Gr.9 Space unit exam study chunk 2

Big Bang Theory

The scientific theory that the universe began about 13.8 billion years ago from an extremely hot, dense point and has been expanding ever since.

Big Crunch Theory

A possible future theory where the expansion of the universe stops and gravity pulls all matter back together into a single dense point.

Gravity

A force of attraction between all objects with mass; stronger with more mass and shorter distance.

Stars

Massive balls of hot gas (mostly hydrogen and helium) that produce energy through nuclear fusion.

Sun

A medium-sized star (yellow dwarf) at the center of our solar system that provides light and heat to Earth.

Nuclear Fusion

A process where hydrogen atoms combine to form helium, releasing huge amounts of energy that power stars.

Solar Panels

Devices that convert sunlight into electrical energy using photovoltaic cells.

Star Formation Process

Nebula → gravity pulls gas together → protostar forms → nuclear fusion begins → main sequence star.

Planets (Order from Sun)

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune — ordered by distance from the Sun.

Astronomy

The scientific study of space objects such as stars, planets, galaxies, and the universe.

Constellations

Groups of stars that form recognizable patterns used for identification and navigation.

Solar System

The Sun and all objects that orbit it, including planets, moons, asteroids, and comets.

Rotation

The spinning of an object on its axis (Earth’s rotation causes day and night).

Orbit

The curved path an object follows around another object due to gravity.

Revolution

One complete orbit of an object around another (Earth’s revolution around the Sun is one year).

Satellite

An object that orbits a planet or larger body; can be natural (moon) or artificial.

Moon

A natural satellite that orbits a planet (Earth’s Moon orbits Earth).

Asteroid

A rocky object that orbits the Sun, mostly found in the asteroid belt between Mars and Jupiter.