Astrophysics

Question 1

what is the universe

Answer 1

the universe is a large collection of billions of galaxies

Question 2

what are galaxies

Answer 2

a galaxy is a large collection of billions of stars

Question 3

what galaxy is our solar system in

Answer 3

the milky way galaxy

Question 4

what are the planets

Answer 4

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune

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Question 5

define weight

Answer 5

The force acting on an object due to gravitational attraction

Question 6

asteroids vs comets

Answer 6

asteroids are lumps of rock and metal which orbit the sun
comet are lumps of ice and dust which orbit the sun

Question 7

universe vs galaxy

Answer 7

A galaxy is a large collection of stars,
whereas the Universe is made up of billions of galaxies.

Question 8

what is the milky way

Answer 8

The Milky Way is a galaxy containing billions of stars, including our Sun.

Question 9

what do weight and GFS vary on

Answer 9

The greater the mass of the planet then the greater its gravitational field strength

A higher gravitational field strength means a larger attractive force towards the centre of that planet or moon

Question 10

state what these object orbit around

planet
moon
comet
asteroid
artificial satalites

Answer 10

planet - sun
moon - planet
comet - sun
asteroid - sun
artificial satalites - earth

Question 11

how can we describe why things orbit the way they do

Answer 11

Smaller bodies orbit around larger bodies

Question 12

what is orbital motion

Answer 12

Orbital motion is a result of the gravitational force of attraction acting between two bodies

Question 13

what does the gravitational force in an orbital motion always do
(and causes what)

Answer 13

always acts towards the centre of the larger body

causes the orbiting body to move in a circular path

Question 14

similarites of planet which orbit the sun

Answer 14

Their orbits are all slightly elliptical (stretched circles) with the Sun at one focus (approximately the centre of the orbit)

They all orbit in the same plane

They all travel in the same direction around the Sun

Question 15

differences of planet which orbit the sun

Answer 15

They orbit at different distances from the Sun (different orbital radius)

They orbit at different speeds

They all take different amounts of time to orbit the Sun

Question 16

what does the distance from the sun have to do with the way the planet orbits it

Answer 16

The further away a planet is from the Sun, the slower it travels and therefore the longer it takes to orbit

Question 17

what is the orbital motion of the moon

Answer 17

Moons orbit planets in a circular path

Some planets have more than one moon

The closer the moon is to the planet:
- the shorter the time it will take to complete each orbit
- the greater the speed of the orbit

Question 18

what is the orbital motion of comets

Answer 18

Their orbits are highly elliptical (very stretched)

• As the comet approaches the sun, its speed increases
• As it moves further away from the sun, its speed decreases

Question 19

what is orbital period

Answer 19

The time taken for an object to complete one orbit

Question 20

how are stars classified

Answer 20

their color because the colour they emit depends on how hot they are

Question 21

relation of temp and color with a star

Answer 21

the HOTTER star will be blue
the COOLER star will be red

Question 22

what happens to stars as they change

Answer 22

When a star becomes a red giant it becomes redder as it expands and cools

When a star becomes a white dwarf it becomes whiter as it contracts and heats up

Question 23

life cycle of a LOW mass star

Answer 23

nebula
gravitational collapse
main sequence star
red giant
planatary nebula
white dwarf

Question 24

life cycle of a HIGH mass star

Answer 24

nebula
gravitational collapse
main sequence star
super red giant
super nove
either:
- neutron star
- black hole

Question 25

what is a nebula

Answer 25

giant interstellar cloud of gas and dust

Question 26

what does a stars brightness depend on

Answer 26

the luminosity the distance of the star from earth

Question 27

what is luminosity

Answer 27

The total amount of light energy emitted by the star Luminosity is a measure of a star's brightness or power output

Question 28

what is apparent magnitude

Answer 28

The perceived brightness of a star as seen from Earth

Question 29

what is absolute magnitude

Answer 29

A measure of how bright stars would appear if they were all placed the same distance away from the Earth

Question 30

what is a Hertzsprung-Russell diagram and how are stars ordered

Answer 30

This is a plot of luminosity on the y-axis and temperature on the x-axis For stars which are brighter than the Sun, luminosity > 1 For stars which are dimmer than the Sun, luminosity < 1

Question 31

state the 4 areas A, B, C, D

Answer 31

A = white dwarf stars B = main sequence stars C = red supergiant stars D = red giant stars

Question 32

describe key areas of a HR diagram

Answer 32

The brightest stars (high luminosity) are found near the top The dimmest stars (low luminosity) are found near the bottom The hottest stars (high temperature) are found towards the left The coolest stars (low temperature) are found towards the right

Question 33

what is the big bang theory

Answer 33

Around 14 billion years ago, the Universe began from a very small region that was extremely hot and dense Then there was a giant explosion, which is known as the Big Bang

Question 34

what are the 2 main peices of evidence for the big bang

Answer 34

Galactic red-shift Cosmic Microwave Background (CMB) radiation

Question 35

what is evidence that the universe is shifting

Answer 35

redshift in the light from distant galaxies

Question 36

What conclusions have astronomers made from these red shift observations

Answer 36

All galaxies are moving away from the Earth. Galaxies are moving away from each other. This expansion is expected after an explosion.

Question 37

How does matter behave after an explosion?

Answer 37

Matter starts densely packed and moves outward in all directions. Lighter matter moves faster and travels further. Heavier matter moves slower and stays closer to the source.

Question 38

How is the distance of a galaxy related to its speed?

Answer 38

The further a galaxy is, the faster it moves. The closer a galaxy is, the slower it moves.

Question 39

What is Cosmic Microwave Background (CMB) radiation

Answer 39

It is a type of electromagnetic radiation that is a remnant from the early stages of the Universe.

Question 40

Why is CMB classified as microwave radiation

Answer 40

It has a wavelength of around 1 mm, placing it in the microwave region of the electromagnetic spectrum.

Question 41

What does the Big Bang theory say about the early Universe

Answer 41

the whole Universe was a very small, extremely hot and dense region

Question 42

How has the wavelength of the CMB radiation changed over time

Answer 42

As the Universe expanded, the wavelength increased, shifting it into the microwave region.

Question 43

what does CMB's pattern suggest

Answer 43

The CMB radiation is very uniform and has the exact profile expected to be emitted from a hot body that has cooled down over a very long time

Question 44

what can we use the doppler shift for

Answer 44

The doppler shift equation can be used to calculate the velocity of a galaxy if its wavelength can be measured and compared to a reference wavelength

Question 45

What happens to the observed frequency and wavelength when a wave source moves relative to an observer

Answer 45

If the wave source moves toward the observer: Frequency increases ( blue shift for light). Wavelength decreases (waves are compressed). If the wave source moves away from the observer: Frequency decreases (red shift for light). Wavelength increases (waves are stretched).

Question 46

what is a redshift

Answer 46

Red-shift is the increase in wavelength of light from objects that are moving away from you

Question 47

How does the red-shift of galaxies provide evidence for the expansion of the universe?

Answer 47

Red-shift shows that galaxies are moving away from Earth. The greater the distance, the faster the galaxy moves away (Hubble’s Law). This supports the Big Bang Theory, which suggests the universe began from a single point and has been expanding ever since.