Astrophysics GCSE

Universe

Large collection of stars and galaxies

Galaxy

Large collection of billions of stars

Solar System

Collection of. planets orbiting a star

Gravitational Field Strength

Force per unit of mass on a body (N/kg)

Formula for weight

weight = mass x gravity

What shape is moon orbit

Elliptical

What orbits the sun?

Planets and comets

Comet orbit shape

highly elliptical

What is an artificial satellite

A man made object orbiting a planet

Formula for orbital speed

2 x pi x orbital radius / time period

Why do comets get a greater speed closer to a star?

Ice inside melts and mass decreases

What does a star begin as

Nebula

What is a nebula

a cloud of gas and dust

What happens to particles in a nebula

Particles clump together due to gravity until temp and pressure are right for nuclear fusion

What happens during nuclear fusion in a nebula

Hydrogen nuclei fuse together to form helium nuclei which release a large amount of outward pressure which balances with inward pressure due to gravity. It's now a main sequence star

What happens once the hydrogen is used up?

No longer enough outward pressure from nuclear fusion and it collapses under its own gravitational attraction, becoming unstable

What happens once it's unstable and it is a similar size to the sun?

Becomes red giant, white dwarf, black dwarf

What happens once it's unstable and it is larger than the sun?

becomes red super giant, supernova then neutron star or black hole

What does brightness depend on?

Where it's measured

What is absolute magnitude?

Apparent magnitude at 10 pc distance

What is apparent magnitude?

how bright a star appears from earth

What is a HR diagram

A plot or graph of luminosity versus temperature (or color index) for stars.

What is the Big Bang theory

The theory that the Universe began with a huge explosion.

What is red shift

An observed increase in the wavelength of light from distant galaxies.

What is CMBR

Cosmic microwave background radiation. Leftover radiation from the big bang that has been red shifted to microwave length.

What is the doppler effect

A change in sound frequency caused by motion of the sound source, motion of the listener, or both.

change in wavelength / reference wavelength

velocity of galaxy / speed of light