SP7- Astronomy

Question 1

What is the geocentric model

Answer 1

The idea that the sun and all planets orbit the Earth - there is a sphere of fixed stars

It’s a theory by Ptolemy

Question 2

What’s the heliocentric model

Answer 2

Nicholas Copernicus thought the sun was at the centre of our solar system

Question 3

What is good about the invention of the telescope to support heliocentric model

Answer 3

We can see new objects - Galilean moons of jupiter , by plotting there movements jt showed not everything orbited earth is Galileo supported Copernicus

Question 4

What’s our current model of the universe like

Answer 4

8 planets, 5 dwarf planets, thousands of comets and millions of asteroids

These all move in elliptical orbsit around the sun - many of which have natural satellites

Question 5

Tell me about photography and astronomy

Answer 5

More detailed observations

Computers for analysis

Question 6

Why are some telescopes placed in space

Answer 6

In order to detect radiation otherwise absorbed by the atomsphere

Question 7

What is weight

Answer 7

The force of gravity acting on you

Question 8

What does weight depend on

Answer 8

Gravitational field strength (g)

Question 9

What’s the gravitational field strength of earth

Answer 9

9.8 N/kg

1kg of mass is 9.81 N

Question 10

What does the gravitational field strength on the surface of a body surface of a body such as a planet or a moon depend on

Answer 10

Mass of the body and the distance from its centre to its surface (radius)

Greater the mass and smaller it’d radius, greater its surface of gravity

Question 11

What shape are most bodies orbits in the solar system

Answer 11

Elliptical

Comets are highly elliptical whereas planets can be almost circular

Question 12

What does the type of orbit an artificial satellite has depend on

Answer 12

What it is used for

Question 13

For satellites: what are highly elliptical orbits used for

Answer 13

Communication in parts of the earth near the poles

Question 14

Tell me about a satellite in polar orbit

Answer 14

It will eventually pass over all parts of the world - orbit goes through poles

Question 15

Tell me about satellites in geostationary circular orbits

Answer 15

They remain over one point on Seth and are used for broadcasting

Question 16

Tell me about satellites with low earth orbits

Answer 16

Need the least fuel to launch and travel very very fast

Question 17

Tell me about a satellites speed and velocity

Answer 17

It’s Speed is constant as it travels but it’s direction is changing constantly - an orbiting body has a constantly changing Velocity

Question 18

Why does gravity change the satellites direction but not speed

Answer 18

A moving object would continue to go in a straight line unless there’s a force acting to make it change speed or direction - the gravitational force between the earth and the satellite is at right angles to the direction of movement so the force changes its direction

Question 19

Why does a satellite in low orbit have to move much faster to stay in its orbit than a high orbit

Answer 19

If it slows it will fall towards the earth, it will gain speed as it falls and then be fast enough to stay in a new lower orbit where it count encounter the top of the atmosphere and contact with air will make it slow down and fall to earth

Question 20

What is a nebula

Answer 20

A cloud of dust and gases (mainly hydrogen)

Question 21

How does a nebula form into a protostar

Answer 21

Materials can be pulled together by their own gravity, as the cloud (nebula) contracts it becomes denser, the hydrogen becomes hotter as it spirals inwards and may start to glow, as more mass is attracted - gravity gets stronger and heats material more - this is a protostar

Question 22

When does a protostar become a main sequence star

Answer 22

Eventually temperature and pressures in centre of a protostar evoke high enough to force hydrogen nuclei to fuse together and form helium - fusion reactions like this release a lot of energy as electromagnetic radiation, outward pressure from hot gases balance compression from gravity, it’s now in main sequence stage of life awwww

Question 23

Why does a main sequence star not collapse?! (What is balanced)

Answer 23

Pressures from hot gases and compression due to gravity

Question 24

When does a red giant form after a main sequence

Answer 24

When they have fused most of their hydrogen into helium, the core core is not hot enough to withstand gravity and it collapses - outer layers expand to form a red giant

Question 25

How does a red giant survive

Answer 25

Other fusion happens - convincing helium Nuclei to form heavier elements

Question 26

When does a white dwarf form

Answer 26

When a red giant throws off a shell of gas, the rest of the star is pulled together by gravity and collapses to form a white dwarf - no fusion happens in a white dwarf

Question 27

When does a black dwarf form

Answer 27

After a white dwarf, there’s no fusion so gradually it cools over about 1 billion years

Question 28

Tell me just the names of the stages of the life cycle of a star the size of our sun

Answer 28

Cloud of gas -> protostar-> main sequence star -> red giant -> shell of gas -> white dwarf -> black dwarf

Question 29

What’s different in the stages of a massive main sequence star

Answer 29

When a main sequence has considerable more mass than the sun, they fuse helium into to hydrogen faster and are brighter and hotter, they become red supergiants and after rapidly collapse and explode into a supernova. The outer layers are cast off and expand outwards

Question 30

What happens after a supernova ?

Answer 30

If what is left is 4x or more the mass of sun, gravity pulls remains together to form a black hole

If the remains are not so massive - gravity pulls them together to form a very dense star called a neutron star

Question 31

The gravitational pull of a black hole is so strong not even….

Answer 31

Light can escape!!!

Question 32

What is the principle of the Doppler effect

Answer 32

The pitch of a sound depends on the frequency of the wave - sound waves behind a moving vehicle /source become stretched to make the wavelength longer to lower frequency, opposite happens when source of sound is in front

This opposite happenw if the source of the sound is moving relative to the observer, if you are travelling in a car with the same speed the sound would not change idiot #basic

Question 33

How are light waves redshifted

Answer 33

Similar to the Doppler effect - lines are moved toward the red end of the spectrum, the star is moving a way from us - the more the lines are shifted, the faster the star is moving

The redshift is a measure of how far along the spectrum the lines have moved

Question 34

What happens when pattern of lines move towards the blue spectrum

Answer 34

The star must be moving towards us as the wavelength and frequency of the light waves become shorter and so the pattern of lines move towards the blue end of the spectrum

Question 35

How did Edwin Hubble use redshift to show the universe is expanding

Answer 35

Investigated pattern of line shifted for 50 galaxies in comparison to the sun, discovered almost all were red shifted and moving away - further away the galaxy, the greater the redshift and so faster it’s moving away from us - interpret this relationship to mean that the universe is expanding

Question 36

What is the Big Bang theories

Answer 36

First suggested in the 1920s - says that the whole universe and all the matter in it started out as a tiny point of concentrated energy 13.5 billion years ago, it expanded from this point and is still expanding

As the universe expanded, gravity caused matter to clump together to form stars

Question 37

What’s the steady state theory

Answer 37

Suggested in 1948, theory says the universe has always existed and is expanding, new matter is continuously created within the universe as it expands

Question 38

What is cosmic microwave background radiation

Answer 38

The big band states that huge amounts of radiation were released at the beginning of the universe, becuase the universe is expanding, wavelength has increased so it’s only detectable as microwave radiation

Question 39

What universe creation story is most believed

Answer 39

Both the steady state and Big Bang theory say the universe is expanding - redshift support both

But CMB shows evidence for Big Bang only, steady state can’t explain it so since there’s more supporting evidence for Big Bang is more widely accepted