The scenario you're describing refers to a protoplanetary disk, which is a rotating disk of dense gas and dust surrounding a newly formed star. This environment is crucial for the formation of planets. Here's a brief overview of the key aspects involved:
Formation Process:
-
Star Formation: The process begins with the collapse of a molecular cloud, where regions of high density lead to the formation of a protostar at the center. As the protostar accumulates mass, it heats up.
-
Formation of the Disk: The conservation of angular momentum causes the surrounding material to flatten into a rotating disk. This protoplanetary disk is mainly composed of hydrogen and helium gas, along with various ices, silicates, and organic compounds.
-
Planet Formation: Within this disk, particles of dust and ice start to collide and stick together, forming larger bodies known as planetesimals. Through processes like gravitational attraction and collisions, these planetesimals can grow into protoplanets. Eventually, these protoplanets can coalesce to form fully-fledged planets.
Characteristics of the Disk:
-
Composition: The disk contains a mix of various materials, including gas (primarily hydrogen and helium), ice (water, methane), and dust (silicate minerals, organic molecules).
-
Temperature Gradient: The temperature of the disk varies with distance from the star. It is hotter closer to the star and cooler further away. This gradient affects the types of planets that can form; for example, rocky planets tend to form closer to the star, while gas giants may form farther out where ice can condense.
-
Lifetimes: Protoplanetary disks can last from a few million to tens of millions of years, after which they dissipate due to various processes like the accretion of material onto the star, the formation of planets, and interactions with stellar winds.
Importance for Planetary Systems:
Studying protoplanetary disks helps astronomers understand the conditions under which planetary systems form, including our own Solar System. Observations of these disks in various stages can provide insights into the diversity of planetary systems in our galaxy.
In summary, the disk of gas and dust around a newly formed star plays a fundamental role in the birth of planets, shaping their composition, size, and orbits, leading to the wide variety of planetary systems we observe in the universe today.