SP7 Astronomy

Question 1

What is the gravitational field strength on earth?

Answer 1

9.81 N/kg

Question 2

what does gravitational field strength of a planet depend on?

Answer 2

mass of body + distance from centre to surface (radius)

Question 3

what is an elliptical orbit? what is an example of a body that has this orbit?

Answer 3

squished oval shaped orbits - comets are elliptical

Question 4

what are artificial satalites used for?

Answer 4

communication and to observe earth + space

Question 5

What is true about the speed and direction ofcircular orbiting bodies?

Answer 5

the speed is constant but the direction is always changing - a principle of centripetal force

Question 6

How does gravitational force differ from a satalite in low orbit to high orbit? why?

Answer 6

low has greater gravitional force than high - must be moving at a faster speed to stay in orbit

Question 7

What happens when a satalite in low orbit slows down?

Answer 7

fall towards earth - can either gain enough speed to stay in a new, lower orbit, or it will go low enough to make contact with the atmosphere and air will slow it down till it eventually falls to earth

Question 8

How is a star formed?

Answer 8

a nebula (cloud of dust + hydrogen) is formed by materials being pulled together by their own gravity. The cloud then becomes denser and the hydrogen hotter. More mass is attracted and the gravitaional pull of the cloud gets stronger + heats the materials even more. This new formation is called a protostar

Question 9

What fusion reaction takes place in the centre of the protostar? what is released as a result?

Answer 9

hydrogen nuclei fuse to form helium - lots of energy is released like electromagnetic radiation

Question 10

How does a protostar come into its main sequence after a fusion reaction?

Answer 10

the outward pressure of hot gases balances the compression due to gravity

Question 11

what is the life cycle of stars like our sun?

Answer 11

nebula
protostar
main sequence
red giant
white dwarf
(black dwarf once cooled)

Question 12

how long do stars like our sun remain stable for and what causes them to become unstable?

Answer 12

10 billion years - fused all hydrogen + helium together

Question 13

what happens to turn a main sequence star into a red giant?

Answer 13

no more hydrogen to fuse - core is not hot enough to withstand gravity and collapses - outer layers expand

Question 14

what happens to a red giant to form a white dwarf?

Answer 14

a futher pull of gravity and collapse to form white dwarf

Question 15

what is the life cycle of massive starts

Answer 15

nebula
protostar
massive main sequence
red supergiant
supernova
neutron star or blackhole

Question 16

what are massive stars?

Answer 16

stars with considerably more mass than the sun and are hotter and brighter

Question 17

what turns a massive main star sequence into a red super giant?

Answer 17

faster fusing of hydroegn and helium

Question 18

how is a supernova formed?

Answer 18

the end of the red supergiant life cycle - star rapidly collapses and explodes

Question 19

how does a supernova form a black hole?

Answer 19

gravity pulls the remains of the star together if there is enough mass

Question 20

how does a supernova form a neutron star?

Answer 20

if there is not enough mass, gravity pulls the star together to form a small dense star

Question 21

what is the doppler effect?

Answer 21

when an emergancy vehicle moves away from you, the pitch of its siren gets lower

Question 22

What is the scienec behind the doppler effect?

Answer 22

the pitch of sound depends on the frequency of the wave. sound waves behind a moving source become stretched making the wavelength longer which lowers the frequency so we hear a lower pitch. The opposite happens infront of a source

Question 23

what is a red-shift?

Answer 23

when visable ligt of the star moves towards the red end of the spectrum

Question 24

what can we infer from a red-shifted star?

Answer 24

the star is moving away from us

Question 25

How can we tell how fast the star is moving relative to us?

Answer 25

the further the dark lines are shifted to the red end

Question 26

what is the red-shift a measure of?

Answer 26

how far along the spectrum the lines have moved

Question 27

what happens if a star is moving towards us

in terms of wave length and frequency?

Answer 27

wavelength of light becomes shorter and frequency increases so pattern of lines move to blue-end of spectrum

Question 28

How did we come to the conclusion that the earth is exapnding?

Answer 28

Edwin Hubble found that the further away a galaxy is, the greater its red shift and hence the faster it is moving away from us

Question 29

What is the premesis of the Big Bang Theory?

Answer 29

The whole universe and all the matter in it started out as a tiny point of concentrated energy and the universe expanded from this point - as universe expanded, gravity caused matter to clump together to form stars

Question 30

What is the Steady State theory?

Answer 30

states the universe has always existed and is expanding - new matter is created within the universe as it expands

Question 31

What does the Big Bang theory state in terms of raditation?

Answer 31

huge amounts of radiation were released at the begining of the universe - due to expansion, the wavelength of this radiation has increased and is now only detectable as microwave radiation.

Question 32

what is the radiation called that the big bang theory predicted?

Answer 32

cosmic microwave background radiation - or CMB radiation

Question 33

What theory does CMB radiation provide support for?

Answer 33

big bang