Formation of the Moon and Nebulae

These flashcards cover key concepts related to the formation of the Moon, collision theory, and nebulae.

What is the collision theory for the formation of the Moon?

The collision theory, also known as the giant impact hypothesis, suggests that the Moon was formed from debris resulting from a collision between a Mars-sized planet called Theia and the early Earth.

What did early 20th-century scientists believe about the formation of the Moon?

They believed that the Moon formed by splitting away from the Earth shortly after the Earth was formed.

How does the Moon's movement relate to its formation theory?

Calculations show that the Moon is still moving away from Earth at about 4 cm each year, which contradicts the idea that it split from Earth.

What evidence supports the collision theory?

The Moon is less dense than Earth, has a small iron core, and its surface was once molten. Additionally, the composition of Earth and Moon rocks is similar.

What evidence contradicts the collision theory?

The Earth's surface does not appear to have been molten during the Moon's formation, and Venus, which is similar to Earth, has no moon despite many expected collisions.

What are nebulae?

Nebulae are large clouds of dust and gas in space, mainly consisting of hydrogen and helium.

What is a stellar nursery?

A stellar nursery is a region in space where new stars are formed from colliding dust and gas.

How does a new star form in a stellar nursery?

Dust and gas collapse under gravity, increasing pressure and temperature, leading to nuclear reactions that create heat and light.

What are the two most common gases found in nebulae?

Hydrogen and helium.

What distinguishes a nebula from a galaxy?

Nebulae are smaller clouds of dust and gas within galaxies, which are much larger collections containing many stars and nebulae.

Describe the main components of the Solar System.

The Solar System consists of the Sun, eight planets, natural and artificial satellites, and minor planets including dwarf planets.

What is the significance of the term light year?

A light year is a unit of distance that represents how far light travels in one year.