Solar nebula theory + Kepler's law

Gravity

________ pulled together the matter and formed planetesimals and eventually planets.

The Solar Nebular Disk Model theory (SNDM)

The theory is that gravity caused the nebula to collapse and eventually started spinning. The accelerating rotation combined with gravity formed a disk. The center of the disk heats up, creating our sun and the solar system. The planets are then formed by accumulating matter from rings in the disk.

Evidence for the Solar Nebular Disk theory

All the planets orbit in the same direction around the Sun and on the same plane

All the inner planets are dense and rocky while the outer is gaseous and large

Planetesimals

Condensed material from the early stages of formation of the solar system. These small objects collide and merge to form a protoplanet.

Early stages of a planet

Planetesimals
Protoplanets

Galaxy's first planet

JUPITER; Many icy planetesimals merged, attracting more of the surrounding dust and gas. Other gas planets like Saturn would follow but would be smaller due to Jupiter having already collected more of the available material

Kepler’s First Law

The orbits of the planets are not a circle. The planets’ orbits is actually an ellipse and the Sun is located at a focus point, which is off to the side rather than the middle.

Kepler’s Second's Law

The planet moves faster when close to the Sun and slower when away from the Sun.