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14 Cards in this Set

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=apparent shift of nearby objects relative to background objects, due to changing perspective of observer

closer the object=greater the shift

smaller the angle, the larger the distance

closest star to us
Proxima Centauri in the Alpha Centauri star system

4.3 ly away
stellar motions
radial motion= motion towards or away from Earth (detected thru doppler shifts in light)

Transverse motion= motion across our line of sight
proper motion: angular motion of a star across line of sight
barnard's star
moved 228 ft in 22 years
proper motion of 10.3 ft/yr
energy emitted by an object in a unit amount of time

intrinsic propert= does not depend on observers location or motion relative to star
=apparent brightness

energy per unit area perpendicular to path of light at Earth (intensity of light)

not intrinsic. closer you are to object, the brighter it will appear
flux related to distance
@1 pc away, light pass thru 1 unit area
@ 2 pc away, same amount of light passes thru 4 unit area (each unit recieves 1/4 as much energy)
@3 pc away, same amount of light passes thru 9 unit area (each area reieves 1/9 as much energy)

f~1/ d^2
inverse square of light
flux directly related to luminosity (more luminous, brighter it will appear)

Flux inversely related to distance, squared (farther the star, the dimmer it will appear)

..if we know flux and distance, can measure lumionsity
magnitude scale
hipparchus: compared brightness of stars and ranked them. brightest=1st class, faintest=6th class

apparent visual magnitude: brighter the star, the lower the magnitude. possible for negative magnitude.
decrease of 5=increase in flux by factor of 100
absolute v. apparent magnitude
absolute= intrinsic visual magnitude of a star (analogous to luminosity). property of a star, will not change regardless of distance or motion

apparent= visual magnitude of a star as it appears from Earth (analogous to Earth). would change if start were moved to different location

apparent=absolute if star located 10 pc away
cool star: more yellow light than blue

warm star: rougly equal amounts of blue and yellow light

hot star: more blue light than yellow
Hydrogen Balmer lines
A stars= strongest Balmer lines

Q stars= weakest Balmer lines
spectral classification

O= hottest
M= coolest

10 subclasses (0-9; 0 is slightly hotter, 9 is slightly cooler)

sun is G2
HR diagram
white dwarfs= hotter, lower luminosity stars

red giants= cool, red stars with high luminosity