P16 Space

Question 1

what is at the centre of the solar system?

Answer 1

the sun

Question 2

what is the sun?

Answer 2

a star

Question 3

what are the relatively small, rocky planets?

Answer 3

Mercury
Venus
Earth
Mars

Question 4

what are the larger planets in the solar system?

Answer 4

Jupiter
Saturn
Uranus
Neptune

Question 5

what are moons?

Answer 5

natural satellites which orbit planets

Question 6

what is a galaxy?

Answer 6

a massive group of stars

Question 7

how do stars form?

Answer 7

they form from clouds of dust and gas (a nebula)
in the first stage, gravity causes the nebula to collapse
as the particles move faster, the temperature rises forming a protostar
if the temperature increases enough, it will cause the hydrogen nuclei to undergo nuclear fusion and form helium
this releases a huge amount of energy

Question 8

what are the forces inside a star?

Answer 8

the force of gravity acts inwards and makes the star collapse
the energy from nuclear fusion acts outwards and makes the star expand

Question 9

what is a nebula?

Answer 9

a cloud of dust and gas

Question 10

what is the main sequence of a star?

Answer 10

a stable stage in the life cycle of a star where nuclear fusion occurs
there is a balance between the outwards force of radiation and the inwards force of gravity

Question 11

what happens to stars that are the same size as the sun?

Answer 11

the hydrogen begins to run out so the outwards force due to fusion becomes smaller
the force of gravity causes the star to collapse inwards which increases the temperature
helium nuclei fuse together to make heavier elements and the star expands to form a red giant
the star then stops fusing helium and shrinks to a white dwarf
the star cools down and stops releasing energy and forms a black dwarf

Question 12

what happens to stars much bigger than the sun?

Answer 12

when they run out of hydrogen, they expand to form red super giants
helium nuclei fuse together to form heavier elements
fusion then stops and the star explodes in a supernova

Question 13

which elements are produced in a supernova and why?

Answer 13

elements heavier than iron
as the temperature is high enough

Question 14

what happens to the elements made in a supernova?

Answer 14

they are distributed across the universe when the supernova explodes

Question 15

what can be formed from a supernova?

Answer 15

a neutron star
a black hole

Question 16

what is a neutron star?

Answer 16

neutrons densly packed together

Question 17

what is a black hole?

Answer 17

a great amount of matter packed into a very small area
the gravity is so large that light cannot escape

Question 18

what is a circular orbit?

Answer 18

when a satellite’s orbit follows the path of a circle

Question 19

what is an eliptical orbit?

Answer 19

when planets follow the path of an elipses?

Question 20

what holds a planet in orbit?

Answer 20

the force of gravity between the sun and the planet

Question 21

what are geostationary satelites?

Answer 21

satelites which orbit once around the earth every 24 hours so always point at the same point on the earth

Question 22

why does the force of gravity on a satellite cause a change in velolity but not in speed?

Answer 22

the velocity is speed in a given direction
in a circular orbit, the direction of the satellite is constantly changing so the velocity is constanty changing
the speed is constant

Question 23

what happens if the speed of a satellite orbiting the earth changes?

Answer 23

the radius of the orbit must change
if the speed increases, the radius decreases
this is because the object needs a greater force of gravity to stop it from flying out to space

Question 24

what does a decreased radius of a satellite’s orbit cause?

Answer 24

the gravitational force on the satellite is greater and it stays in a stable orbit

Question 25

what are the properties of light from distant galaxies?

Answer 25

it has a longer wavelength than light from closer galaxies

Question 26

what are the dark lines on an absorbtion spectrum of light from a star and why do they appear?

Answer 26

they are where elements in the star absorb certain wavelengths of light

Question 27

what is red-shift?

Answer 27

the change in wavelength of light from distant galaxies to the red end of the spectrum

Question 28

how does red-shift show that galaxies are moving away?

Answer 28

as they are moving away, the light waves are stretched so their observed wavelengths are increased

Question 29

if a galaxy has a larger red shift, what does it mean?

Answer 29

the galaxy is further away and moving faster

Question 30

what is the evidence for the universe expanding?

Answer 30

the fact that distant galaxies are moving faster than nearer galaxies

Question 31

what is the big bang theory?

Answer 31

that the universe formed from a small region that was hot and dense and expanded into the universe

Question 32

what is the strange thing that scientists observed around 1998?

Answer 32

the rate of expansion of the universe is increasing which cannot be explained

Question 33

what is a suggestion for the reason the universe is expanding faster?

Answer 33

there is matter and energy we cannot detect called dark matter and dark energy

Question 34

what between distant galaxies and earth is expanding?

Answer 34

the space between us

the galaxies aren’t moving away by travelling through space