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Stellar
Characteristics
Temperature
•Temp. is measured in Kelvins
•Blue stars are hot, above
30,000 K
•Yellow stars are warm
•Red stars are cool, below
3,000 K
Star streaks (4 hr time-lapse)
...there ARE different color stars!
Mass
• Size can be small, medium or
massive
• Binary Stars: when two stars orbit
around each other
• Stars of equal mass have their
center of mass in the middle
to stabilize the teeter totter, the center of
mass has to be closer to the big kid
if astronomers see the two stars orbiting like this, it helps
them determine which star is bigger
Distance
• Parallax used for nearby stars
• the inverse square law of light
is used for distant stars
• Light year = 9.5 trillion km
• Parsec = 3.3 light years
Parallax
Magnitude
•Magnitude = brightness
•apparent magnitude: star’s
brightness as it appears to us
•absolute magnitude: how bright
a star actually is
•Bright stars are negative and
dim stars are positive
which star is the brightest?
Chemical Composition
•The elements a star is made
of
•Each element has a unique
spectral line, like a fingerprint
Emission spectrum of Hydrogen, H
Emission spectrum of Iron, Fe
#1What does a Kelvin
measure?
• star’s name
• star’s brightness
• star’s composition
• star’s temperature
• star’s temperature
#2 Order the stars from
coolest to hottest
•
•
yellow - blue - red?
answer: red - yellow - blue
#3 It is hard to
measure the size of a
star, but what can we
use to help?
• Binary star system
• Binomial star system
• light year
• parallax
• Binary star system
#4 Dim or Bright?
• Compare the following absolute
magnitudes:
• -2 absolute magnitude :
• 10 absolute magnitude :