•There is also a point, called___________ , where the object is closest to the sun.

The inward force that causes an object to move in a circular path

•As the nebula contracted during the formation of the solar system, it began to rotate with increasing speed and flattened out into a disk, called ________________, where our sun formed

all objects in the universe attract each other through gravitational force

The protostellar disk became the _________ in which the planets formed

•Collisions between these bodies formed larger bodies, called ___________, from which planets formed.

The collisions of rocky planetesimals in the inner disk led to the formation of rocky, metallic planets

•As the sun was forming, dust grains collided and stuck together to form _______, which increased in size to form meter-sized bodies.

the outer planets have rocky or metallic cores and deep atmospheres of gas and ice

the square of the orbital period is proportional to the cube of the planet’s distance from the sun

Kepler then proposed that each of the planets has an elliptical orbit, with the sun at one focus of the ellipse

•Kepler found that a planet moves slower at aphelion, sweeping out a narrow sector on the ellipse, conversely, a planet moves faster at perihelion, sweeping out a thick sector on the ellipse.

Study the 4 scientists and how they each contributed to the science community. :)