G 9 : revision unit 1 / 2 / 3

theory assumed that the origin of the solar system was from the explosion of the expanded part of the Sun of forming a gaseous line of a great length from the Sun due to a huge star approached to it.

• Nebular

• Big Bang

• Crossing star.

• Modern

The solar system consists of _______ planets.

• 9

• 8

• 7

• 6

Within minutes of Big Bang, helium gas was formed by a percentage of

• 25%

• 50%

• 75%

• 100

The Sun takes about _____ million years to complete one rotation around the center of the galaxy.

• 300

• 320

• 200

• 220

The nebular theory about the evolution of the solar system was found by _______.

• Newton.

• Laplace.

• Moulton

• none

The continuous expansion of the cosmic space because _______

• the movement of galaxies to each other

• the movement of galaxies closer

• the movement of galaxies apart

• none

4. Eight planets including the Earth rotate around the galaxy.

• true

• false

Each group of stars is gathered in the solar system.

• true

• false

The solar system is located at the edge of the Milky Way galaxy.

• true

• false

After 5000 million years from the Big Bang, the Milky Way galaxy took its ___________ form

• sphere

• circular path

• disk

• none