Grade 8 Life Sciences: The Solar System, Gravity & Life on Earth

Vocabulary flashcards covering the components, celestial bodies, gravitational mechanics, planetary details, and life-supporting conditions of the Solar System based on Grade 8 Life Sciences notes.

Celestial body

Any natural object in space that exists outside of Earth's atmosphere.

Gravity

The natural force of attraction that pulls any two objects with mass toward each other.

Orbit

The curved path of an object as it moves around another object.

The solar system

A disc-shaped collection of celestial bodies held together by the gravity of the Sun.

Asteroid belt

A region in our solar system located between the orbits of Mars and Jupiter that contains millions of rocky bodies.

Year

The total time it takes for a planet to finish one full orbit around its host star, lasting $365.25$ days on Earth.

Sol

The Latin name for the Sun, from which terms relating to the Sun (such as 'Solar') are derived.

The Sun

A medium-size star that produces its own energy, is the central and largest body of the solar system containing $99\%$ of all its mass, and is approximately $150\,000\,000\text{ km}$ away from Earth.

Nuclear fusion

Nuclear reactions taking place within the Sun that release large amounts of heat and energy to power the Sun at temperatures reaching $15\text{ million }^\circ\text{C}$.

Photosphere

The outer surface of the Sun that provides Earth with the perfect temperatures for life to persist.

Inner planets (Rocky planets)

The four planets located inside the asteroid belt (Mercury, Venus, Earth, and Mars) that are made of solid mass.

Outer planets (Gas giants)

The four planets located outside the asteroid belt (Jupiter, Saturn, Uranus, and Neptune) that are made of gas and are larger than rocky planets.

Mercury

A solid planet that is closest to the Sun ($58\text{ million km}$ away), contains tiny amounts of hydrogen and helium on its surface, and takes $88$ Earth days to complete one orbit.

Venus

The second planet from the Sun ($108\text{ million km}$ away) with carbon dioxide and sulphuric acid clouds, which spins the opposite way to other planets and takes $255$ Earth days to orbit the Sun.

Earth

The third planet from the Sun ($150\text{ million km}$ away), having mainly nitrogen and oxygen in its atmosphere, which is the only planet able to sustain life and takes $365.25$ Earth days to orbit the Sun.

Mars

The fourth planet from the Sun ($249\text{ million km}$ away), having carbon dioxide, nitrogen, and argon in its atmosphere, known as the 'red planet' due to red iron oxide (rust) dust on its surface, and taking $687$ Earth days to orbit the Sun.

Jupiter

The fifth planet from the Sun ($780\text{ million km}$ away) and the largest planet in the solar system; a giant gas planet with rings, an atmosphere of hydrogen and helium, and an orbital period of $12$ Earth years.

Saturn

The sixth planet from the Sun ($1430\text{ million km}$ away); a gas giant with hydrogen and helium in its atmosphere, known for its colourful rings made of ice-coated rock fragments, taking $30$ Earth years to orbit the Sun.

Uranus

The seventh planet from the Sun ($2280\text{ million km}$ away); a gas giant with rings, an atmosphere containing hydrogen and helium, and an orbital period of $84$ Earth years.

Neptune

The eighth planet from the Sun ($4500\text{ million km}$ away) with hydrogen and helium in its atmosphere, named after the Roman god of the sea due to its blue colour, taking $164$ Earth years to orbit the Sun.

Dwarf planet

A celestial body that orbits the Sun and has enough mass to form a round shape, but has not cleared other objects out of its orbital path.

Pluto

A celestial body previously classified as a planet that was reclassified as a dwarf planet in 2006 because it did not fit the new category of what a planet is.

Moon

A natural celestial body that orbits a planet, dwarf planet, or other minor body in space, which does not produce its own light but reflects light from the Sun.

Europa

One of Jupiter's $115$ moons.

Luna

The Latin name for Earth's permanent moon.

Asteroids

Large, lumpy chunks of rock and metal that orbit around the Sun, tumbling and spinning as they travel; the term originates from a Greek word meaning 'star shaped'.

Comets

Large chunks of ice and rock (known as 'dirty snowballs') that orbit the Sun and move through the outer edges of the solar system, forming a glowing head and a tail of gases as their ice melts near the Sun.

Halley's comet

A famous comet that orbits the Sun every $76$ years and can be seen from Earth as it passes.

Short period comets

Comets that originate from the Kuiper belt and take less than $200$ years to orbit the Sun.

Kuiper belt

A region of the solar system that lies beyond the planets and contains millions of icy objects, including dwarf planets.

Long period comets

Comets that originate from the Oort cloud and take thousands of years to complete one orbit around the Sun.

Oort cloud

A collection of billions of comets located about one light year from the Sun beyond the Kuiper belt, whose outer limit defines the outer boundary of the solar system.

Astronomical unit (AU)

A unit of distance used in the solar system defined as the distance from Earth to the Sun, where $1\text{ AU} = 150\,000\,000\text{ km}$.

Elliptical orbit

The oval-shaped pathway along which planets move and revolve around the Sun.

Orbital motion mechanism

The movement of planets revolving around the Sun caused by the combination of an inward gravitational pull from the Sun and the planet's sideways velocity.

Altitude

The height above sea level; as altitude increases, temperatures become colder.

Ocean currents

The direction of flow of ocean water; currents moving from the equator carry warmth to other regions, while water moving from the poles cools areas it passes.

Photosynthesis

The process needed by plants to make food (sugars) using radiant energy provided by the Sun.

Cellular respiration

The life process carried out by living things where sugars are broken down using oxygen to release energy for life processes.

Atmospheric Nitrogen

A gas comprising $78\%$ of the air we breathe, which is used by plants to produce proteins.

Atmospheric Oxygen

A gas comprising $21\%$ of the air we breathe, produced by plants and utilized by living things for cellular respiration.

Atmospheric Carbon Dioxide

A gas comprising $0.03\%$ of the air we breathe, produced by animals and used by plants to make food (sugars).