Revision

Question 1

Give formula for finding whether a star dims or gets brighter. Explain how it works.

Answer 1

2.5log( F1 / F2)

F1 = initial flux / brightness
F2 = later flux / brightness

If output is negative star became brighter.
If output is positive star became
dimmer.

Question 2

If the apparent magnitude of a star at 3.6pc is 14.7, how do we find the absolute magitude. Explain how formula works.

Answer 2

m - M = 5log(d) - 5

where d is the distance in pc
M is the absolute magnitude
m is the apparent magnitude

Question 3

Steffan bozeman law.

Answer 3

F = sigma * T^4

Question 4

Three formula for stars.

Answer 4

L = 4 * Pi * R^2 * sigma * T^4
L = 4 * Pi * d^2 * b
d = 1 / p

Question 5

How do we calculate semi-major axis when we have perihelion and aphelion?

Answer 5

average distance.

Question 6

Formula for doppler shift with wavelength.

Answer 6

λ ′ =λ(1− (observed speed / speed of light))
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Question 7

Redshift Formula

Answer 7

z = (lambda observed - lambda) / lambda

Question 8

Formula for distance to a galaxy using hubble’s constant.

Answer 8

v = z * c
H0 = v / d

Question 9

Arcminutes in degrees.

Answer 9

1 / 60th

Question 10

Differentiate between doppler shift and cosmological redshift.

Answer 10

The apparent change in frequency (and hence wavelength) of a wave due to the relative motion between the source and the observer.

The increase in the wavelength of light from distant galaxies due to the expansion of the universe, caused by the stretching of space itself rather than the motion of the source.

Question 11

Outline 3 differences between explosive nuclear processes involving white
dwarfs and those involving neutron stars.

Answer 11

1. In novae, a runaway thermonuclear reaction occurs when hydrogen is ignited.
   Helium ignites on neutron star surface in XRB.
2. In novae, visible and ultraviolet emitted. X-ray in XRB.
3. White dwarf can also have supernova type 1a, if the thermonuclear reaction takes place in the core. Neutron stars cannot lead to supernova.

Question 12

Explain LIGO.

Answer 12

Laser Interferometer Gravitational Wave Observatory.

Two perpendicular arms 4km long each form an L shape.
A laser is split between the two arms, and reflected by mirrors at the end. The two lasers come back and recombine.
Any change in the distance of the arms due to spacetime distortion alters the interference pattern of the lasers.

Question 13

What is the relationship between gravitational waves and GRB?

Answer 13

Both are produced in cataclysmic universe events such as neutron star and black hole mergers. Gravitational waves occur as they merge, GRB occurs after.