There are three ways that planetary rings ( the rings around planets ) have been proposed to have formed: from material of the protoplanetary disk that was within the Roche limit of the planet and thus could not coalesce to form moons ; from the debris of a moon that was disrupted by a large impact ; or from the debris of a moon that was disrupted by tidal stresses when it passed within the planet's Roche limit.

Thus the dust is more likely created by a debris disk around Vega, rather than from a protoplanetary disk as was earlier thought.

Simulations have shown that the presence of a binary companion can actually improve the rate of planet formation within stable orbital zones by " stirring up " the protoplanetary disk, increasing the accretion rate of the protoplanets within.

The natural satellites orbiting relatively close to the planet on prograde, uninclined circular orbits ( regular satellites ) are generally believed to have been formed out of the same collapsing region of the protoplanetary disk that created its primary.

Fomalhaut's dusty disk is believed to be protoplanetary, and emits considerable infrared radiation.

This remnant cloud is the protostar's protoplanetary disk, where planets may form.

The disk concentrates at the core to form a star, which may be surrounded by a protoplanetary disk.

This implies that an unknown process depleted oxygen-16 from the Sun's disk of protoplanetary material prior to the coalescence of dust grains that formed the Earth.

Alternatively, planetesimals can form in a very dense layer of dust grains that undergoes a collective gravitational instability in the mid-plane of a protoplanetary disk.

Star formation is a complex process, which always produces a gaseous protoplanetary disk around the young star.

The protoplanetary disk is an accretion disk which continues to feed the central star.

As a result they are several times more massive than in the inner part of the protoplanetary disk.

Various simulations have demonstrated that the merger of embryos in the inner part of the protoplanetary disk leads to the formation of a few Earth-sized bodies.

Current theories are unable to explain how their cores can form fast enough to accumulate significant amounts of gas from the quickly disappearing protoplanetary disk.

A protoplanetary disk forming in the Orion Nebula

Under certain circumstances the disk, which can now be called protoplanetary, may give birth to a planetary system.

Because planetesimals are so numerous, and spread throughout the protoplanetary disk, some survive the formation of a planetary system.

According to the Solar Nebular Disk Model, rocky planets form in the inner part of the protoplanetary disk, within the snow line, where the temperature is high enough to prevent condensation of water ice and other substances into grains.

The first one is the disk instability model, where giant planets form in the massive protoplanetary disks as a result of its gravitational fragmentation ( see above ).

In this model giant planet formation is divided into two stages: a ) accretion of a core of approximately 10 Earth masses and b ) accretion of gas from the protoplanetary disk.

This happens when a gap opens in the protoplanetary disk.

It stops when the protoplanetary disk disappears or when the end of the disk is attained.

A protoplanetary nebula ( PPN ) is an astronomical object which is at the short-lived episode during a star's rapid stellar evolution between the late asymptotic giant branch ( LAGB ) phase and the following planetary nebula ( PN ) phase.

The Oort cloud is thought to be a remnant of the original protoplanetary disc that formed around the Sun approximately 4. 6 billion years ago.

It is thought that the active magnetic fields and strong solar wind of Alfvén waves of T Tauri stars are one means by which angular momentum gets transferred from the star to the protoplanetary disc.

It has provided ground-breaking studies of the Galactic center, and is also used to study protoplanetary disks, and high-mass star-forming regions.

The ultimate dissipation of protoplanetary disks is triggered by a number of different mechanisms.

A protoplanetary disk is a rotating circumstellar disk of dense gas surrounding a young newly formed star, a T Tauri star, or Herbig Ae / Be star.

The oldest protoplanetary disk ever discovered is 25 million years old.

Cha 110913-773444 is an example of a rogue system with a protoplanetary disk speculated to contain as many as 4 satellites.

IRAS 19024 + 0044 is a protoplanetary nebula in Aquila.

The Calabash Nebula, also known as the Rotten Egg Nebula or by its technical name OH 231. 84 + 4. 22, is a protoplanetary nebula ( PPN ) 1. 4 light years ( 13 Pm ) long and located some 5, 000 light years ( 47 Em ) from Earth in the constellation Puppis.

Gomez's Hamburger is believed to be a young star surrounded by a protoplanetary disk.

However, recent results suggest that this object is a young star surrounded by a protoplanetary disk whose distance is only around 900 light-years away.

The name protoplanetary nebula is an unfortunate choice due to the possibility of confusion with the same term being sometimes employed when discussing the unrelated concept of protoplanetary disks.

A carbon planet, also referred to as a diamond planet or carbide planet, is a theoretical type of planet proposed by Marc Kuchner that could form if protoplanetary discs are carbon-rich and oxygen-poor.

Accretion discs are an ubiquitous phenomenon in astrophysics ; active galactic nuclei, protoplanetary discs, and gamma ray bursts all involve accretion discs.

A planetary system and various minor objects such as asteroids, comets and debris, can form in a hierarchical process of accretion from the protoplanetary disks that surrounds newly created stars.

Use of the term accretion disk for the protoplanetary disk leads to confusion over the planetary accretion process.

In this context, accretion refers to the process of cooled, solidified grains of dust and ice orbiting the protostar in the protoplanetary disk, colliding and sticking together and gradually growing, up to and including the high-energy collisions between sizable planetesimals.

The protoplanetary disk may be considered an accretion disc because gaseous material may be falling from the inner edge of the disk onto the surface of the star, but this process should not be confused with the accretion process thought to build up the planets themselves.

According to scientific consensus, the earth formed in orbit around the sun about 4. 5 billion years ago by accretion from a protoplanetary disk, and remained near its original orbit until the present.

In the nebular theory, accretion refers to the collision and sticking of cooled microscopic dust and ice particles electrostatically, in protoplanetary discs and gas giant protoplanet systems, eventually leading to planetesimals which gravitationally accrete more small particles and other planetesimals.

Use of the term accretion disc for the protoplanetary disc thus leads to confusion over the planetary accretion process, although in many cases it may well be that both accretion processes are happening simultaneously.

Some definitions of the term planet require a planet to have formed in the same way as the planets in our Solar System did, by secondary accretion in a protoplanetary disk.