Astrophysics

Question 1

Define the universe

Answer 1

a large collection of billions of galaxies

Question 2

Define a galaxy

Answer 2

a large collection of billions of stars

Question 3

what is a solar system

Answer 3

a collection of planets orbiting a common star

Question 4

where is our solar system

Answer 4

in the milky way galaxy

Question 5

Why does gravitational field strength vary

Answer 5

• it varies with the mass and size of the body
• it is different on other planets and the moon compared to earth

Question 6

What does gravitational force cause

Answer 6

• causes moons to orbit planets
• causes planets to orbit sun
• causes artificial satellites to orbit earth
• causes comets to orbit sun (highly elliptical)

Question 7

Describe the differences in the orbits of comets, moons and planets

Answer 7

• comets = highly elliptical
• moons = slightly elliptical, near constant orbital speed
• planets = slightly elliptical, near constant orbital speed

Question 8

what is a stars colour related to

Answer 8

• The colour of star = surface temperature
• hotter stars = blue
• cooler stars = red

blue hottest
white ^
yellow l
Orange l
red coolest

Question 9

how can stars be classified

Answer 9

• by their colours
• colour depends on how much light they emit

Question 10

describe evolution of a star of similar mass to the sun

Answer 10

nebula - stars form form from a cloud of dust and gas

protostar - force of gravity pulls dust and gas closer together to form protostar. The density increases. More frequent collisions. Temperature increases.

Main sequence star - once protostar is not enough, nuclear fusion reactions happen in core. The star is in equilibrium and stable

Red giant - eventually hydrogen in core begins to run out. Star begins to fuse with helium, causes outer part of star to expand. As star expands, surface cools and becomes red giant

White dwarf - a small to medium sized star like the sun becomes unstable and ejects it’s outer layers of dust and gas. This leaves a hot dense solid core, a white dwarf

Question 11

Describe evolution of star with a mass larger than sun

Answer 11

nebula - stars form form from a cloud of dust and gas

protostar - force of gravity pulls dust and gas closer together to form protostar. The density increases. More frequent collisions. Temperature increases.

Main sequence star - once protostar is not enough, nuclear fusion reactions happen in core. The star is in equilibrium and stable

red supergiant - eventually hydrogen in core begins to run out. This causes outer part to expand and become a red supergiant

Supernova - once fusion reactions finally stop, the core of star collapses suddenly and causes gigantic explosion called supernova

neutron star - at the centre of this explosion, a dense body called a neutrons star will form

Black hole - neutron star will collapse continuously under force of gravity until it forms a black hole