Astrophysics

Question 1

Define planet:

Answer 1

an object with sufficient mass for its own gravity to make it spherical and clear the orbit of other objects

Question 2

Define dwarf planet:

Answer 2

orbit not cleared of other objects

Question 3

What are planetary satellites?

Answer 3

bodies that orbit a planet

Question 4

What are asteroids?

Answer 4

objects that are too small and uneven to be planets, near circular orbit to sun

Question 5

What are comets?

Answer 5

small, irregular sized balls of rock, dust, and ice; have an eccentric elliptical orbit around the sun

Question 6

What are solar systems?

Answer 6

group of stars and orbiting objects

Question 7

What are galaxies?

Answer 7

collection of stars (around 100 billion), dust and gas

Question 8

What is the doppler effect?

Answer 8

apparent shift in wavelength occurring when the source of the wavelength is moving

Question 9

What happens to the wavelengths according to the doppler effect?

Answer 9

wavelength emitted remains the same, wavelength received changes

Question 10

What is the formation of a small star?

Answer 10

nebula > protostar > main sequence > red giant > white dwarf > black dwarf

Question 11

What is the formation of a large star?

Answer 11

nebula > protostar > main sequence> super red giant > supernova > (supermassive) black hole/ neutron star

Question 12

Which pressures are balanced in main sequence?

Answer 12

gravitational and radiation

Question 13

How heavy is a star for it to be a large star?

Answer 13

greater than 10 mass units

Question 14

How heavy is a star for it to be a small star?

Answer 14

between 0.5 to 10 mass units

Question 15

When can electrons bound to an atom exist?

Answer 15

in certain energy levels

Question 16

What is needed when moving an electron to a higher energy level?

Answer 16

external energy (heat/ absorbing a photon)

Question 17

What happens when an electron moves to a lower energy level?

Answer 17

releases a photon with specific wavelength

Question 18

What is the lowest energy level?

Answer 18

ground state

Question 19

What is the energy of an electron free of an atom?

Answer 19

0J

Question 20

Why is energy change between levels negative?

Answer 20

it is the energy required to remove the electron from the atom

Question 21

What is Wein’s law?

Answer 21

the black body radiation curve for different temperatures peaks at a wavelength inversely proportional to the temperature of the object

Question 22

What does the peak of Wein’s graph represent?

Answer 22

temperature

Question 23

What does the x axis of Wein’s graph represent?

Answer 23

wavelength

Question 24

What is Stephan’s Law?

Answer 24

radiant heat energy emitted from a surface is proportional to temperature^4

Question 25

List light years, parsecs and astronomical units in smallest to largest:

Answer 25

astronomical units, light years, parsecs

Question 26

What unit is a parallax angle measured in?

Answer 26

arcsec

Question 27

What are parallax angles used to find?

Answer 27

unknown distances that stars are away

Question 28

What is the cosmological principle?

Answer 28

the universe is isotropic and homogenous and the laws of physics are universal

Question 29

What does isotropic mean?

Answer 29

same in all directions

Question 30

What does homogenous mean?

Answer 30

matter is universally distributed

Question 31

What is Hubble's law?

Answer 31

recessional velocity of a galaxy is proportional to it's distance from the earth

Question 32

What does Hubble's law show?

Answer 32

the universe is expanding and distance from galaxies are redshifted (moving away from earth)

Question 33

What is the big bang theory?

Answer 33

all objects were initially a singularity

Question 34

What is the evidence for the big bang?

Answer 34

Hubble's law (universe expanding) and background microwave radiation

Question 35

What happened in the evolution of the universe?

Answer 35

- Big Bang: time and space created - 10^-35s: inflation - 10^-6s: fundemental particles gain mass - 10^-3s: mass created via pair production (hadrons and leptons) - 1s: production of mass halted - 100s: protons and neutrons fuse - 380,000 years: first atom - 30 million: stars formed + fusion for heavier elements - 200 million: galaxies form and gravitational fields pull hydrogen and stars together - 9 billion: solar system formed - 10 billion: sun and earth formed - 11 billion: life on earth - 13.7 billion: humans

Question 36

What is dark matter?

Answer 36

hypothetical form of matter that fills space and accelerates expansion and shows there is no centre to the universe