Which of the following is the best description of the formation of a giant planet with a massive core? (at least as described in the lectures!)

The formation of a giant planet with a massive core, as described in the lectures, typically follows these steps:

1. The process begins with the formation of a protoplanetary disk around a young star. This disk is composed of gas and dust.

2. Within this disk, solid particles begin to collide and stick together, forming planetesimals. These are small, solid objects that are believed to exist in protoplanetary disks and in debris disks.

3. Over time, these planetesimals continue to collide and merge, forming a planetary core. This is a slow process that can take several million years.

4. Once the core reaches a certain mass (around 10 Earth masses), it has enough gravitational pull to attract the surrounding gas in the disk. This process is known as gas accretion.

5. The gas accretion process is much faster than the core formation, and can result in a giant planet with a massive core and a thick atmosphere of gas. This is how gas giants like Jupiter and Saturn are believed to have formed.

6. Eventually, the protoplanetary disk is depleted, either because the material has been accreted onto planets, or because it has been blown away by the radiation from the star. The newly formed giant planet with a massive core is now a part of the star system.