Question

and dust in space called nebulae. star formation begins with gravitational collapse, during which an area of gas and dust within a nebula collapses in on itself due to its increasing mass and gravity. as matter collapses in on itself due to gravity, it becomes very dense. this causes the pressure and temperature to drastically increase, forming a protostar. as the protostar gathers more matter via gravity, its internal pressure and temperature can become extreme enough for hydrogen atoms in its core to fuse together to form helium atoms. thus, a new star is born. after a new star forms, it is still surrounded by a large cloud of gas and dust. this cloud rotates around the new star and flattens into a protoplanetary disk. over time, the new star absorbs most of the disks nearby matter, while the more distant matter condenses into clumps with greater masses and densities than those of surrounding objects. gravity can pull these clumps of dust, ice, and rocks together to form comets, asteroids, or the building blocks of planets and moons. these objects gravitational influences increase as they gain more matter and become more massive. eventually, planets and moons can form, and the protoplanetary disk can become a new planetary system. this is the process by which the solar system formed. how are star and planet formation similar? stars and planets both form as a result of a large decrease in temperature and pressure. stars and planets both form due to increasing gravitational forces pulling in more matter. stars and planets both form when hydrogen atoms fuse to form helium atoms. stars and planets both form from protoplanetary disks.

Explanation:

1. The first option is incorrect: star formation involves a drastic increase in pressure and temperature, not a decrease.
2. The second option is correct: Stars form when gravity pulls nebula gas/dust into a dense protostar, gathering more matter via gravity. Planets form when gravity pulls clumps of dust/ice/rocks in a protoplanetary disk together, with their gravitational pull growing as they collect more matter. Both rely on increasing gravitational forces to accumulate mass.
3. The third option is incorrect: Only stars undergo hydrogen-helium fusion in their cores; planets do not.
4. The fourth option is incorrect: Stars form first from nebulae, and protoplanetary disks form around new stars, from which planets develop. Stars do not form from protoplanetary disks.

Answer:

Stars and planets both form due to increasing gravitational forces pulling in more matter.