Astronomers think planets formed from interstellar dust and gases that clumped together in a process called _____.
stellar evolution
nebular aggregation
planetary accretion
nuclear fusion
nebular aggregation
planetary accretion
The correct answer is "planetary accretion". This is the process by which small particles such as dust and gas in a protoplanetary disk gradually come together to form larger objects, eventually leading to the formation of planets.
To arrive at this answer, astronomers have studied the formation of planets through observations and simulations. They have found that planets form within protoplanetary disks, which are rotating disks of gas and dust that surround young stars. Over time, the particles in these disks collide and stick together through a process called accretion. This gradual accumulation of material leads to the formation of larger bodies, known as planetesimals. These planetesimals then continue to collide and merge, eventually building up the cores of planets. This process of planetary accretion is considered to be the primary mechanism behind the formation of planets in our solar system and other planetary systems.