Summary: The terrestrial planets developed close to the Sun wbelow temperatures were well suited for rock and also steel to conthick. The jovian planets developed outside what is dubbed the frost line, wbelow temperatures were low sufficient for ice condensation.

You are watching: Why are terrestrial planets denser than jovian planets?


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

In the previous area, we discussed the formation of a star using the collapse of a large cloud of gas. It is worth noticing that the eight planets in our solar device make up two various groups; the 4 planets closest to the Sun make up the rocky terrestrial planets and also the 4 planets farthest from the Sun comprise the gaseous jovian planets. Why perform objects that developed from the exact same cloud of gas have actually various compositions? The answer lies in wbelow these objects developed in relation to the parent star, our Sun.

After the solar nebula collapsed to develop our Sun, a disk of product formed about the brand-new star. The temperature throughout this protoplanetary disk was not unidevelop. Because different products conthick at different temperatures, our solar device developed various types of planets. The splitting line for the various planets in our solar device is called the frost line. In the simulation listed below,notification wright here hydrogen and helium conthick in the solar nebula.


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Terrestrial Planet Formation


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Diagram of the frost line(click to enlarge)
Hydrogen compounds, such as water and also methane, generally condense at low temperatures, and also reprimary gaseous inside the frost line wright here temperatures are higher. The heavier rocky and metallic materials are much better suited to condense at better temperatures. Thus, the inner planets are made almost totally of rock and metal and form the team well-known as the terrestrial planets.

How did the terrestrial planets form?

After the heavier aspects and also minerals condensed right into solid bits of rock, they all orbited the Sun at around the same rate. As you have the right to imagine, collisions of objects relocating at the very same rate are less terrible than those of objects relocating at different speeds. Thus, when rocks orbiting the Sun relocate cshed to one one more, they stick together more frequently than they ruin each various other. These pieces gradually flourish bigger in a process called accretion. Once they are large enough, gravity pressures them right into spherical forms.


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Jovian Planet Formation


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Materials in the solar nebula(click to enlarge)
Outside the frost line, temperatures are cooler and also hydrogen compounds are able to condense into ices. Rock and metal are still current in the outer solar system, yet both are outnumbered and also outweighed by the hydrogen compounds. Therefore, the planetesimals that formed in the outer solar device are composed mostly of hydrogen compounds via traces of rock and steel. Hydrogen and helium perform not conthick in the solar nebula, and are fairly abundant in the big orbits of objects in the external solar system. As the outer planetesimals continued to thrive larger, the stamina of their gravity grew more powerful. Surrounding product, generally hydrogen and helium, is significantly attracted to the planetesimals as they thrive in dimension and the planetesimals accrete more and even more.

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Solar Nebula

How did the Jovian planets form?

The jovian planetesimals soon became the icy, thick cores we see today surrounded by huge clouds of accreted gas. Much like the collapse of the solar nebula, these balls of gas have the right to prosper big enough to induce gravitational collapse. Remember from the star development area that gravitational collapse entails heating up, flattening out and rotating faster. It is feasible that as the jovian protoplanets collapsed, smaller pwrite-ups in the neighboring disk developed right into some of the moons that now orlittle the individual outer planets. This makes sense, given that the outer planets all have many type of moons and also rings that orlittle bit in the same airplane, just like the planets in our solar system orbit the Sun in the very same plane.