2.4 Space physics

What is included in the solar system?

The Sun eight planets dwarf planets moons asteroids and comets

How many stars are in our solar system?

One the Sun

What does heliocentric mean?

The Sun is at the centre of the solar system

Name two dwarf planets

Pluto Ceres

What galaxy is our solar system in?

The Milky Way

Name the planets in order from the Sun

Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune

What are the inner planets made of?

Rock

What are the outer planets made of?

Gas

Do planets orbit on the same plane?

Yes

Do all planets rotate?

Yes but at different speeds

Why do some planets rotate differently?

Past collisions changed their axis

Why do larger planets have rings?

Strong gravity attracts debris

What was the geocentric model?

Earth at the centre with everything orbiting it

What shape were orbits in the geocentric model?

Perfect circles

What replaced the geocentric model?

The heliocentric model

What is the heliocentric model?

Sun at the centre

What evidence supported heliocentric theory?

Retrograde motion of Mars

What is retrograde motion?

Mars appears to move backwards in the sky

Why does retrograde motion happen?

Earth overtakes Mars in orbit

What did Galileo observe?

Moons orbiting Jupiter

What did Kepler discover about orbits?

They are elliptical not circular

What force keeps planets in orbit?

Gravity

Why does a planet’s direction constantly change?

Gravitational force acts towards the Sun

Does a planet’s speed change in orbit?

No only direction changes

What does changing velocity mean?

The object is accelerating

What happens if a planet moves closer to the Sun?

Gravitational force increases

What happens to speed when closer to the Sun?

It increases

Why does orbital speed increase closer to the Sun?

Greater gravitational attraction

What is the first stage of a star’s life?

A cloud of gas and dust

What causes a star to form?

Gravitational attraction pulling particles together

What happens as particles get closer?

Temperature and pressure increase

What process starts in a star?

Nuclear fusion

What elements fuse in stars?

Hydrogen into helium

What does fusion release?

Energy

What balances gravity in a stable star?

Energy from fusion

How long can a star remain stable?

Billions of years

What happens when a star runs out of fuel?

It collapses

What happens to a massive star after collapse?

It forms a supernova

What remains after a massive star?

Neutron star or black hole

What happens to a normal-sized star?

It forms a planetary nebula

What remains after a normal-sized star?

White dwarf

What is red shift?

Light stretched to longer wavelengths

What does red shift show?

Galaxies are moving away

What does red shift provide evidence for?

An expanding universe

What happens to wavelength in red shift?

It increases

What happens to frequency in red shift?

It decreases

What is the Big Bang theory?

The universe began from a single point and expanded

What are two key pieces of evidence for the Big Bang?

Red shift and CMB

What is CMB?

Cosmic Microwave Background radiation

What does CMB show?

The universe was once hot and has cooled

Why is CMB important?

It is found everywhere in the universe

What is still not fully understood about the universe?

Dark matter and dark energy