The Universe - Unit 2

Question 1

Major features in the universe

Answer 1

Galaxies, stars, solar systems, nebulae

Question 2

outline what a nebula is

Answer 2

a large cloud made of interstellar gas and dust that mark the beginning of a new star or are the remnants of supernovas.

Question 2

outline what a star is

Answer 2

stars are giant balls of hot gas and plasma held together by gravity. stars are composed primarily of hydrogen, helium and small amounts of other elements.

Question 2

ouline what a galaxy is

Answer 2

giant collections of stars, gas and dust, held together by the attractive force of gravity. The majority of galaxies feature a central bulge and a flattened disc. The different types of galaxy include ellipitical, spiral and irregular.

Question 3

outline what a solar system is

Answer 3

a solar system consists of a star and one or more planets which orbit the star

Question 4

1 AU

Answer 4

150 million km

Question 5

proportions

Answer 5

-> galaxies are typically 100,000 light years in diameter
-> 100 billion stars in each galaxy
-> stars are generally a million kilometers in diameter or so
-> distance between earth and sun is around 150 million km

Question 5

light year

Answer 5

the distance that light travels (going at 300,000km/s) in a year

Question 6

star birth

Answer 6

Stars form from vast clouds of gas and dust called nebulae. A small disturbance can cause the cloud to collapse, until the star becomes hot enough for nuclear fusion to begin. The newborn star is called a protostar

Question 7

small star life

Answer 7

nebula -> main sequence star -> red giant -> planetary nebula -> white dwarf -> white dwarf cooling -> black dwarf

Question 8

large star life

Answer 8

nebula -> main sequence star -> supergiant -> supernova -> neutron star or black hole

Question 9

telescopes

Answer 9

Instruments that collect and focus light and other forms of electromagnetic radiation using lenses, mirrors and reflecting dishes.

Question 10

Optical telescopes

Answer 10

Can only see the very narrow band of visible light
Two types: Reflectors + refractors
Reflectors use a series of curved and angled mirrors to focus light whereas refractors use a series of lenses to magnify the images.
Advantage - Available to general public
Disadvantage - Chromatic abberation, lens distortion

Question 10

Radio telescopes

Answer 10

Gather radiation and focus it to a point where it can be observed
Advantage - Unaffected by clouds, can be used in day and night
Disadvantage - More complicated to obtain good quality images that show all the details of celestial objects

Question 10

Different types of telescopes

Answer 10

Optical
radio
Infrared and x-ray telescopes
Space telescopes

Question 11

Infrared and x-ray telescopes

Answer 11

Tend to be space-based
Infrared light emitted from very hot space objects can be seen using infrared and x-ray telescopes
Advantage - Able to see objects within dusty clouds
Disadvantage - Ground based infrared telescopes need to be kept at very high altitudes which is a cumbersome process

Question 12

Space telescopes

Answer 12

Get around the Earth’s atmosphere so that we can get a clearer view of planets stars and galaxies.
Advantage - Are not obstructed by the Earth’s atmosphere
Disadvantage - Very expensive to build and to maintain

Question 13

Discoveries made with telescopes

Answer 13

Galileo used his optical telescope to discover that Venus had phases, proving that it orbits around the Sun and not the Earth.
Radio telescopes have discovered several powerful radio galaxies and qasars.
Space telescopes such as the NEOWISE probe have been used to detect comets, asteroids and other space objects.
Radio telescopes found CMB radiation
Hubble used his telescope to find that galaxies were moving away from us (red shift)

Question 13

Describe the Big Bang Theory

Answer 13

The Big Bang theory states that the universe expanded from a very small dense point about 14 billion years ago and has been continuing to do so.

Question 14

Different models of describing the origin of the universe

Answer 14

-> Earth-centred universe
-> Sun-centred universe
-> Steady state theory
-> Big bang theory

Question 14

Identify and outline the evidence for the expanding universe (big bang) theory

Answer 14

Red shift - wavelengths emitted from objects had shifted towards the red end of the electromagnetic spectum, proving that they were moving away from earth
Cosmic Microwave Background Radiation - The CMB is incredibly uniform in all directions, with only tiny fluctuations in temperature suggesting that the universe was once in a very hot, dense, and uniform state, as expected from the Big Bang. The fact that we see the same temperature everywhere, even in the farthest reaches of the universe, indicates that the early universe was once in a nearly uniform, thermal equilibrium state before it began expanding and cooling.
Abundance of elements - The relative amounts of hydrogen and helium are consistent with the amounts that are predicted to have been producing after the big bang.

Question 15

Errors in theories

Answer 15

Geocentric universe -> The planets orbit the Sun and the Earth is not at the centre of the universe
Heliocentric universe -> The universe has more in it than just stars and a few planets, the sun is not at the centre of our universe. Copernicus assumed there were circular orbits, but this lead to many inaccurate calculations.
Steady state theory -> Observations of distant galaxies show that they are very different from nearby galaxies — more irregular, with less structure and more star formation. This suggests that the universe has evolved over time. The Steady State theory couldn’t explain this evolving nature of galaxies because it assumed that the universe was in a steady, unchanging state.

Question 16

Reliability, accuracy, validity

Answer 16

How consistent the results are, how close the results are to other findings and known information, whether the controlled variables were kept the same and the experiment was fair

Question 17

dependent variable and independent variable

Answer 17

y axis, x axis : right column, left colum