ASTR Midterm 1
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Given distance to object and object's disk in degree
Asked to find diameter of object
convert degree to arcsec

Given semimajor axis of object orbiting the Sun
Asked to find sidereal period
 Semimajor axis must be in AU
 sidereal period in seconds

Given objects length (diameter) and angle it subtends
Asked to find distance to object
angle in arcsec

Given mass of object (or ratio of mass) and semimajor axis
Asked to find gravitational force
Mass in kg and radius in meters

Given force and object's mass
Asked to find acceleration
acceleration in meters/second

Given sidereal period and semimajor axis of exoplanet
Asked to find mass of star (allowed to assume mass of planet is negligible)
 a (semimajor axis) in meters
 P (sidereal period) in seconds

Given objects distance from Sun and perihelion and aphelion
Asked to find sidereal period
 sidereal period in seconds
 semimajor axis in AU

Given perihelion and aphelion
Asked to find eccentricity of object's orbit
e ⋅ a= semimajor axis  perihelion
a is semimajor axis in AU

Given exoplanet's mass and diameter
Asked to determine weight on planet
 weight is force
 most likely asked to compare and set up ratio

Given surface temperature star
Asked to wavelength star radiates the most energy
λ in meter

Given surface temperature and radius of star
Asked to find luminosity
L=4⋅(pi)⋅R²⋅σ⋅T^{4}
R in meters

Given frequency of wave
Asked to find wavelenght

Given wavelength of wave or photon
Asked to find energy of wave or photon

Given frequency of wave or photon
Asked to find energy of wave of photon

Given semimajor axis and period of planetary satellite
Asked to find mass of planet (not satellite)

Given stellar luminosity and semimajor of orbiting planet
Asked to find flux of star at planet
 L in watts
 d in meters
 F in W/m^{2}

Given observed wavelength and laboratory wavelength
Asked to determine is star is moving toward or away from observer
Δλ=λ
_{observed}  λ
_{laboratory}
 Δλ is positive it is a redshift (moving away)
 Δλ is negative it is a blueshift (moving toward)

Given observed and laboratory wavelengths
Asked to determine velocity

Given diameter of telescope
Asked to find light gathering power
light gathering power = d^{2 }

Given diameter of telescope and wavelength of light
Asked to find resolving power
θ=2.5×10
^{5} (λ÷D)
 θ in arcsec
 λ in meters
 D in meters

Given resolving power of telescope and distance to observable object
Asked to determine size of smallest features the telescope can resolve
α in arcsec

Given surface temperature
Asked to find flux
F = σT^{4
}F in W/m^{2}

Given energy of wave or photon
Asked to find wavelength

Given luminosity and % mass converted to energy
Asked to determine mass that is converted to maintain luminosity
Three parts:
 Part one: Luminosity is measured in W which = J/s (convert is needed or just make connection)
 Part Two:
 Part Three: divide mass of part two by % mass

Given parallax
Asked to determine distance from us

Given distance and proper motion
Asked to find tangential velocity
v
_{t} = 4.74μd
 μ in arcsec per year
 d in km
 v_{t} in km/s

Given observed and laboratory wavelength
Asked to find radial velocity

Given radial velocity and tangential velocity
Asked to find space velocity

Given apparent brightness compared to Sun's and distance
Asked to find luminosity of star

Given star's distance and comparative brightness to star seen without telescope
Asked for distance to be seen without telescope

Given apparent magnitude of star and two telescope diameters
Asked to determine magnitude of dimmest star seen through larger telescope
Two Parts:
 Part One: Compare light gathering power to get ratio of brightness between viewed stars
 Part Two:


Given apparent magnitude and parallax
Two parts:
 Part One:
 Part Two:

Given absolute magnitude of star (star_{1}) and a ratio of luminosity
Asked to find absolute magnitude of another star (star_{2})

Given apparent magnitude and absolute magnitude
Asked to find distance to star

Given semimajor axis and sidereal period of binary star system
Asked to find sum of masses of two stars
Masses in solar mass

Given age of star cluster
Asked to find mass of turn off star