Summary: The terrestrial planets created cshed to the Sun where temperatures were well suited for rock and steel to condense. The jovian planets formed outside what is called the frost line, wright here temperatures were low enough for ice condensation.

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Sections:OverviewTerrestrial world formationJovian planet formationRelated Lessons:A Classroom Solar SystemPlanetary Distances on the PlaygroundThe Planets and also ScaleClay PlanetsModeling Sizes of PlanetsAstro-Chronology

In the previous section, we disputed the formation of a star by means of the collapse of a big cloud of gas. It is worth noticing that the eight planets in our solar device make up 2 various groups; the 4 planets closest to the Sun comprise the rocky terrestrial planets and also the 4 planets farthest from the Sun comprise the gaseous jovian planets. Why execute objects that formed from the exact same cloud of gas have actually different compositions? The answer lies in where these objects formed in relation to the parent star, our Sun.

After the solar nebula collapsed to develop our Sun, a disk of product developed roughly the new star. The temperature across this protoplanetary disk was not uniform. Because different materials conthick at various temperatures, our solar device developed various types of planets. The separating line for the various planets in our solar device is called the frost line. In the simulation listed below,notice where hydrogen and also helium condense in the solar nebula.

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Terrestrial Planet Formation


Diagram of the frost line(click to enlarge)
Hydrogen compounds, such as water and also methane, commonly condense at low temperatures, and also reprimary gaseous inside the frost line wright here temperatures are higher. The heavier rocky and also metallic products are much better suited to conthick at better temperatures. Hence, the inner planets are made practically entirely of rock and steel and also create the group well-known as the terrestrial planets.

How did the terrestrial planets form?

After the heavier facets and minerals condensed right into solid bits of rock, they all orbited the Sun at around the very same rate. As you can imagine, collisions of objects moving at the very same speed are much less destructive than those of objects moving at different speeds. Thus, when rocks orbiting the Sun move close to one an additional, they stick together more often than they destroy each various other. These pieces gradually grow larger in a procedure called accretion. Once they are large sufficient, gravity pressures them into spherical forms.

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Jovian Planet Formation


Materials in the solar nebula(click to enlarge)
Outside the frost line, temperatures are cooler and also hydrogen compounds are able to conthick right into ices. Rock and also steel are still present in the outer solar system, yet both are outnumbered and also outweighed by the hydrogen compounds. Thus, the planetesimals that developed in the outer solar device are composed mainly of hydrogen compounds with traces of rock and also steel. Hydrogen and helium do not conthick in the solar nebula, and also are fairly numerous in the big orbits of objects in the external solar system. As the external planetesimals ongoing to flourish bigger, the toughness of their gravity thrived stronger. Surrounding product, mostly hydrogen and helium, is increasingly attracted to the planetesimals as they thrive in size and also the planetesimals accrete more and also more.

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Solar Nebula

How did the Jovian planets form?

The jovian planetesimals soon came to be the icy, dense cores we view today surrounded by astronomical clouds of accreted gas. Much choose the collapse of the solar nebula, these balls of gas deserve to grow big enough to induce gravitational collapse. Remember from the star formation area that gravitational collapse involves heating up, flattening out and rotating much faster. It is possible that as the jovian protoplanets collapsed, smaller pshort articles in the bordering disk formed right into some of the moons that currently orlittle bit the individual external planets. This renders sense, considering that the external planets all have actually many kind of moons and also rings that orbit in the very same airplane, simply prefer the planets in our solar device orlittle the Sun in the exact same aircraft.