star classification

color and temperature

Think about how the color of a piece of metal changes with temperature. A coil of an electric stove will start out black, but with added heat will start to glow a dull red. With more heat, the coil turns a brighter red, then orange. At extremely high temperatures the coil will turn yellow-white, or even blue-white (its hard to imagine a stove coil getting that hot). A stars color is also determined by the temperature of the stars surface. Relatively cool stars are red, warmer stars are orange or yellow, and extremely hot stars are blue or blue-white (Figure 1.1).

textbook_image

classifying stars by color

Color is the most common way to classify stars. Table 1.1 shows the classification system. The class of a star is given by a letter. Each letter corresponds to a color, and also to a range of temperatures. Note that these letters dont match the color names; they are left over from an older system that is no longer used. Class O B A F G K M Color Blue Blue-white White Yellowish-white Yellow Orange Red Temperature Range 30,000 K or more 10,000-30,000 K 7,500-10,000 K 6,000-7,500 K 5,500-6,000 K 3,500-5,000 K 2,000-3,500 K Sample Star Zeta Ophiuchi Rigel Altair Procyon A Sun Epsilon Indi Betelgeuse, Proxima Cen- tauri For most stars, surface temperature is also related to size. Bigger stars produce more energy, so their surfaces are hotter. Click image to the left or use the URL below. URL: Click image to the left or use the URL below. URL:

instructional diagrams

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questions

orions belt consists of stars that are different colors.

-->  a) true

b) false

betelgeuse, in the upper left of orions belt, is a __.

a) bright, blue, very hot star

b) yellow star like our sun

-->  c) bright, red, fairly cool star

d) white dwarf

extremely high temperature stars are ____.

a) red

b) orange

c) yellow

-->  d) blue

class m stars are __.

-->  a) red

b) orange

c) yellow

d) blue

stars are classified primarily by their

a) size

b) temperature

c) distance

-->  d) color

our sun is a __.

-->  a) yellow star

b) blue star

c) orange star

d) red star

the brighter the star, the larger it is.

-->  a) true

b) false

the main sequence stars

a) are white dwarfs.

-->  b) range from large, blue to small, red

c) range from white to red supergiants.

d) include all the stars in the universe.

the hertzsprung-russell diagram shows ___.

a) the distance and temperature of a star

b) the temperature and classification of a star

-->  c) the brightness and temperature of a star

d) the distance and brightness of a star

the brightest stars are more than 10,000 times brighter than the sun.

-->  a) true

b) false

diagram questions

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