astrophisc

Question 1

Hubble’s law

Answer 1

recession speed of galaxies is proportional to their distance from earth

Question 2

constellation

Answer 2

• a group of stars that form a pattern in the sky
• but they are not necessarily close to each other

Question 3

stellar cluster

Answer 3

a group of stars (gas and dust) that are held together by gravity

Question 4

apparent brightness

Answer 4

the power per square metre received by an observer on earth

is the amount of ENERGY received per second per unit area by an observer”

Question 5

two different ways in which atomic spectra can be used to deduce physical data for stars

Answer 5

• absorption spectra give information on the element that make up the star
• the peak of wavelength gives information on the temperature of the star
  doppler shift gives information on the stars motion relative to earth

Question 6

parallax angle measured

Answer 6

• relative position of the star to distant background stars is received at two times 6 months apart
• half of the angular shift = parallax angle

Question 7

parallax angle less than 100 pc

Answer 7

beyond this distance the parallax angle is too small to be measured accurately/is less than the uncertainty of the measurement

Question 8

property determine wether a star ends its life as a white dwarf or as a neutron star

Answer 8

mass of the star’s remnant core

Question 9

Chandrasekhar limit - difference between a white dwarf and neutron star

Answer 9

• defines the maximum mass of a white dwarf
• up to this limit electron degeneracy pressure prevents further gravitational collapse
• above this, gravity overcomes this forming a neutron star

Question 10

pulsar

Answer 10

rotating neutron star

Question 11

red super giant star

Answer 11

red in colour
large luminosity
low temperature
large mass
large surface area

Question 12

many regions of the universe that do not contain any stars why this contradicts newton’s model of the universe

Answer 12

• newton’s model states that universe is infinite and uniform
• so there must be a star along every line of light from earth making the sky bright at night
• but as there are regions without stars newton’s model is incorrect

Question 13

big bang model is consistent

Answer 13

• space and time originated with the big bang
• universe is expanding
• due to expansion light from distant stars has not yet reached / or has been redshifted to infrared and is not visible

Question 14

observed redshift of light from many distant galaxies is explained

Answer 14

the universe is expanding

Question 15

lendamaxT and big bang model

relationship between those two
or how does lenda max supports big bang theory

Answer 15

• the neutral temperature of the universe was very high after the big bang
• due to expansion and time, the temperature has now fallen to 2.7k

Question 16

experimental evidence that support big bang

Answer 16

• Hubble showed that galaxies are moving away from each other
• showing that the universe is expanding from an originated single point

Question 17

distinguish between solar system and galaxy

Answer 17

• a galaxy is much larger in size then a solar system
• a galaxy is more luminous
• a galaxy contains many solar systems

Question 18

distinguish between planet and comet

Answer 18

• a comet is a small icy body whereas a planet is made of rock and gas
• comets have larger orbits then planets
• comets often have tails, planets do not

Question 19

main sequence star

Answer 19

• absorption lines in the spectrum correspond to the h emission spectrum
• main sequence stars are rich in hydrogen

Question 20

radius of a white dwarf reaches a stable value

Answer 20

• the star collapses until gravitational force inwards is balance by electron degeneracy pressure outwards

Question 21

international collaboration has helped to refine this value

Answer 21

• data collection is expensive so cost can be shared
• data from around the world can be collected

Question 22

main sequence star are in equilibrium under the action of forces - equilibrium is achieved

Answer 22

• gravitational force inwards balanced by radiation pressure outwards

Question 23

star from main sequence to final stable phase

Answer 23

• main sequence to red giant
• the planetary nebula carries a core of mass <1.4mo
• so becomes a white dwarf

Question 24

hubble’s law assumption

Answer 24

rate of expansion of universe has been constant
- universe expand at a constant rate

Question 25

constellation / cluster

Answer 25

- stars in a cluster are close together, these in a constellation are not - stars in a cluster are held together by gravity, those in a constellation are not - stars in a cluster are the same age these in a constellation are not

Question 26

composition of star can be determined

Answer 26

- absorption spectrum of the star is observed - absorption line give an indication of the elements that make up the star

Question 27

main sequence to final stage

Answer 27

red giant -> planetary -> white dwarf

Question 28

Hubble measured the recessional velocity of galaxies

Answer 28

measured the redshift of the galaxies used z = v/c to find v

Question 29

prevents star from collapsing further

Answer 29

electron degeneracy pressure

Question 30

origin of EM radiation

Answer 30

thermal energy

Question 31

red shift

Answer 31

observed wavelength is greater than that emitted

Question 32

CMB evidence for big bang model

Answer 32

- the CMB comes from all regions of space it is uniform - the wavelength of the CMB matches that predicted by coding of the universe after the big bang / or by expansion of the universe - coding the wavelength of CMB matches the prediction that universe is expanding

Question 33

observation of spectra from distant galaxies provide evidence that the universe is expanding

Answer 33

distant galaxies have their spectra red shifted

Question 34

sun become a red giant

Answer 34

- fusion of hydrogen in the core stops and the core contract helium fusion now begins in the core causing the sun to expand and become more luminous.

Question 35

sun maintain a constant radius after it becomes a white dwarf

Answer 35

electron degeneracy pressure prevents further contraction

Question 36

light spectra of distant galaxies confirm hypotheses about the expansion of the universe

Answer 36

- spectra are redshifted - galaxies are moving away from us

Question 37

Hubble unlikely to predict the age of the universe

Answer 37

assumes the universe has a constant rate of expansion there is uncertainty in the value of Ho

Question 38

asteroids

Answer 38

lump rock between mars and Jupiter in the asteroid belt