History UsefulNotes / TheSolarSystem

14th Apr '16 4:25:04 PM SSJMagus
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** [[http://en.wikipedia.org/wiki/Comet_Halley Halley's Comet]]

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** [[http://en.wikipedia.org/wiki/Comet_Halley Halley's Comet]]Comet]]: The best-known of all comets, because it's large enough to be seen from Earth and (unlike most large-ish comets) has an orbital period short and predictable enough that the average human has at least one opportunity in their lifetime to see it.


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** [[https://en.wikipedia.org/wiki/90377_Sedna Sedna]]: Almost certainly the sixth dwarf planet. Its orbit is so distant that it never comes within 46 AU of Neptune (which for the record is more than 1.5 times distance between Neptune and the sun) and thus no planet's gravity exerts any influence on it. Its orbit is also extremely elliptical (its closest approach to the sun is 76 AU while the furthest it gets is 936 AU), something that is normally caused by interaction with Neptune and thus causing renewed speculation that a large planet must exist beyond Neptune's orbit. Its orbital period is estimated to be ''11,400 years'', while it's only physically observable from Earth for 25 years of its orbit. This means astronomers were ''very'' lucky to find it.
16th Mar '16 11:51:35 AM AnotherGuy
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You'll often hear, particularly when concerning the ''Voyager'' probes, that they have reached the "edge" of the Solar System; originally this meant moving beyond Pluto's orbit, a definition that now feels very "last century". Now, it generally means when the "atmosphere" generated by the Sun is pushed back by the atmosphere of interstellar space (a point called the heliopause). And while yes, the space beyond the heliopause is technically the same as the space between stars, it is NOWHERE NEAR the edge of the Sun's gravitational influence, which is a thousand times farther out.

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You'll often hear, particularly when concerning the ''Voyager'' probes, that they have reached the "edge" of the Solar System; originally this meant moving beyond Pluto's orbit, a definition that now feels very "last century". Now, it generally means when the "atmosphere" generated by the Sun is pushed back by the atmosphere of interstellar space (a point called the heliopause). And while yes, the space beyond the heliopause is technically the same as the space between stars, it is NOWHERE NEAR the edge of the Sun's gravitational influence, which is a thousand times farther out. \n In fact, the Sun's influence doesn't "end". Rather, it merges with its closest neighbors, including Alpha Centauri. In other words, you're not out of the Solar System til you're in another one.
16th Mar '16 11:48:46 AM AnotherGuy
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The reason behind the introduction of this category of celestial bodies was a discovery of several Kuiper Belt Objects that rivaled or exceeded [[PlutoIsExpendable Pluto]] in size and thus strained the definition of planet. It was decided that it'd be simpler to demote Pluto than to make all of them planets--[[OlderThanTheyThink a similar course of events took place after the discovery of the four largest members of the asteroid belt in the 19th century]]. It, rather expectedly, ended in a massive FlameWar among not just enthusiasts of astronomy, but astronomers themselves. For this reason, one of the planets that precipitated the kerfuffle was appropriately named for Eris, the goddess of discord.

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The reason behind the introduction of this category of celestial bodies was a discovery of several Kuiper Belt Objects that rivaled or exceeded [[PlutoIsExpendable Pluto]] in size and thus strained the definition of planet. It was decided that it'd be simpler to demote Pluto than to make all of them planets--[[OlderThanTheyThink a similar course of events took place after the discovery of the four largest members of the asteroid belt in the 19th century]]. It, rather expectedly, ended in a massive FlameWar among not just enthusiasts of astronomy, but astronomers themselves. For this reason, one of the planets that precipitated the kerfuffle was appropriately named for Eris, the goddess Goddess of discord.
Discord.[[note]]Mike Brown deliberately named it that knowing that by asking the International Astronomical Union to officially declare it a planet would cause a ''lot'' of discord.[[/note]]
16th Mar '16 11:45:09 AM AnotherGuy
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To be completely fair, Pluto is still a "planet" and the arguing over that point is really amounts to more of a FandomRivalry than any serious bickering. Pluto is a '''dwarf ''planet''''' - the word "planet" is right there in the name. Some people exclude it from lists of planets, while others hold onto it as a "Traditional" planet (We did call it a planet for 70 years, after all). Yes, the definitions were in dire need of an overhaul, but everyone still agrees that it's a body in our solar system worthy of study. The fact that all the astronomers responsible for its "demotion" were all eagerly watching the imagery coming in from the New Horizons probe in 2015 is proof of this - absolutely ''none'' of those them was thinking "Well, Pluto's not really a planet, so this whole mission is a pointless wash." So when you hear people arguing over planet/not planet just take it on the same level as "Franchise/StarTrek vs Franchise/StarWars", or "[[Series/MysteryScienceTheater3000 Joel vs Mike]]".

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To be completely fair, Pluto is still a "planet" and the arguing over that point is really amounts to more of a FandomRivalry than any serious bickering. Pluto is a '''dwarf ''planet''''' - the word "planet" is right there in the name. Some people exclude it from lists of planets, while others hold onto it as a "Traditional" planet (We did call it a planet for 70 years, after all). Yes, the definitions were in dire need of an overhaul, but everyone still agrees that it's a body in our solar system worthy of study. The fact that all the astronomers responsible for its "demotion" were all eagerly watching the imagery coming in from the New Horizons probe in 2015 is proof of this - absolutely ''none'' of those them was thinking "Well, Pluto's not really a planet, so this whole mission is a pointless wash." So when you hear people arguing over planet/not planet just take it on the same level as "Franchise/StarTrek vs Franchise/StarWars", or "[[Series/MysteryScienceTheater3000 Joel vs Mike]]".
Mike]]". Some just call it a "world", a nice neutral term for large bodies.
13th Mar '16 3:56:08 PM FordPrefect
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To qualify as a dwarf planet, or "plutino", the object must be big enough that its own gravity has pulled it into a more-or-less round shape. (It also can't be orbiting another planet, since then it would be a moon.) Even beyond the Pluto issue, the concept of dwarf planets is controversial among astronomers because of both the relatively arbitrary distinction between a dwarf planet and a planet[[note]]By some interpretations, ''Neptune'', the third largest planet, would not fit the new definition of a planet, since it has failed to sweep objects such as Pluto and Eris out of its orbit. However, this is a misunderstanding of the term; "Clearing the Neighborhood" also accounts for smaller bodies being locked into an orbital resonance where the are still controlled by the planet without directly orbiting it, which is exactly what Neptune did to everything that it did not expel or capture, Pluto included.[[/note]], and because the terminology is inconsistent (i.e. a dwarf star is ''always'' a ''type'' of star rather than a separate category, so how would a dwarf planet not be type of planet?).

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To qualify as a dwarf planet, or "plutino", the object must be big enough that its own gravity has pulled it into a more-or-less round shape. (It also can't be orbiting another planet, since then it would be a moon.) Even beyond the Pluto issue, the concept of dwarf planets is controversial among astronomers because of both the relatively arbitrary distinction between a dwarf planet and a planet[[note]]By some interpretations, ''Neptune'', the third largest planet, would not fit the new definition of a planet, since it has failed to sweep objects such as Pluto and Eris out of its orbit. However, this is a misunderstanding of the term; "Clearing the Neighborhood" also accounts for smaller bodies being locked into an orbital resonance where the they are still controlled by the planet without directly orbiting it, which is exactly what Neptune did to everything that it did not expel or capture, Pluto included.[[/note]], and because the terminology is inconsistent (i.e. a dwarf star is ''always'' a ''type'' of star rather than a separate category, so how would a dwarf planet not be a type of planet?).
21st Feb '16 8:54:50 AM RainbowPhoenix
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The term "clearing the neighborhood" is the biggest source of confusion to laypeople; even astronomers who support the current definition generally think it's a clunky term and that something like "gravitational dominance" or "dynamic dominance" would be more appropriate. A sufficiently massive object will have three effects on the debris in its orbit. The first is that any objects will be captured and become moons. This is the least likely of the three effects to happen. The second effect, and the one most frequently thought of when people hear "clear the neighborhood" is expulsion: small bodies will be launched into eccentric or out of the solar system entirely. The third, and most frequently misunderstood, is that any small bodies that are not captured or expelled will be locked in an orbital resonance. Neptune and Pluto are a prime example: every time Neptune completes three full revolutions around the sun, Pluto completes two. It was discovered in the 1990s that Pluto is the largest of many objects that were locked into such a relationship with Neptune. Other examples include the Trojan Asteroids that inhabit the regions governed by Earth, Mars, and Jupiter. In short, a small object does not need to directly orbit a major planet to be controlled by its gravity. Where major planets control entire regions, dwarf planets only control their moons at best.

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The term "clearing the neighborhood" is the biggest source of confusion to laypeople; even astronomers who support the current definition generally think it's a clunky term and that something like "gravitational dominance" or "dynamic dominance" would be more appropriate. A sufficiently massive object will have three effects on the debris in its orbit. The first is that any objects will be captured and become moons. This is the least likely of the three effects to happen. The second effect, and the one most frequently thought of when people hear "clear the neighborhood" is expulsion: small bodies will be launched into eccentric orbits or out of the solar system entirely. The third, and most frequently misunderstood, is that any small bodies that are not captured or expelled will be locked in an orbital resonance. Neptune and Pluto are a prime example: every time Neptune completes three full revolutions around the sun, Pluto completes two. It was discovered in the 1990s that Pluto is the largest of many objects that were locked into such a relationship with Neptune. Other examples include the Trojan Asteroids that inhabit the regions governed by Earth, Mars, and Jupiter. In short, a small object does not need to directly orbit a major planet to be controlled by its gravity. Where major planets control entire regions, dwarf planets only control their moons at best.
21st Feb '16 8:39:10 AM RainbowPhoenix
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To qualify as a dwarf planet, or "plutino", the object must be big enough that its own gravity has pulled it into a more-or-less round shape. (It also can't be orbiting another planet, since then it would be a moon.) Even beyond the Pluto issue, the concept of dwarf planets is controversial among astronomers because of both the relatively arbitrary distinction between a dwarf planet and a planet[[note]]By some interpretations, ''Neptune'', the third largest planet, would not fit the new definition of a planet, since it has failed to sweep objects such as Pluto and Eris out of its orbit. However, this is a misunderstanding of the term; "Clearing the Neighborhood" also accounts for smaller bodies being locked into an orbital resonance where the are still controlled by the planet without directly orbiting it, which is exactly what Neptune did to everything that it did not expel or capture, Pluto included.[[/note]], and because the terminology is inconsistent (i.e. a dwarf star is ''always'' a ''type'' of star rather than a separate category, so how would a dwarf planet not be type of planet?). To date, only 5 dwarf planets are known:

to:

To qualify as a dwarf planet, or "plutino", the object must be big enough that its own gravity has pulled it into a more-or-less round shape. (It also can't be orbiting another planet, since then it would be a moon.) Even beyond the Pluto issue, the concept of dwarf planets is controversial among astronomers because of both the relatively arbitrary distinction between a dwarf planet and a planet[[note]]By some interpretations, ''Neptune'', the third largest planet, would not fit the new definition of a planet, since it has failed to sweep objects such as Pluto and Eris out of its orbit. However, this is a misunderstanding of the term; "Clearing the Neighborhood" also accounts for smaller bodies being locked into an orbital resonance where the are still controlled by the planet without directly orbiting it, which is exactly what Neptune did to everything that it did not expel or capture, Pluto included.[[/note]], and because the terminology is inconsistent (i.e. a dwarf star is ''always'' a ''type'' of star rather than a separate category, so how would a dwarf planet not be type of planet?).

The term "clearing the neighborhood" is the biggest source of confusion to laypeople; even astronomers who support the current definition generally think it's a clunky term and that something like "gravitational dominance" or "dynamic dominance" would be more appropriate. A sufficiently massive object will have three effects on the debris in its orbit. The first is that any objects will be captured and become moons. This is the least likely of the three effects to happen. The second effect, and the one most frequently thought of when people hear "clear the neighborhood" is expulsion: small bodies will be launched into eccentric or out of the solar system entirely. The third, and most frequently misunderstood, is that any small bodies that are not captured or expelled will be locked in an orbital resonance. Neptune and Pluto are a prime example: every time Neptune completes three full revolutions around the sun, Pluto completes two. It was discovered in the 1990s that Pluto is the largest of many objects that were locked into such a relationship with Neptune. Other examples include the Trojan Asteroids that inhabit the regions governed by Earth, Mars, and Jupiter. In short, a small object does not need to directly orbit a major planet to be controlled by its gravity. Where major planets control entire regions, dwarf planets only control their moons at best.

To date, only 5 dwarf planets are known:
known, with another forty or so pending confirmation:
20th Feb '16 7:31:41 AM pittsburghmuggle
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Despite years and years of ScienceFiction stories about planets around other suns, we actually lacked any real scientific proof of them until the early 1990's when exoplanets were first detected by their wobble on their parent star. One of the theories for exampleon the formation of our solar system, "Tidal Theory" - 1917, was that a passing star came close to our sun, drawing a filament of solar matter out of it which coalesced into the planets. Website/{{Wikipedia}} has a page on those theories [[https://en.wikipedia.org/wiki/History_of_Solar_System_formation_and_evolution_hypotheses here]] if you are interested.

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Despite years and years of ScienceFiction stories about planets around other suns, we actually lacked any real scientific proof of them until the early 1990's when exoplanets were first detected by their wobble on their parent star. One of the theories for exampleon Until then, it was quite possible that our solar system was simply a fluke. For example, one theory on the formation of our solar system, "Tidal Theory" - 1917, was that a passing star came close to our sun, drawing a filament of solar matter out of it which coalesced into the planets. Website/{{Wikipedia}} has a page on those theories [[https://en.wikipedia.org/wiki/History_of_Solar_System_formation_and_evolution_hypotheses here]] if you are interested.
20th Feb '16 7:30:10 AM pittsburghmuggle
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Despite years and years of ScienceFiction stories about planets around other suns, we actually lacked any real scientific proof of them until the early 1990's when exoplanets were first detected by their wobble on their parent star. One of the theories for exampleon the formation of our solar system, "Tidal Theory" - 1917, was that a passing star came close to our sun, drawing a filament of solar matter out of it which coalesced into the planets. Website/{{Wikipedia}} has a page on those theories [[https://en.wikipedia.org/wiki/History_of_Solar_System_formation_and_evolution_hypotheses here]] if you are interested.
20th Feb '16 7:18:39 AM pittsburghmuggle
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'''Mars''' is red, And '''Jupiter''''s big. '''Saturn''' shows off it's rings. '''Uranus''' is built on a funny tilt, And '''Neptune''' is it's twin.\\

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'''Mars''' is red, And '''Jupiter''''s big. '''Saturn''' shows off it's rings. '''Uranus''' is built on a funny tilt, And '''Neptune''' is it's its twin.\\
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