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Thesolar systemis an enormous seat . Our cosmic neighborhood admit eight planets , around half a twelve dwarf planet , several hundred synodic month and trillion of asteroid and comet , all spinning around the sun — and in many cases each other — at amphetamine of one thousand of miles per hour , like a elephantine top .
But where does it terminate ? Well , the answer may depend on whom you ask and how they fix thesolar organisation .
The solar system has three potential boundaries depending on how you define it.
There are not one , but three potential boundaries to the solar organization , according toNASA : the Kuiper Belt , the mob of bouldered bodies beyond the reach ofNeptune ; the heliopause , the edge of the sun ’s magnetic arena ; and the Oort Cloud , a distant source ofcometsthat are scantily seeable from Earth .
The arguments for each bound " all have deservingness , " which makes choosing between them complicated , Dan Reisenfeld , a researcher at Los Alamos National Laboratory in New Mexico , told Live Science in an email .
But there is one that most astronomers most commonly agree upon .
The solar system has three potential boundaries depending on how you define it.
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Kuiper Belt
The Kuiper Belt extend between 30 and 50 astronomical units ( AU ) away fromthe sun , agree toNASA . ( One astronomical unit is equal to the aloofness between Earth and the sun . )
This region is filled with asteroids and gnome satellite , such asPluto , that have been ejected from the inner solar system by one - sided gravitational tugboat - of - war with the satellite .
Some astronomers argue that the Kuiper Belt should be considered the edge of the solar system because it slackly symbolise the edge of where the Sunday ’s protoplanetary disc — the purl anchor ring of gaseous state and dust that later became the satellite , moons and asteroids — would have been .
The Kuiper Belt is mainly made up of asteroids.
" If one narrowly defines the solar system as just the Sunday and its planetary bodies , then the edge of the Kuiper Belt can be think to be the bound of the solar system , " Reisenfeld said .
But this definition of the solar system is count to be far too bare by some astronomers , such as Caltech’sMike Brown .
" It ’s not really true , " Brown tell Live Science in an email . " thing have moved around a lot — mostly outward — since the satellite were form . " This means the Kuiper Belt does not contain all of the solar system of rules ’s " stuff , " such as the elusive , hypotheticalPlanet Nine , which ( if it exists)likely lie far beyond the Kuiper Belt .
The heliopause is the point where solar wind meets interstellar space.
In October 2023 , thediscovery of a dozen new objects beyond the Kuiper Beltalso hinted that there may be a " 2nd Kuiper Belt " lurking even further out .
The uncertainty around this region ’s own out border therefore hold it an unreliable boundary for the solar system as a whole , some researcher argue .
Heliopause
The heliopause is the tabu edge of the sunlight ’s magnetic influence , known as the heliosphere . At this point in time , the stream of charged particles pass off by the sun , known as the solar wind , becomes too weak to rebuff the oncoming stream of irradiation from stars and other cosmic entity in theMilky Way .
" Because the plasma inside the heliopause is of solar origin , and the plasm outside the heliopause is of interstellar stock , some people look at the heliopause to be the boundary of the solar system , " Reisenfeld said . As a result , the space beyond the heliopause is also often cite to as " interstellar space , " or thespace between stars , he sum up .
Two spacecraft have jaunt beyond the heliopause : Voyager 1 , which made the interbreeding in 2012 , and Voyager 2 , which cross over in 2018 . As the Voyager probes crossed the heliopause , they quickly detected changes in the types and levels of magnetism and radiation therapy hit them , mean that they had spoil some sort of border , Brown say .
The Oort Cloud (left) is much larger than the inner solar system (right) or the Kuiper Belt (center).
However , despite its name , the heliosphereis not a pure sphere . Instead , it ismore of an oblong blobbecause most of the interstellar plasma bombarding the solar scheme hit us from one direction , which creates a bow shock — a rounded shock wave that head off incoming radiation around the residual of the solar organization . The prow shock absorber is situate around 120 AU from the sun , and creates a farseeing tail that stretches at least 350 AU from the sun in the polar direction .
Using the heliopause to delineate the solar system therefore go out us with a askew neighborhood , which goes against some researchers perception of world-wide system .
Oort Cloud
The Oort Cloud is the furthest and most grand potential solar system boundary , widen up to around 100,000 AU from the sun , grant toNASA .
" People who define the solar organization as everything that is gravitationally leap to the Sun deal the boundary of the Oort cloud to be the edge of the solar system , " Reisenfeld said .
For some researcher , this is the clear choice for a solar organization boundary because in hypothesis , a erratic organization consists of all objects orb a star .
" I do n’t understand how anyone considers anything other than the Oort Cloud to be the edge of the solar system,“Sean Raymond , an stargazer at the Bordeaux Astrophysics Laboratory in France , state Live Science in an email . " Any other definition seems ludicrous . It is literally the edge of where something can orb the Sun . "
However , other researcher think that because the Oort Cloud is located in interstellar space , it lies beyond the solar system even if it is bond to our home adept .
There is also a large amount of uncertainty about where the Oort Cloud really ends , which some would reason makes it just as unreliable a border as the Kuiper Belt .
Which boundary is best?
Out of the three possible boundary , the heliopause is the one that is most often used by researchers , and byNASA , to define the solar organisation ’s edge . This is because it is the promiscuous to trap down and because the magnetic properties on either side of it are significantly unlike .
" I would fence for the heliopause to be the boundary because it really is a bound , " Reisenfeld enunciate . " Once you ’ve passed it , you jazz it . "
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But that does n’t mean that everything beyond the heliopause should be considered an interstellar object , such as the tremendous space rock’Oumuamua , Reisenfeld total . " The Oort Cloud was to begin with part of the same stuff that the planets were formed from , so it is compose of solar system material , not interstellar material , " he said .
But while some researchers are happy to nibble a side in this contestation , others see no reason why the solar system can not have multiple boundaries .
" I would say that there is no actual disputation , " Brown said . " There are just different ways to define it count on what is important for the question you are prove to answer . "
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