According to our theory of solar system formation, why do all the planets orbit the sun in the same direction and in nearly the same plane? Because of the rules of conservation of energy and conservation of angular momentum, any rotating cloud that is in the process of collapsing will always turn into a spinning disk in the end.
Any hypothesis of the birth of the solar system must be able to explain the following set of facts:
1. Each and every one of the planetary orbits is in a forward orientation (i.e. if seen from above the North pole of the Sun they all revolve in a counter-clockwise direction).
2. The orbital planes of all of the planets, with the exception of Pluto, have an inclination toward one another that is less than six degrees (i.e. all in the same plane).
3. Terrestrial planets have a high density and are made up of rocks; Jovian planets, on the other hand, are made up of gas and are much larger.
The earliest meteorites known to exist.
In its most basic form, the nebular hypothesis proposes that our solar system originated from the collapse of a cloud of gas and dust that existed between the stars.
Compounds containing hydrogen
It is a circle at a certain distance from the Sun, beyond which the temperature was low enough for ices to condense. This distance is known as the ice circle.
The amount of the radioactive material that is still available to you will be 0.25 kilogram.
It originated from the debris that was hurled away from Earth when a massive collision occurred.
According to our current understanding of how the solar system came into being, the solar nebula underwent three significant transformations as its size decreased.
It heated up, the velocity at which it rotated accelerated, and it began to flatten out into a disk.
The gravitational collapse of the supermassive black hole gave rise to the formation of our solar system.
The solar system came into existence some 4.6 billion years ago as a result of gravity pulling together a nebula, which is a low-density cloud of interstellar gas and dust (movie).
At first, the cloud stretched over a distance equivalent to many light years. A very little overdensity in the cloud was responsible for the beginning of the contraction, which in turn drove the overdensity to increase and lead to a more rapid process of runaway or collapse.
Although the majority of the movements of the cloud particles at the beginning were random, there was still a net rotation occurring inside the nebula. Because of the conservation of angular momentum, the rate at which the cloud rotated was steadily picking up speed as the process of collapse continued.
The rotating ball collapsed into a thin disk with a diameter of 200 AU (0.003 light years) (twice the orbit of Pluto), also known as the solar nebula (movie), with the majority of the mass concentrated near the center. This occurred because the gravitational collapse was much more effective along the spin axis.
The gravitational potential energy of the cloud was transformed into the kinetic energy of the individual gas particles as the cloud shrank. This energy was transformed into heat by the process of collisions between the particles (random motions). Near the heart of the solar nebula, where most of the mass that would eventually become the protosun was gathered, the temperature reached its maximum (the cloud of gas that became Sun).
A narrow disk that revolves around the sun is responsible for giving birth to planets, moons, asteroids, and comets. Over the course of the last several years, we have accumulated data that lends credence to this notion.
At some point in time, the temperature in the middle reached 10 million Kelvin. The collisions between the atoms were so strong that nuclear processes occurred. It was at this time that the Sun was formed as a star, and it contains 99.8 percent of the entire mass.
What stopped the collapse from being worse? At the same time as the temperature and density grew toward the center, the pressure also increased, which resulted in a net force that was directed outward. After fifty million years, the Sun finally attained hydrostatic equilibrium, which can also be referred to as a balance between the gravitational force and the internal pressure.
The disk barely made about 0.2 percent of the total mass of the solar nebula and was filled with particles that moved around in circular orbits. The disk’s spin halted any further collapse of the disk, which was the intended outcome.
Uniform composition: seventy-five percent of the mass is comprised of hydrogen, twenty-five percent of the mass is comprised of helium, and the remaining two percent of the total is composed of any additional elements.
Because of the release of gravitational energy, the temperature of the material reached several thousand degrees towards the core; as a result, it turned into vapor. Further out, the material was mostly gaseous because hydrogen and helium continue to exist in their gaseous state even when the temperature is extremely low. Because of how widely spaced out the disk was, the force of gravity was insufficient to draw together enough material to create planets.
Where did the rocky building blocks that went into planet creation originate from? The temperature lowered as the disk radiated away its internal heat in the form of infrared radiation (Wien’s law), and as a result, the molecules that were the densest started to condense into very small solid or liquid droplets. This is referred to as the condensation process.
There is a direct correlation between the temperature and the amount of matter that is transformed into a solid (Why is this the case?). Near the Sun, where the temperature was greater, only the heaviest chemicals were able to condense, creating heavy solid grains. These compounds include aluminum, titanium, iron, and nickel, as well as silicates, which condense at temperatures somewhat lower than the former. At the disk’s periphery, temperatures were enough enough for hydrogen-rich molecules to condense into lighter ices, such as water ice, frozen methane, and frozen ammonia. These ices were formed when the temperature dropped below a critical threshold.
The components of the solar system might be broken down into the following four categories:
Metals: iron, nickel, aluminum. They begin to condense at a temperature of less than 1,600 degrees Celsius and make up just 0.2 percent of the disk.
Minerals composed of silicon that crystallize at temperatures between 500 and 1,300 degrees Celsius make up rocks (0.4 percent of the nebula).
Ices are hydrogen compounds such as methane (CH4), ammonia (NH3), and water (H2O), which condense at temperatures below 150 degrees Celsius and account for 1.4% of the mass of ice.
Hydrogen and helium, two light gases that never condensed in the disk, were there (98 percent of the disk).
The significant temperature variations that existed between the hot core regions and the chilly outer areas of the disk controlled the kind of condensates that were accessible for the creation of planets at each position outward from the center. The inner region of the nebula was poor in ices and gases, but it was abundant in heavy solid grains. Ice, hydrogen, and helium are found in abundance on the edges.
This view is supported by evidence provided by meteorites.
The earliest solid particles were of a size that could only be described as tiny. As the gas from which they condensed, they moved about the Sun in almost circular orbits exactly adjacent to them other until they finally collapsed. The flake-like particles were able to adhere to one another and grow into bigger particles as a result of gentle collisions, which then attracted even more solid particles. Accrual is the term used to describe this process.
Planetesimals are the objects that are generated as a result of accretion; they are also known as little planets. Planetesimals serve as the seeds for the construction of planets. At beginning, there was a dense concentration of planetesimals. After a few million years, they merged together to create bigger objects, producing clusters that were up to a few kilometers broad. This is a very short amount of time when compared to the history of the solar system (movie).
When planetesimals reached these sizes, collisions between them became destructive, which made future expansion more difficult (movie). Only the largest planetesimals were able to survive this process of fragmentation. These planetesimals then proceeded to continue their sluggish growth into protoplanets by accreting other planetesimals of a similar composition.
After the protoplanet had formed, the accumulated heat from the radioactive decay of short-lived elements melted the planet, which made it possible for distinct materials to distinguish (to separate according to their density).
The birth of the planets that are terrestrial:
Rock and metal, which had been baked over billions of years in the cores of enormous stars, coalesced into planetesimals in the solar system’s inner regions, where temperatures were higher.
Because these elements made up only 0.6% of the material in the solar nebula (and because the faster collisions between particles close to the Sun were more destructive on average), the planets were unable to grow very large and were unable to exert a significant amount of pull on hydrogen and helium gas.
Even if terrestrial planets have hydrogen and helium, the closeness of such planets to the sun would cause the gases to get heated and lead them to escape.
Because of this, the terrestrial planets (Mercury, Venus, Earth, and Mars) are compact little worlds that are mostly made up of only 2% of the heavier elements that are found in the solar nebula.
Planets like Jupiter may form when:
Planetesimals developed from a combination of ice flakes, stony flakes, and metal flakes as they were forming in the solar nebula’s outermost regions.
Because there was a greater supply of ices, the planetesimals were able to develop into much bigger sizes, which eventually led to their forming the cores of the four jovian planets (Jupiter, Saturn, Uranus, and Neptune).
Because of their enormous size (at least 15 times the mass of Earth), the cores were able to generate a dense atmosphere by nebularly capturing hydrogen and helium gas from their surrounds and releasing it into the atmosphere.
They evolved into the gigantic gaseous and low-density planets that were abundant in hydrogen and helium and had dense solid cores.
Icy planetesimals were able to exist in the nebula even though they were very far from the sun (beyond Neptune) (movie). However, because of the low density of the disk, the ice and dusty planetesimals could only develop to a size of a few kilometers at most. Because they were unable to accrete the gas in their environment, they stayed in the shape of little, filthy snowballs. They are the members of the family of comets known as Kuiper belt comets, which was a prediction of the theory that explained how the solar system was formed and was verified in the year 1990.
Pluto does not qualify as either a terrestrial or a jovian planet since it is tiny, like planets that are classified as terrestrial, but it is also far from the sun and has a low density, like planets that are classified as jovian. In point of fact, there are astronomers who maintain that Pluto is a member of the comet family (probably the largest member).
The asteroid belt, which can be found between Mars and Jupiter, is composed of thousands of stony planetesimals that range in size from one thousand kilometers to only a few meters. It is believed that they are leftovers from the birth of the solar system that were unable to coalesce into a planet because to the influence of Jupiter’s gravity. When large asteroids collide, they break up into smaller pieces that may sometimes be seen falling to Earth. These rocks, which are known as meteorites, are a rich source of knowledge on the solar nebula in its initial state. The vast majority of these pieces are around the size of grains of sand. They combust in the atmosphere of Earth, causing them to shine like meteors as they pass through (or shooting stars).
The same mechanism that generated the solar nebula — contraction, spinning, flattening, and heating — formed comparable but smaller disks of material surrounding these planets. This process was responsible for the early planets in the Jupiter system capturing vast quantities of gas. Within the Jupiter nebulae, condensation and accretion took place, which resulted in the formation of a tiny solar system around each of the Jupiter planets (Jupiter has well over a dozen moons!).
The “double planet theory” states that the planet and its moon formed separately at the same time from the same rocks and dust.
The moons originated in another location and were later “caught” (the “capture theory”). Take Mars as an example. Other candidates for possible capture include Pluto and Charon, as well as maybe several of Jupiter’s moons and moonlets (movie).
The composition of the Moon may be explained by a massive collision between a big planet and a young Earth (movie).
It is estimated that within 50 million to 100 million years, the Sun, planets, moons, comets, and asteroids all formed.
As soon as nuclear burning started in the Sun, it transformed into a brilliant object and cleared nebula. This happened because the pressure from its light and the solar wind drove material out of the Solar System.
Planets were able to contribute to the cleanup effort by ingesting certain planetesimals while expelling others.
Some of the planetesimals had collisions with the planets, which resulted in the formation of craters and other significant repercussions. It’s possible that a massive impact is what tilted Uranus’ axis in the first place. It seems likely that an object the size of Mars collided with Earth, ejecting debris into space that eventually gathered together to create the moon. The first few hundred million years or more saw the great bulk of the planet’s history’s repercussions.
Other planetesimals were propelled to distant regions of the solar system when they came into contact with planets and their gravitational pull.
Planet formation came to a stop when the Solar System was finally free of junk for the most part. Craters may be found on every solid surface in the world today, thanks to meteorites (movie). On the Moon, you can still make out the craters that were left behind, but here on Earth, erosion and other geological processes are slowly filling them up.
Even now, the frequency of impacts is much lower (65 million years ago, an asteroid or comet impact is thought to have caused the extinction of 90 percent of the species on Earth).
Later in the process of the Solar System’s development, Venus, Earth, and Mars each received their own atmospheres:
The early bombardment delivered some of the ingredients from which the atmospheres and seas of the terrestrial planets evolved. [Citation needed] [Citation needed] These chemicals arrived in the inner planets after their original creation, most likely delivered by collisions of planetesimals created in the fringes of the solar system. (Answer to: What was Jupiter’s role in delivering water to Earth?) (Question: What was Jupiter’s role in bringing water to Earth?)
Another possible contributor to the development of the atmosphere is outgassing, which occurs when gas is expelled from volcanoes.
On Earth, the production of oxygen, which is necessary for the survival of animals, resulted from the breakdown of carbon dioxide by plants.
Rings encircling huge planets, like as Saturn’s, are presumably the consequence of stray planetesimals being ripped apart by the planet’s gravity when they strayed too near to the planet. In other words, Saturn’s rings were created when planetesimals got too close to Saturn (movie).
Because they originated on a flat disk, all of the planets follow almost identical paths around the sun in their orbits. The direction in which the disk was spinning eventually became the direction of rotation for the sun, as well as the direction in which the planets orbited around the sun.
According to David DeVorkin, a senior curator in the space history branch of the Air and Space Museum, the reason for this is because of the process through which the sun evolved. Around 4.5 billion years ago, a huge cloud of dust began to shrink as the force of gravity dragged its various components toward the center of the cloud.
Pierre-Simon Laplace, a French astronomer and mathematician, was the first to propose, in the year 1796, that the Sun and the planets originated in a revolving nebula that eventually cooled down and imploded. This nebula, according to the hypothesis, ultimately condensed into rings, which led to the formation of the planets and a core mass that we know as the sun.
In their orbits around the sun, the planets all travel in the same direction and, for the most part, follow the same plane. Additionally, with the exception of Venus and Uranus, they all revolve in the same general direction. This is not the case with Uranus and Venus. It is thought that collisions that took place late in the process of the planets’ creation are the cause of these discrepancies.