason that these things are tricky to find is that they're (duh) far away, and some of them don't reflect as much light back to us as others, depending upon what their surfaces are made of. But that's not all. The farther something's orbit is away from the sun, the more slowly it moves. This means that to find solar system objects that are really far away, you have to look at photographs of a region of space taken some time apart, and see what moves from one picture to the next; the stars in the background won't have moved between the two exposures (because they're really, really far away), but something like a KBO will have moved. Astronomers then use something called a blink comparator to check what has moved between the two exposures (this is now done with the aid of computer, but used to be a monotonous manual process), and after flipping between the before and after shots, they can spot what has moved. As far as I know, almost all of the current crop of KBOs have been discovered using this process.

 

The further away something is, though, the more difficult it is to find by this process, because the object won't have moved much against the background of stars.

 

So things just look like stars until they realise that they've moved? How do they take these photographs? And how do they know that we haven't moved, and not the other thing? 'Cause if we're always moving, then it'd be hard to take the picture in the same spot, right?

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A science test??!! This is going to be interesting :/

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A science test??!! This is going to be interesting :/

 

Only 1 right out of 5 so far, and I guessed it :P

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So... How do planets become roundish? Can a planet increase or decrease their mass? Why is every planet made up of different stuff? Was every star and sun once a planet?

 

I can't help wondering how every planet ended up suspended in their particular orbit. How did the planets come to be?

 

You know, this might sound silly, but I still have a little trouble with the concept of the planets and our entire solar system just being suspended in space. It's the sun that keeps them in that spot, right? Its gravitational pull? Its hard for me to understand, because the idea is like a different type of gravity to here on earth. On earth, if it goes up, it comes down again. But in my head the sun's gravitational pull is like sideways or something.

 

That's a lot of questions!

 

How do planets become roundish? Short answer: gravity. At the start of a planet's formation, it accumulates more and more stuff from the nebula from which it forms. As the gravity of the body increases, it pulls that material in tighter and tighter in all directions, which means that the shape becomes spherical.

 

Can a planet increase or decrease their mass? A planet can increase its mass only if it smacks into something else. There isn't really any way for a planet to decrease in mass, unless it's a gas giant that's too close to its parent star and it boils its atmosphere away (we've actually found at least one example of this in another planetary system).

 

Why is every planet made up of different stuff? Good question. We don't have all of the answers for that yet, but there are some hypotheses. Maybe that means that all of science is wrong and the creationists are right! Okay, so maybe not.

 

Was every star and sun once a planet? No. If not enough material is collected in one place, then you wind up with a planet or a brown dwarf; if enough material collects in one place, you wind up with a star.

 

How did the planets come to be? When a mommy star and a daddy star love each other very much... Actually, that's kind of a long story, and you kind of have to go to the beginning of the universe. After the big bang occurred, there was only hydrogen and helium in the universe, which because of gravity coalesced into galaxies, and in the denser parts of the galaxies, the first stars formed. A lot of these stars were huge, and fused a lot of the other elements together from the original hydrogen and helium (another long story); once these stars went supernova (exploded), they blew all of the elements that made up the next generation of stars and planets into their surroundings. From the nebulae that were now enriched with all of these other elements, the next generation of stars formed, and with them the planets. The areas around the new stars first collapsed into giant disks of stuff swirling around (due to the spin of the region and centrifugal force; think soft clay on a pottery wheel), and later the planets started to form as bits of matter clumped with other bits of matter, which then attracted more bits of matter, and then the clumps started to smack into each other to make bigger clumps, and so on. As the planets formed, they swept up more and more of the stuff around them; the bigger planets, such as Jupiter, were large enough to hold onto all of the lighter gases in their atmosphere, while smaller planets could only hold onto some of the heavier gases, and other planets like Mercury didn't manage to hold onto an atmosphere at all.

 

I can't help wondering how every planet ended up suspended in their particular orbit. There may have been a lot of other planets in the early solar system that, due to gravitational interactions, got flung out of the solar system entirely, and some of them just collided with each other. For example, our moon is most likely the result of debris from the collision of the early earth colliding with a Mars-sized body. The orbits of the planets just happen to be where everything settled out after the first few million years or so.

 

You know, this might sound silly, but I still have a little trouble with the concept of the planets and our entire solar system just being suspended in space. It's the sun that keeps them in that spot, right? Its gravitational pull? Gravity works in all directions simultaneously, so there is no actual "up" or "down." However, you can think of objects that orbit other objects as continuously "falling." Any object orbiting another is essentially falling toward that object, but missing it; since there is no medium (such as air) to slow the falling object, it never actually hits the object its falling towards. That's not 100% technically accurate, but it's a way to think about it, at least.

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So things just look like stars until they realise that they've moved? How do they take these photographs? And how do they know that we haven't moved, and not the other thing? 'Cause if we're always moving, then it'd be hard to take the picture in the same spot, right?

 

So things just look like stars until they realise that they've moved? Yes.

 

How do they take these photographs? Pretty much exactly how you would think: a camera (or light-sensitive CCD plate, like a big digital camera) hooked up to the end of a big-ass telescope.

 

And how do they know that we haven't moved, and not the other thing? They compensate for the motion of the earth around the sun and the rotation of the earth when they take the photographs to make sure that the stars in each exposure are in the same spot.

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A science test??!! This is going to be interesting :/

 

Only 1 right out of 5 so far, and I guessed it tongue.png

 

not to worry I got a 78% because I haven't studied some of the equations is like 15 years.

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A science test??!! This is going to be interesting :/

 

Only 1 right out of 5 so far, and I guessed it tongue.png

 

not to worry I got a 78% because I haven't studied some of the equations is like 15 years.

 

...I got 44%. Of the 22 questions I did get right, I only actually knew the answers to 8- the rest were just lucky guesses blush.png

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Something that might help with planet evolution.

 

http://www.physics.s...tevolution.html

 

Wow, that was pretty cool! :)

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Yeah it is. It takes everything Trapped explained and shows it to you.

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So... How do planets become roundish? Can a planet increase or decrease their mass? Why is every planet made up of different stuff? Was every star and sun once a planet?

 

I can't help wondering how every planet ended up suspended in their particular orbit. How did the planets come to be?

 

You know, this might sound silly, but I still have a little trouble with the concept of the planets and our entire solar system just being suspended in space. It's the sun that keeps them in that spot, right? Its gravitational pull? Its hard for me to understand, because the idea is like a different type of gravity to here on earth. On earth, if it goes up, it comes down again. But in my head the sun's gravitational pull is like sideways or something.

 

Ooh, that sounds like story time! I like telling stories! Here's my very rough story about how this stuff works. Hopefully I won't get too much wrong.

 

One upon a time, a long long time ago, the universe was compressed into a small area. It wasn't just the matter of the universe, but all the energy too, so everything was really, really hot. It was so hot that matter as we know it could not exist, since it would be ripped apart by the immense energies. But as the universe expanded, things cooled down enough that matter as we know it could start to form. As this happened, matter also started to clump. So you've got some of the lightest elements from the periodic table starting to form (it's finally cool enough for 'em to stick together) and gather in lumps, pulled together by their own gravity. But it's still crazy hot, and gravity means that in the densest areas the new matter is all running into each other and more hot than elsewhere. This is how the first stars formed. Since it was so hot and dense in the middle of them, the little atoms started to fuze to make bigger atoms. When they do that, they release a lot of energy....

 

Bunny trail! I'm going to explain activation energy because it will make stars make more sense. I'm not sure if this is the right term outside of chemistry, but the concept is the same. So, there are a lot of processes in nature that release tons of energy. But they don't happen very often because they need to have enough energy to start the process before they can get to the point of releasing all the energy. Think of it like trying to get up off the couch on a lazy day; you know if you can just get that tiny bit of energy together to get up, you'll find yourself feeling more energetic and will get all sorts of things done that require a whole lot more energy than just getting off the couch. But you can't get off the couch in the first place. "Activation energy" is the energy required to get off the couch in the first place. Or maybe think about a pile of rocks on a hillside. If they start rolling, there's going to be a huge avalanche. But they're not going to go anywhere until one little pebble starts rolling, hits a bigger pebble, that pebble hits a bigger rock, etc. Getting that first little pebble bouncing down the side of the mountain is the activation energy.

 

Anyway, back to stars. Normally, atoms don't fuse (we do have fission nuclear reactors that rip big atoms apart, but haven't managed to make any usable fusion reactors that combine little atoms into bigger atoms), but with all that energy around in the early stars, they were doing plenty of that. Now, the activation energy required to start the process is pretty big, but the energy released is also huge. That's why stars give off light; that light is some of the energy given off as light elements fuze into bigger elements.

 

Eventually, a star runs out of fuel. The different classes of stars are all about what kind of fuel they're burning right now, and how much energy they have left at the end determines what kind of star they will become next. Some stars explode at the end of their life, flinging the heavy elements they've been making out into space. Some stars are still so hot when they burn up their first round of fuel that they can start "burning" the next set of elements, which are heavier than the first ones. That will make even bigger elements. So all the iron in the earth's core? That's a somewhat heavy element, and was only formed after many rounds of a star doing nuclear fusion. All the carbon that we're made out of? That came from a star, too.

 

So, the planets. Stars have all this matter, and they don't just get rid of it when they die. Stars are pretty violent, and they puke a lot. That's why there's so much dust in the universe. If there's a lot of dust, the gravity of the dust itself will make it start clumping, kinda like giant dust bunnies. Once enough matter clumps like that, it's got a decent bit of gravity and can attract more dust. That's one way for planets to form. Sometimes a hot young start will puke out matter from one stage of nuclear fusion, then continue to burn for a good long time at the next stage of fusion with bigger elements. All that matter that got puked out hangs around the star because the star has a lot of gravity. Eventually the star puke will clump up and maybe form planets.

 

Planets have a lot less mass than the stars they orbit. That's why we say a planet orbits a star. In a binary star system, two stars may be orbiting each other. We consider two stars to be orbiting each other equally because they'll have a similar mass. When a planet orbits a star, the star and planet are actually orbiting each other. But since planets are so tiny compared to stars that the star affects the planets a whole lot more than the planets affect the star, so it's easy to think of it as a fixed star that the planets are circling, and call that a solar system. But then you've got things even bigger (er, more massive; they might be so massive and compact that they're actually small) than stars - black holes. A black hole is so big that entire solar systems orbit them (you can think of it as stars orbiting the black hole, and the stars drag their little planets along for the ride) in the same way a planet orbits a star.

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Just make it more confusing....

 

I read somewhere that if Jupiter had just a bit more mass it would have become a second sun for a few billion years.

 

If by "a bit more" they meant more than ten times the mass it has now, which I think is the minimum requirement for temporary deuterium fusion to take place. I'm not sure how bright such a beast would be, since I think most of the energy would still be put out as infrared (heat) and not visible light.

 

The bad astronomer has to say on that one:

 

"...it turns out there is a lower limit to that mass; if you don't have enough, then you don't get the high temperatures and pressures necessary to ignite fusion. That mass is about 0.077 times the mass of the Sun, or 80 times Jupiter's mass. In other words, Jupiter is 1/80th the mass it needs to turn into a star. Some people call Jupiter a failed star, but in reality it ain't even close."

 

(Source: http://www.badastronomy.com/bad/misc/jupiter_galileo.html)

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