space🌚

Question 1

what are moons

Answer 1

natural satellites which orbit planets

Question 2

what is the solar system a part of

Answer 2

the milky way galaxy

Question 3

what is a galaxy

Answer 3

a massive group of stars

Question 4

how do stars form

Answer 4

1. stars form from clouds of dust and gas (a nebula)
2. gravity causes the cloud of dust and gas to collapse ( a protostar)
3. as the dust particles move faster, the temperature rises to millions of degrees celsius
4. if the temperature of the protostar gets high enough, then hydrogen nuclei join together to form helium, this is called nuclear fusion
5. nuclear fusion releases a lot of energy
6. There are two forces acting on a star :
   - the force of gravity acts inwards and makes the star collapse
   - the energy from nuclear fusion causes a force to act outwards on the star causing it to expand
7. The star is in equilibrium as these 2 forces are balanced

Question 5

what is the main gas in a nebula

Answer 5

hydrogen

Question 6

what galaxy is our solar system a part of

Answer 6

the milky way

Question 7

what is the main gas in a nebula

Answer 7

hydrogen

Question 8

describe the early lifecycle of stars

Answer 8

1. stars begin life as a cloud of dust and gas which is a nebula
2. gravity causes the cloud of dust and gas to collapse
3. as the particles move faster, the temperature rises to millions of degrees C
   ( this early stager is called a protostar)
4. if temperature gets high enough then hydrogen nuclei join together using nuclear fission to form helium
   (at this point, we have a main sequence star)

Question 9

what happens to stars that are around the same size as our sun

Answer 9

• in a main sequence star, hydrogen fuse together to create helium
• at some stage, the hydrogen in the star begins to run out
• at this point, the outward force due to fusion energy is less than the inward force due to gravity
• this causes the star to collapse inwards
• this collapse causes the star’s temperature to increase
• the helium nuclei fuse together to make heavier elements
• the star expands to form a red giant
• at some point the red giant stops fusing helium, and at this point, the star shrinks and becomes a white dwarf
• because the white dwarf isnt carrying out fusion, it gradually cools down
• eventually, it stops releasing any energy and forms a black dwarf

Question 10

what happens to stars that are bigger than our sun

Answer 10

• once these stars run out of hydrogen, they expand into a red super giant
• helium nuclei fuse together to produce heavier elements
• at some point, red super giant stops carrying out nuclear fusion
• at this stage the star explodes and this is called a supernova and elements from it are distributed throughout the universe
• after a supernova, the remains of a star can form a neutron star or a black hole

Question 11

what elements can nuclear fusion make

Answer 11

any element lighter than iron, cannot be heavier than iron

Question 12

where do elements that are heavier than iron come from

Answer 12

when a star explodes and becomes a supernova, its temperature is high enough to produce elements heavier than iron

Question 13

what is a neutron star

Answer 13

one that consists of neutrons densely packed together

Question 14

what is a black hole

Answer 14

one that has such a large gravity that even light cannot

Question 15

what holds planets in their orbit

Answer 15

the force of gravity

Question 16

what might the force of gravity lead to in circular orbits

Answer 16

a change in velocity, but not a change of speed

Question 17

why does the speed not change for objects in circular orbit, but the velocity does

Answer 17

because velocity is the speed of an object in a given direction, since the direction is constantly changing, the velocity is constantly changing

Question 18

what must happen if the speed of a satellite changes

Answer 18

the radius of the orbit must also change

Question 19

what happens if the speed of a satellite increases and why

Answer 19

the radius decreases, this is because at a higher speed, the satellite needs a greater force of gravity to prevent it flying off into space

• by moving closer to earth, the gravitational force on the satellite is greater and the satellite remains in a stable orbit

Question 20

what happens if a satellite is moving too quickly

Answer 20

the gravitational attraction between the Earth and the satellite is too weak to keep it in orbit. If this is the case, the satellite will move off into space. This occurs at speeds around or above 11,200 metres per second (m/s).

Question 21

what would happen if a satellite is moving too slowly

Answer 21

the gravitational attraction will be too strong, and the satellite will fall towards the Earth. This occurs at speeds below 7600 m/s.

Question 22

what is a stable orbit

Answer 22

one where the satellite is moving at a just right speed, and will travel along the right path without falling down or flying into space

Question 23

what does a change in velocity result in

Answer 23

acceleration

Question 24

when will an object accelerate if its moving in a circle

Answer 24

an object will accelerate if there is a resultant force on it, for objects moving in a circle, this force is called a centripetal force, which acts towards the middle of the circle

Question 25

what provides the centripetal force needed to keep satellites in orbit

Answer 25

gravitational attraction

Question 26

how does gravitational attraction link to distance

Answer 26

the closer the two objects are to each other, the stronger the force of gravity between them.

Question 27

why do objects in small orbits travel faster than objects in larger orbits

Answer 27

If the gravitational force between two objects is greater, a greater acceleration will occur. The greater the acceleration, the greater the change in velocity - this causes the object to move faster.

Question 28

what happens during the main sequence phase of the star

Answer 28

- gravitational attraction tends to collapse the star - radiation pressure from the fusion tends to expand the star -forces caused by gravitational attraction and fusion energy are balanced

Question 29

what fusion reaction takes place in a star

Answer 29

Two hydrogen nuclei fuse to produce a helium nucleus and a neutron.

Question 30

what is red shift

Answer 30

There is an observed increase in the wavelength of light from most distant galaxies. The further away the galaxies, the faster they are moving and the bigger the observed increase in wavelength - they shift to the red end of the spectra

Question 31

why does red shift happen

Answer 31

- because light waves get stretched as they make their way to earth - because of the space between the Earth and the galaxies expanding

Question 32

how can we tell how fast a galaxy is moving away from the earth

Answer 32

The more red-shifted the light from a galaxy is, the faster the galaxy is moving away from Earth

Question 33

what does the red shift provide evidence for

Answer 33

the big bang theory

Question 34

what does the big bang theory suggest

Answer 34

that the universe began from a very small region that was extremely hot and dense, and it expanded into the universe we see today

Question 35

what did the observations of supernovae prove

Answer 35

that the rate of expansion is increasing

Question 36

what is dark mass and dark energy

Answer 36

matter and energy in the universe which we cannot detect

Question 37

how can we tell that the universe is expanding

Answer 37

distance galaxies are moving faster than nearby ones

Question 38

how do some scientists believe the universe began

Answer 38

from a very small region that was extremely hot and dense