ASTR 105 Lecture Notes - Lecture 4: Formula Atlantic, Electric Light, Binary Star
Lab AST 105 Lecture Notes 4:
• parallax
• a method for finding distances based on the shift in an object's position caused by the
observer's motion
• parallax formula
• d=1/p
• where d=distance to the star in parsecs and p=parallax angle of the star in arc seconds
• Wein's Law
• a relation between a body's temperature and the wavelength at which it emits radiation
most intensely - hotter bodies radiate more intensely at shorter wavelengths
• Wein's Law formula
• T=(2.9x10^6 K nm)/(λ max)
• where T=temperature of the star in Kelvin and λmax=strongest emitted wavelength of
starlight in nanometers
• luminosity
• rate of energy production - the wattage of a lightbulb defines its luminosity - stellar
luminosity is usually measured in units of the Sun's luminosity (approx. 4x10^26 watts)
• brightness
• energy from light that falls on a surface at a distance - like our eyes or a telescope
• inverse-square law
• the apparent brightness of a body decreases inversely as the square of its distance
• inverse-square law formula
• B=(L)/(4π(d^2))
• where B=brightness of the star, d=distance to the star, and L=luminosity of the star - we
can use this to measure a star's luminosity
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