Astrophysics revision

Question 1

Universe definition

Answer 1

collection of billions of galaxies

Question 2

Galaxy defintion

Answer 2

collection of billions of stars and their solar systems

Question 3

Our solar system

Answer 3

the milky way

Question 4

Thanks to gravitational force:
- moons orbit
- planets orbit
- artificial satellites orbit
- comets orbit

Answer 4

• planets
• the sun
• the earth
• the sun

Question 5

Orbit of comets

Answer 5

• have elliptical orbits
• most kinetic, GPE and speed when closest to sun
• comet tail always points away from sun

Question 6

Orbit of moons

Answer 6

• circular orbit
• tidally locked so same side of moon always faces the planet
• orbit matches with Earth’s rotation

Question 7

Orbit of planets

Answer 7

• circular

Question 8

orbital speed formula

Answer 8

orbital speed:
2 x π x orbital radius
over
Time period

Question 9

How can stars be classified based on colour and whats the order highest to lowest.

Answer 9

Color based on surface temp:
Dark blue, lighter blue, white, light yellow, yellow, orange, red

Question 10

Stages of a star similar/ smaller mass than Sun and brief description of each

Answer 10

• nebula - clouds of gas and dust which contact under gravity
• main sequence - stable and fusing hydrogen to form helium. Gravity vs radiation pressure
• red giant - hydrogen core runs out, pressure contracts core, produces carbon and oxygen, lots of energy produced. red giant explodes to form…
• white dwarf - the hot dense solid core left behind
• black dwarf - white dwarf cools to leave black dwarf

Question 11

Stages of star larger than Sun

Answer 11

• becomes a red supergiant instead, which produces enough energy to form heavier elements (up to iron)
• runs out of fuel, core collapses, supernova explosion where elements heavier than iron form
• core becomes a neutron star, or star becomes a black hole

Question 12

What is absolute magnitude

Answer 12

How bright a star would appear if it were 10 parsecs away. Reverse scale (lower number means brighter)

Question 13

Axis of a hertzsprung-russel diagram

Answer 13

x axis - temp
y axis - absolute magnitude

Question 14

Two most important arguments supporting Big Bang Theory

Answer 14

Cosmic microwave background radiation and red shift

Question 15

Redshift equations (they equal each other)

Answer 15

change in wavelength/wavelength of reference galaxy

velocity of galaxy/speed of light

Question 16

Redshift definition

Answer 16

wavelength of light changing as it moves away from us, so it moves towards the red end of the spectrum

Question 17

How does redshift probve universe expansion

Answer 17

Red shift is changing meaning the universe is moving further away