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 = 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 Magnitude

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

#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 :