Exam flashcards

Question 1

What is the Hill sphere?

Answer 1

The approximate sphere of influence around a planet where the object’s gravitational influence dominates that of the primary object

Question 2

What is the equation for a solar day?

Answer 2

1/P_solar = 1/P_sidereal - 1/P_orbit

Question 3

What is the sidereal day?

Answer 3

The spin period of rotation

Question 4

What is the equation for the orbital peirod?

Answer 4

(P_orbit/1yr)² = (a/1au)³

Question 5

What are the masses in the Hill sphere equation?

Answer 5

The masses of the two objects

Question 6

What are the densities in the Roche limit?

Answer 6

That of the planet/star and of the object orbiting

Question 7

When does a body spiral in at the Roche limit?

Answer 7

When the orbital angular is smaller than needed to synchronise rotation

Question 8

What is the origin of the moons of Mars?

Answer 8

Tidally captured asteroids

Question 9

What are the equations for governing plasma conditions?

Answer 9

Saha, gives ionisation equilibrium
Boltzmann, gives excitation equilibrium

Question 10

What are the processes contributing to absorption of photons?

Answer 10

Electron scattering
Free-free absorption
Bound-free absorption
Bound-bound absorption

Question 11

What is the equation for parallax?

Answer 11

d = 1/π

Question 12

What is a white dawrf?

Answer 12

A class star, much smaller than Sun

Question 13

What is a brown dwarf?

Answer 13

Very cool and very small

Question 14

What does a blue shift mean?

Answer 14

The star is travelling towards Earth

Question 15

What caused the change in definition of a planet?

Answer 15

Multiple discoveries of Pluto-like objects in the Kuiper belt

Question 16

Why do Venus and Mercury have no moons?

Answer 16

Overlap of Hill spheres and Roche limits cause moons to spiral in

Question 17

What are the assumptions for the gas giant internal structure?

Answer 17

Hydrostatic equilibrium
Mass conservation
Associating pressure with density

Question 18

What is the ratio of the Earth and Moon densities?

Answer 18

~1

Question 19

What is the Albedo for Venus?

Answer 19

0.76

Question 20

What is the perihelion?

Answer 20

Closest distance to sun
a(1-e)

Question 21

What is the aphelion?

Answer 21

Furthest distance from Sun
a(1+e)

Question 22

What is the assumption for finding the radius of a planet?

Answer 22

Set the density function to 0
sin(kr) = 0

Question 23

What are the main features of Jupiter in visible light?

Answer 23

Horizontal bands of dark zones and bright spots
Come from global convection

Question 24

What are the features of Jupiter in infrared?

Answer 24

Bright and dark regions reversed
Can see to greater depth and higher temperatures

Question 25

How is the mass loss of the Sun found?

Answer 25

dM/dt = ρdV = n_pm_p(4πr² v)

Question 26

How is the mass loss for a planet calculated?

Answer 26

Associate the grav pot energy with Luminosity in L = 1/2 n_pm_pv²πR² L_G=GMm/R And scaling with 1/d²

Question 27

What is the evidence of water on mars?

Answer 27

Abundance of deuterium Evidence of erosion features Spectroscopy reveals sedimentary rocks

Question 28

What are the sources of opacity in the solar atmosphere?

Answer 28

Bound-bound Bound-free Free-free Electron scattering

Question 29

What does LTE mean?

Answer 29

The source function is the Planck function S=B

Question 30

What does a cold gas mean?

Answer 30

Source function is zero S = 0

Question 31

How is a star gravitationally bound?

Answer 31

E = -U E is negative so star is bound

Question 32

What are the stages associated with each timescale?

Answer 32

Thermal-star formation Nuclear-Main sequence Gravitational-Star collapse

Question 33

At what range are white dwarfs formed?

Answer 33

M ≤ 8-10 solar masses

Question 34

How does temperature affect a blackbody spectrum?

Answer 34

Higher T gives a higher peak and more narrow distribution

Question 35

What is the equation for radiance?

Answer 35

σT⁴/π

Question 36

How do Balmer lines change?

Answer 36

Narrower for supergiant compared to main sequence

Question 37

How is the age of a star cluster estimated?

Answer 37

Location of the main sequence turn off point Isochrone fitting from stellar evolution models

Question 38

What is the PP1 chain?

Answer 38

2 H to D(Deuterium) plus positron plus neutrino D + H to He (3,2) plus gamma ray He (3,2) + He(3,2) to He (4,2) + 2H

Question 39

What is the centre of mass for a two body system?

Answer 39

a₁M₁ = a₂M₂

Question 40

What is the thermal luminosity of a planet?

Answer 40

L = 4πR_p²σT⁴