Question

read the passage about star and planet formation.
most stars form within large clouds of gas 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 disk’s 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.
put the steps of the solar system’s formation in the order in which they must have occurred, first.
a large cloud of gas and dust left over from the sun’s formation rotated and flattened.
earth and other planets formed as clumps of dust, ice, and rock gained mass and pulled in even more matter due to increased gravity.
the newly formed protostar gathered matter due to gravity, which increased its internal pressure and temperature.
hydrogen atoms in the protostar’s core fused together to form helium atoms, transforming the protostar into a star, the sun.
gravitational collapse occurred in a dense area of gas and dust within the solar nebula.
matter within the protoplanetary disk condensed into clumps.

Explanation:

To solve this, we analyze the passage and match each step to the formation process:

1. Gravitational collapse starts

The process begins with "Gravitational collapse occurred in a dense area of gas and dust within the solar nebula." (This is the initial collapse of the nebula.)

1. Protostar forms and gains matter

Next, "The newly formed protostar gathered matter due to gravity, which increased its internal pressure and temperature." (After collapse, a protostar forms and accumulates matter.)

1. Protostar becomes a star (fusion)

Then, "Hydrogen atoms in the protostar’s core fused together to form helium atoms, transforming the protostar into a star, the Sun." (Fusion starts, creating the Sun.)

1. Protoplanetary disk forms

After the Sun forms, "A large cloud of gas and dust left over from the Sun’s formation rotated and flattened." (The remaining material forms a rotating disk.)

1. Matter in disk condenses into clumps

Next, "Matter within the protoplanetary disk condensed into clumps." (Disk material clumps together.)

1. Planets form from clumps

Finally, "Earth and other planets formed as clumps of dust, ice, and rock gained mass and pulled in even more matter due to increased gravity." (Clumps grow into planets.)

Order (from first to last):

1. Gravitational collapse occurred in a dense area of gas and dust within the solar nebula.
2. The newly formed protostar gathered matter due to gravity, which increased its internal pressure and temperature.
3. Hydrogen atoms in the protostar’s core fused together to form helium atoms, transforming the protostar into a star, the Sun.
4. A large cloud of gas and dust left over from the Sun’s formation rotated and flattened.
5. Matter within the protoplanetary disk condensed into clumps.
6. Earth and other planets formed as clumps of dust, ice, and rock gained mass and pulled in even more matter due to increased gravity.

Answer:

To solve this, we analyze the passage and match each step to the formation process:

1. Gravitational collapse starts

The process begins with "Gravitational collapse occurred in a dense area of gas and dust within the solar nebula." (This is the initial collapse of the nebula.)

1. Protostar forms and gains matter

Next, "The newly formed protostar gathered matter due to gravity, which increased its internal pressure and temperature." (After collapse, a protostar forms and accumulates matter.)

1. Protostar becomes a star (fusion)

Then, "Hydrogen atoms in the protostar’s core fused together to form helium atoms, transforming the protostar into a star, the Sun." (Fusion starts, creating the Sun.)

1. Protoplanetary disk forms

After the Sun forms, "A large cloud of gas and dust left over from the Sun’s formation rotated and flattened." (The remaining material forms a rotating disk.)

1. Matter in disk condenses into clumps

Next, "Matter within the protoplanetary disk condensed into clumps." (Disk material clumps together.)

1. Planets form from clumps

Finally, "Earth and other planets formed as clumps of dust, ice, and rock gained mass and pulled in even more matter due to increased gravity." (Clumps grow into planets.)

Order (from first to last):

1. Gravitational collapse occurred in a dense area of gas and dust within the solar nebula.
2. The newly formed protostar gathered matter due to gravity, which increased its internal pressure and temperature.
3. Hydrogen atoms in the protostar’s core fused together to form helium atoms, transforming the protostar into a star, the Sun.
4. A large cloud of gas and dust left over from the Sun’s formation rotated and flattened.
5. Matter within the protoplanetary disk condensed into clumps.
6. Earth and other planets formed as clumps of dust, ice, and rock gained mass and pulled in even more matter due to increased gravity.