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¨  Star color and Temp ¡  The color of the star gives you an idea of how hot it

burns ¡  Stars that burn above 30,000 K emit short

wavelengths and appear blue ¡  Stars between 5000 to 6000 K appear yellow

(medium wavelengths) ¡  Red stars are cooler and emit longer wavelengths

¨  Binary Stars and Stellar Mass ¡  Binary stars are stars that orbit each other

ú  Used to calculate star’s mass ú  Mass is determined by knowing the distance to the

center of mass between the two stars and dividing how long it takes to orbit in years

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¨  Parallax- a slight shifting in the apparent position of a nearby star caused by the orbit of the Earth

¨  Parallax angles are extremely small and require

precise instruments to measure changes. ¨  Light-year- distance light travels in a year

(9.5 x 1012 km or 5.8 trillion miles)

¨  Stars should appear just white because they give all light

¨  Color differences appear because of thin transparent layers the light has to pass through

¨  Color is determined by temperature and composition. ¨  The color classifications are:

¡  O- Blue ¡  B- White-Blue ¡  A- White ¡  F- Yellow-White ¡  G-Yellow ¡  K- Yellow-Orange ¡  M- Red

¨  How bright a star is correlates with the size of the star

¨  Classification is in Roman Numerals ¡  I- Supergiant ¡  II- Bright Giants ¡  III- Giants ¡  IV- Subgiants ¡  V- Main Sequence (Dwarf) ¡  VI- Subdwarf ¡  VII- White Dwarfs

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¨  Apparent Magnitude ¡  The brightness as it appears looking at it from Earth ¡  3 Factors determine brightness

ú  Size ú  Temperature ú  Distance

¡  The larger the number is the dimmer the star ¡  Ex. Sun= -26.7

¨  Absolute Magnitude ¡  The stars brightness determined if it were 32.6 LY away. ¡  Ex. Sun= 5

¨  Shows relationship between absolute magnitude and temperature

¨  Stars that fluctuate from bright to faint are called Cepheid variables

¨  A light period is the time between two consecutive occurrences of maximum brightness

¨  Novas ¡  A sudden brightening due to the high speed ejection

of the outer layer of the star ¡  Star only lose small amounts of matter when

eruptions occur

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¨  The space between stars has clouds of dust and gases called nebulae

¨  Nebulae glow when heated by a star ¨  Two types of bright nebulae

¡  Emission- mostly hydrogen gas which absorb UV light and convert it to visible light. ú  Process of conversion is called florescence

¡  Reflection- reflect light from nearby stars ú  Dense clouds of interstellar dust

¨  Nebulae not close enough to stars are called dark nebulae