Revision Flashcards
Give formula for finding whether a star dims or gets brighter. Explain how it works.
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.
If the apparent magnitude of a star at 3.6pc is 14.7, how do we find the absolute magitude. Explain how formula works.
m - M = 5log(d) - 5
where d is the distance in pc
M is the absolute magnitude
m is the apparent magnitude
Steffan bozeman law.
F = sigma * T^4
Three formula for stars.
L = 4 * Pi * R^2 * sigma * T^4
L = 4 * Pi * d^2 * b
d = 1 / p
How do we calculate semi-major axis when we have perihelion and aphelion?
average distance.
Formula for doppler shift with wavelength.
λ ′ =λ(1− (observed speed / speed of light))
)
Redshift Formula
z = (lambda observed - lambda) / lambda
Formula for distance to a galaxy using hubble’s constant.
v = z * c
H0 = v / d
Arcminutes in degrees.
1 / 60th
Differentiate between doppler shift and cosmological redshift.
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.
Outline 3 differences between explosive nuclear processes involving white
dwarfs and those involving neutron stars.
- In novae, a runaway thermonuclear reaction occurs when hydrogen is ignited.
Helium ignites on neutron star surface in XRB. - In novae, visible and ultraviolet emitted. X-ray in XRB.
- White dwarf can also have supernova type 1a, if the thermonuclear reaction takes place in the core. Neutron stars cannot lead to supernova.
