Protoplanetary disk

Definition

A protoplanetary disk is a rotating disk of dense gas and dust surrounding a newly formed star, where planets and other celestial bodies begin to form. These disks are crucial in the early stages of solar system formation, providing the material necessary for the accretion of solid bodies that eventually become planets, moons, and other objects in a planetary system.

5 Must Know Facts For Your Next Test

1. Protoplanetary disks typically form from the leftover material of the molecular cloud that collapsed to create a new star.
2. The temperature and pressure within a protoplanetary disk can influence the composition of the forming planets, affecting whether they become rocky or gaseous.
3. Angular momentum plays a critical role in the dynamics of protoplanetary disks, influencing how material is distributed and how quickly it rotates around the central star.
4. Observations of protoplanetary disks have been made using radio telescopes, allowing scientists to study their structure and composition in detail.
5. Many exoplanets have been discovered in systems with observed protoplanetary disks, supporting theories about how planetary systems form around stars similar to our Sun.

Review Questions

• How does the process of accretion in a protoplanetary disk lead to the formation of planets?
  • Accretion in a protoplanetary disk occurs when tiny particles of dust and ice begin to stick together due to gravitational attraction and electrostatic forces. As these particles grow larger, they can collide with other particles, leading to further growth into larger bodies called planetesimals. Over time, these planetesimals continue to collide and merge, ultimately forming the planets we observe today in solar systems. This process is essential for creating solid bodies from the gas and dust present in the disk.
• Discuss the role of temperature and pressure variations in shaping the outcomes of planet formation within protoplanetary disks.
  • Temperature and pressure variations within a protoplanetary disk significantly impact what types of planets can form. In regions closer to the star, higher temperatures prevent volatile compounds from condensing, resulting in rocky planets like Earth. In contrast, further out where it's cooler, gases like hydrogen and helium can condense into icy bodies leading to gas giants like Jupiter. These environmental conditions thus dictate not just the composition but also the architecture of the resulting planetary system.
• Evaluate how observations of protoplanetary disks have changed our understanding of planetary system formation across different stellar environments.
  • Observations of protoplanetary disks using advanced telescopes have revealed diverse structures and compositions that suggest different pathways for planetary system formation. For example, some disks display clear gaps or rings that indicate interactions with forming planets, while others are more uniform. These findings suggest that planet formation is influenced by various factors including initial mass of the disk, distance from the star, and even magnetic fields. Such insights challenge previous models that assumed a one-size-fits-all approach to planetary system formation, highlighting the complexity and variety across different stellar environments.

Related terms

Accretion: The process by which particles clump together to form larger bodies, such as planets, from dust and gas in a protoplanetary disk.

Nebula: A giant cloud of gas and dust in space, often the site of star formation, which can evolve into a protoplanetary disk around a new star.

Planetesimal: Small solid objects that form from the dust and ice in a protoplanetary disk and can collide and merge to create larger bodies like planets.