How do planets form? Our solar system was formed by a process known as protoplanetary disc formation. In the inner parts of a protoplanetary disc rocky planets form while gas giants form further out. Other planet-forming systems may go through different processes but the basic process remains the same. The concentric gaps of a planet-forming disc contain gas that will eventually be cleared by the gravitational attraction of new planets.
Disks of pre-planetary matter
The disks of pre-planetary matter were formed around young stars. During the formation process the disks of pre-planetary matter were hot and dense with the hotter portions near the star. The disks became cooler as they moved further away from the star and eventually cooled to a level where new solids were formed. Mineral solids would tend to form future rocky planets while ice and rocky elements would make up outer giant planets.
In order for planets to form these disks would need to grow through 12 orders of magnitude in space. Initially planets would be microscopic grains of dust but they eventually accrete into larger particles. Planetesimals would be accreted by gentle collisions with other planetesimals forming their own atmospheres. These disks would eventually reach a stable mass which is enough to hold them in orbit around the star.
Once planets formed the magnetic field would become stronger generating more heat within the protoplanetary disk. As the magnetic field grew stronger the disks would become more prone to accretion. This process would also result in faster evolution of the protoplanetary disk. Ultimately this process would lead to the formation of Jupiter Saturn Uranus Neptune and Uranus.
Star formation
The process of star formation starts with enormous clouds of gas and dust that are accreting onto the newborn star. These regions sometimes referred to as stellar nurseries or star-forming regions are relatively unstable until hydrogen fuses with oxygen and forms helium. Protostars are these stars before the fusion takes place. The emergence of a new star is accompanied by an intense burst of light that blows the surrounding gas cloud away. Once the new star is fully accreted on to the planets it becomes relatively stable due to the outflow of energy from nuclear fusion.
During star formation planets condense in a molecular disc around the young stars. These discs are then consumed by accretion onto the young star and high-energy radiation from the Sun. Earth’s formation is a bottom-up process. The planets grow from a disc of dust grains until they form giant planets. Occasionally giant planets may form through a large-scale fragmentation or collapse of the outer disc. Understanding the process of planet formation requires observations across the entire electromagnetic spectrum as well as hydrodynamic chemical and radiative transfer modeling.
Stars in the T-Tauri constellation are usually surrounded by massive circumstellar disks which gradually accrete onto the stellar surface. These disks emit energy at infrared optical and ultraviolet wavelengths. As the star grows in size it begins a nuclear reaction in its central region. This fusion causes the star to become visible. During this period the star is called a T-tauri star and this is the first time that a star can be seen in its visual form.
Gravity
How gravity affects the formation of planets? Gravity is a fundamental force and our solar system has no more or less gravitational pull than any other star. But what exactly is gravitational pull? Gravitational pull occurs because the masses of planets are diluted in comparison to the masses of the sun. The sun’s gravity is enormous and accounts for 99.8% of the mass of the Solar System. Its tentacles stretch far enough to pull the Oort Cloud in.
Unlike other planets which are flat and have no gravity nebulae can have massive gravitational fields. The gravitational pull creates pressure to fuse atoms together. These nebulae eventually grow to become planets. The gravitational fields of large nebulae encourage the formation of familiar shapes. However gravitational pull is not the only factor affecting how planets form.
Gravitational forces can oppose the tendency of objects to form spheres. The strength of these forces depends on the phase of material within the object. For instance the Sun is a giant ball of very hot gas so its mass is not strong enough to resist gravity’s push. Nevertheless other stars are spherical. Until they are bigger than 500 kilometers gravity shapes their shapes.
Squire’s mechanism
If we can reconstruct the early evolution of our solar system’s planets we would have to consider two alternative mechanisms for planet formation. One of these is called settling instability and it occurs when certain grain sizes settle in the planet-forming disk. This mechanism can supercharge the rate at which planets form. It also accounts for the observed eccentricity distribution of massive extrasolar planets. While the mechanism is far from being perfect it seems to be the best candidate to explain the observed non-circular orbits of planets.
One theory posits that the largest bodies in our Solar System are formed by a collision-merger of their embryos. This collision-merger essentially kicks planetary embryos into close orbits with their parent stars. Ultimately this mechanism can lead to the formation of planetary embryos which may be as large as Mars. The other mechanism proposes that giant planets form from chains of embryos and that these processes result in the formation of oligarchic planets.
As the gas cools and contracts onto the core it becomes increasingly massive. If the hydrostatic envelope is unable to keep the core above a critical mass the planet will open a gap in its disk and form a baby gas giant. As the planet grows more massive the gas flow increases. The resulting planets are the terrestrial planets. This mechanism is not as clear-cut as some other theories but it may be an effective way to explain the evolution of Earth.
Hopkins’ mechanism
Researchers have proposed a new mechanism to explain how planets form in our solar system. They believe that the dust in our solar system dragged through a disc of gas when our solar system was young. This process has profound effects on the universe. Dust grains orbiting a gas disk slow down and dust piles up and attracts other dust grains. When these particles get close together they eventually form clumps sheets or filaments.
This process is referred to as a ‘runaway’ process. When large bodies begin to grow faster than small ones their orbital eccentricities increase. This phase lasts for a few years. Alternatively the formation of planetesimals could occur by gravitational collapse of dense regions. Another possibility is the Goldreich-Ward mechanism but it faces substantial challenges. The theory is currently under development.
If this mechanism is correct then the gas disk that surrounds a young star could be a rocky planet. The gas disk could contain boulders pebbles and even mountains. But these chunks could become full-grown planets if they were formed in the presence of a star’s gas disc. This process is a process that can result in planets in our solar system. The new model has many implications for planet formation.
Ramirez-Tannus’ mechanism
According to astronomers massive stars form clusters. These systems contain multiple massive stars that have masses more than eight times the Sun. These massive stars are also binary with small separations between them. Maria Claudia Ramirez-Tannus an astronomer at the Max Planck Institute for Astronomy in Heidelberg led the team that devised this mechanism. Her group of scientists studied the velocity dispersion of massive stars and their binary systems in order to learn more about how they form.
The spectral data collected by the team allow them to determine the age of the clusters. The mass of a cluster is measured from its most massive stars. Using this information they can determine how old the clusters are. The researchers also found a correlation between the velocity dispersion of massive stars in clusters and the age of the cluster. This is because the orbital velocities of these stars increase rapidly with cluster age.
