I Stars, Planets and Satellites

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In solar system, we have sun and planets revolving around it. We have satellites orbiting around some of planets.
Are all of these are same thing, just differentiated on the basis of size and nuclear processes occurring inside them? I mean, if nuclear processes occurring inside their core its a star otherwise its a planet.
If two bodies are revolving around each other and nuclear reactions occurring inside their core its binary system of stars. If one of them has nuclear burning process and other has not, then, it is a star with planet. If both bodies are without nuclear processes they are planet satellite system or something else.
 
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The classification of astronomical objects is far more complex. Mass and chemical composition are much more important parameters. The size (radius) and "nuclear processes" are just consequence of the first two and might be tricky to use them as classification criteria.
For example, white dwarfs have sizes comparable to size of Earth, neutron stars even smaller. Generally, inside white dwarf or neutron star, there is no nuclear fusion occurring anymore and even though they are classified like stars.
Other example, inside Earth's core, there is nuclear process occurring - radioactive decay of some unstable isotopes like uranium. Even though we don't classify our planet as star.
 
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The classification of astronomical objects is far more complex. Mass and chemical composition are much more important parameters. The size (radius) and "nuclear processes" are just consequence of the first two and might be tricky to use them as classification criteria.
For example, white dwarfs have sizes comparable to size of Earth, neutron stars even smaller. Generally, inside white dwarf or neutron star, there is no nuclear fusion occurring anymore and even though they are classified like stars.
Other example, inside Earth's core, there is nuclear process occurring - radioactive decay of some unstable isotopes like uranium. Even though we don't classify our planet as star.
Ok, then how to classify them ?
 
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Well, at the most general level, I think you can stick with classification as explained here, and ignore the example I used above with degenerate remnants of stars (whit dwarf and neutron star). The goal of that example was just to show that size and nuclear processes cannot alone be used as criteria. (All main sequence stars do burn hydrogen in a nuclear fusion process). When you want go into more details, this link might be helpful:
https://en.wikipedia.org/wiki/Astronomical_object
 

sophiecentaur

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Ok, then how to classify them ?
Based broadly on the composition and the processes involved. But never too slavishly as to lose the overall picture. Once you get into the train spotting mentality, the understanding starts to go out of the window. When they decided to reclassify Pluto, you'd think its orbit and mass had changed, if you read the comments in the press.
 

Janus

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When they decided to reclassify Pluto, you'd think its orbit and mass had changed, if you read the comments in the press.
In a way, its size/mass had changed (or at least the estimation of its size/mass). The roots of its demotion to non-planet status began with the discovery of Charon in 1978. Prior to that, astronomers thought they were looking at a single object rather than a pair. This caused them to overestimate the size and mass of Pluto. I have an astronomers handbook from 1974 that lists Pluto's diameter as 3600? miles. This puts it about halfway between Mercury and Mars in size. It now has a known diameter of ~1500 mi, 41% that of the earlier estimate or just a little more than 1/2 that of Mercury.
 

sophiecentaur

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In a way, its size/mass had changed (or at least the estimation of its size/mass).
My point was that there is more to Astronomy than lists. I never was one for collecting bus or train numbers and I don't remember a single cricket of football score so perhaps I'm a bit biassed about 'info for the sake of info'.
 

stefan r

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Ok, then how to classify them ?
It becomes more simple if you talk to an overworked/underpaid elementary school teacher who is at most slightly interested in astronomy and would never consider something like building a telescope. (S)He needs core information to present in a class. The teacher will be embarrassed if someone points out that information stated in class is incorrect. The students will suffer if they later take a test and are told they are wrong. If students learn correct information outside of class that extra knowledge should never cause them to get lower grades in classes.

They need to know 8 "planet" names. Half(4) are rocky. The other half are gassy(2) and icy(2). 2 planets are "inside" of earth. Mars and Earth are the 2 rocky planets further out. The gassy planets have a spot or a big ring and they have stripes. Even NASA says the icy planets look boring and you can not see them without a telescope. They should also know that there is an asteroid belt and that makes a nice dividing line between the rocky planets and gassy planets. Everything is in pairs so there are also comets. In the northern hemisphere you should be able to find Orion and the Big dipper. You can use the big dipper to find Polaris and avoid staying lost for more than a few days (do not get lost in Australia, crocodiles and emu). Airplanes blink, satellites normally do not. Both move while you watch. Planets move around slightly night to night and might be gone for a few months. Constellations cycle and will repeat every year which is one way to tell when vacation starts. Ptolemy lived in Africa and the Chinese imperial court kept lots of records of comets.

If elementary students are interested in Ceres and Sedna there is no reason to discourage them. Make sure there is an astronomy book in the library. Astronomy clubs often have programs for children and some are interesting for parents too. Field trips to a planetarium are great.

In biology it helps to be able to recognize an animal and place it in a class. The platypus is interesting and it is real but that does not make "mammal" a bad category. When you are out hiking it is usually easy to recognize if something is a mammal or a bird. Elementary school graduates should be able to see pictures of a bull frog, a robin, and a cat and be able to match them with the words mammal, amphibian, and bird. Including a picture of a platypus hatching out of an egg might be somewhat unfair.
 
The classification of astronomical objects is far more complex. Mass and chemical composition are much more important parameters. The size (radius) and "nuclear processes" are just consequence of the first two and might be tricky to use them as classification criteria.
For example, white dwarfs have sizes comparable to size of Earth, neutron stars even smaller. Generally, inside white dwarf or neutron star, there is no nuclear fusion occurring anymore and even though they are classified like stars.
Other example, inside Earth's core, there is nuclear process occurring - radioactive decay of some unstable isotopes like uranium. Even though we don't classify our planet as star.
inside Earth's core, there is nuclear process occurring - radioactive decay of some unstable isotopes like uranium. Even though we don't classify our planet as star.
The decay of certain elements, e.g. uranium and thorium, through the spalling off of alpha and beta particles with associated gamma radiation, occurs in the Earth's crust, producing radiogenic heat. I'm not aware that this process is known to occur deeper in the mantle or core, but perhaps it does. This nuclear process involving fission, or splitting, is however totally different from the fusion of hydrogen into helium that takes place in the cores of stars, such as the Sun.
 
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The decay of certain elements, e.g. uranium and thorium, through the spalling off of alpha and beta particles with associated gamma radiation, occurs in the Earth's crust, producing radiogenic heat. I'm not aware that this process is known to occur deeper in the mantle or core, but perhaps it does. This nuclear process involving fission, or splitting, is however totally different from the fusion of hydrogen into helium that takes place in the cores of stars, such as the Sun.
I admit, I should have used rather "Earth's interior". I didn't intend to specify any particular layer of the structure of the Earth, so "Earth's core" is just a wrong terminology in this context. Thanks for the correction.

OP was mentioning "nuclear processes" as a criteria in his original post, not specifying fission or fusion. As I mentioned in post #4, all main sequence stars fuse hydrogen into helium, as a primary source of energy.
 

stefan r

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The decay of certain elements, e.g. uranium and thorium, through the spalling off of alpha and beta particles with associated gamma radiation, occurs in the Earth's crust, producing radiogenic heat. I'm not aware that this process is known to occur deeper in the mantle or core, but perhaps it does. ...
Known to be in the mantle. No samples from the core.
 

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