Ch16 Space

Question 1

Formation of a protostar

Answer 1

Particles in a nebula(cloud of dust and gas) are pulled together by the force of gravity
Clouds merge together, becoming more concentrated to form a protostar

Question 2

What happens to a protostar to make a main sequence star

Answer 2

As the protostaar becomes more dense, the particles speed up and collide more so the temperature increases
When the temperature becomes high enough, hydrogen nuclei undergo nuclear fusion to form helium nuclei
Energy is released, keeping the core hot

Question 3

What is a main sequence star?

Answer 3

Long stable period where the outward force of nuclear fusion(expansion) is in equilibrium with the force of gravity pulling everything inwards(contraction)
The bigger the star, the shorter the main sequence
It radiates energy because hydrogen fusion in the core

Question 4

How does a red (super) giant form?

Answer 4

The main sequence star runs out of hydrogen nuclei
The core collapses and the outer layer swells
The surface cools and turns red
The fusion of helium(+ other elements) occur to form heavier elements(up to iron) in the core

Question 5

How does a white dwarf form?

Answer 5

When there are no more light elements in the core of a small-medium sized red giant, fusion stops and radiation stops
The star becomes unstable, collapses and ejects outer layer of dust and gas
It heats up and turns form red to white
It is now a hot, dense, solid core called a white dwarf

Question 6

How does a black dwarf from?

Answer 6

White dwarf cools down and emits less energy, fading out

Question 7

How does a supernova form?

Answer 7

Red super giants undergo more fusion, glow bright and contract and expand several times,
It forms elements as heavy as iron in various nuclear reactions
Eventually it will cataclysmically explode into a supernova

Question 8

How do new planets and stars form?

Answer 8

When a red super giant explodes into a supernova, the heavy elements made are ejected into the universe to form new planets and stars

Question 9

How are neutron stars formed?

Answer 9

Exploding supernova throws outer layer of dust and gas into space
The core of the star compresses, leaving a very dense core made up of only neutrons

Question 10

How are black holes formed?

Answer 10

If star is big enough, it becomes a black hole instead of a neutron star
It is a very super dense point with a gravitational field strength so strong nothing can escape from it

Question 11

Big Crunch

Answer 11

If density of universe is more than particular amount, it will stop expanding and reverse

Question 12

Big Yawn

Answer 12

If density of universe is less than a particular amount, it will expand forever
Stars and everything else will die out

Question 13

Dark matter

Answer 13

Missing mass that can’t be seen

Galaxies would be spinning much faster if stars were the only matter

Question 14

Evidence for big bang

Answer 14

1) Big Bang created high energy gamma radiation. As the universe expanded, the wavelengths stretched out to create low energy cosmic background radiation in every direction in space
Detected in 1965

2) Red-shift- provides evidence the universe is expanding

Question 15

Red Shift

Answer 15

Use a prism to split light into a spectrum(blue to red)
Wavelengths of waves increase if the body is moving away
Spectrum of light is shifted towards the red part of the spectrum

Question 16

Blue Shift

Answer 16

Use a prism to split light into a spectrum(blue to red)
Wavelengths of waves decrease if the body is moving towards you
Spectrum of light is shifted towards the blue part of the spectrum

Question 17

Solar mass

Answer 17

1M0 = 1.99 x 10^30kg

The mass of our sun

Question 18

Average temperature in space

Answer 18

4 Kelvin

-269.15 degrees Celsius

Question 19

Age of Universe

Answer 19

13 billion years old(+ or - 1 billion years)

Question 20

Shift rule

Answer 20

The faster a star or galaxy is moving relative to you, the bigger the shift is

Question 21

Steady State Theory

Answer 21

Galaxies are being pushed apart because of matter entering the universe through ‘white holes’

Question 22

Further the smaller body is from the bigger body

Answer 22

1. the less particular speed needed because the force of gravity is weaker
2. The longer the orbiting body takes to orbit around once because the circumference is bigger

Question 23

Order of the planet from the sun

Answer 23

Mercury - my
Venus - very
Earth - easy
Mars - method
Jupiter - just
Saturn- speeds
Uranus - up
Neptune - nothing

Question 24

Who discovered the expanding universe and when

Answer 24

Edwin Hubble in 1929

Question 25

Dark energy

Answer 25

Unknown source of energy scientists believe is causing acceleration of distant galaxies away from each other (Big Ride)
Observed in supernova since 1998

Question 26

Big Bang Theory

Answer 26

Universe expanding after exploding suddenly from a very small, hot and dense region
Space, time and matter were created
Since 1998, observations of supernovae suggest distant galaxies are receding even faster

Question 27

Speed of planet in orbit

Answer 27

doesn’t change

Question 28

Forces of orbit

Answer 28

Force on orbiting body is the force of gravitational attraction between it and the larger body

Question 29

Orbit around the sun

Answer 29

force of gravity on the planet from the sun acts towards the centre of the sun(centripetal force)
it is the resultant force on the planet because no other forces act on it

Question 30

acceleration of a planet in orbit

Answer 30

it experiences acceleration towards the centre of the circle because of resultant force acting towards it

Question 31

velocity of a planet in orbit

Answer 31

direction of a planet’s orbit is changed by the centripetal force
direction of velocity in a circular orbit is at a right angle to the direction of force of gravity(directed towards the centre)