Topic 8 - Astrophysics Flashcards
What is the universe made up of?
Billions of galaxies
What is a galaxy made up of?
Billions of stars
What galaxy is our solar system in?
Our solar system is in the Milky Way galaxy
Why does gravitational strength vary between Earth, other planets, the moon, etc…
Gravitational field strength is directly related to an object’s mass, so different planets and space objects have different gravitational field strengths because they have different masses.
What 4 things orbit due to gravitational force?
- Causes moons to orbit planets
- Causes the planets to orbit the sun
- Causes artificial satellites to orbit Earth
- Causes comets to orbit the sun
What is the gravitational force on Earth?
9.81 N/kg (Unless specified otherwise by a question).
How do comets, moons and planets orbit?
Comets orbit in an elliptical shape, but moons and planets orbit in a roughly circular shape.
The equation is v = (2 x π x r) / t, but what are the units and rearrangements?
v = (2 x π x r) / t
t = (2 x π x r) / v
r = (t x v) / 2π
v = orbital speed (m/s)
r = orbital radius (m)
t = time period (s)
How can stars be classified according to their colour?
Stars’ colour relates to their surface temperature, which can be classified into one of the classes:
Blue = More than 33,000 Kelvin surface temp. Class O
White or Blue-White = 10,000-33,000 Kelvin surface temp. Class B
White = 7,500-10,000 Kelvin surface temp. Class A
Yellowish White = 6,000-7,500 Kelvin surface temp. Class F
Yellow = 5,200-6,000 Kelvin surface temp. Class G
Orange = 3,700-5,200 Kelvin surface temp. Class K
Red = 2,000-3,700 Kelvin surface temp. Class M
What is the evolution of a star of similar mass to our sun?
Nebula –> Protostar –> Main Sequence Star –> Red Giant –> Planetary nebular –> White Dwarf
What is the evolution of a star with a much larger mass than the sun?
Nebula –> Protostar –> Main Sequence Star –> Red Supergiant –> Supernova –> Black hole OR Neutron Star, based on what its mass is (higher = neutron star, lower = black hole)
How can the brightness of a star be represented compared to other stars?
Using Absolute magnitude. Absolute magnitude is the luminosity of a star from a standard distance of 10 parsecs (32.6 light-years). For most stars, absolute magnitude is between +15 and -10, with a more negative value being brighter than a more positive one (e.g. -5 is brighter than 20, but -10 is brighter than -5)
How would you draw a Hertzsprung-Russell diagram?
Absolute magnitude is on the y-axis, and colour is on the x-axis.
How do scientists believe the universe formed?
Scientists believe that about 14 billion years ago, all matter in the Universe was in one extremely tiny and dense place. It then exploded and has been expanding ever since.
What is the main evidence for the Big Bang theory? How do these support the Big Bang theory?
Red Shift (Doppler effect) - It shows that the universe is expanding, because galaxies are moving away from each other, and the further away a galaxy is, the faster it is moving away.
Cosmic Microwave Background Radiation (CMBR) - CMBR is the faint glow of radiation left over from the Big Bang. It provides evidence that the universe began from a hot, dense state. It appears to come from every direction and at the same temperature. This supports the idea that the universe started as a hot, dense point and expanded over time, as predicted by the Big Bang Theory.
How will frequency and wavelength change if a wave source is moving relative to an observer?
The wavelength will increase, and therefore the frequency will decrease.
What is the equation relating to change in wavelength, reference wavelength, velocity of a galaxy and speed of light?
How does the red shift of light received from galaxies at different distances away from Earth change?
The further away a galaxy is the greater its red shift and hence the faster it is moving away from us.
Why does the red shift of galaxies provide evidence for the expansion of the universe?
More distant galaxies have greater red-shift and therefore are receding faster because the space between all galaxies is stretching as the universe expands.
