Download Characteristics of Stars Stars Analyzing Starlight Star Characteristics

30.1 Characteristics of Stars
Characteristics of Stars
Section 30.1
Analyzing Starlight
· spectrographs - device that separates light into
different wavelengths (colors)
· each star produces a unique spectrum (series of
colors and lines)
· a star's spectrum tells us
elements present (composition)
surface temperature
how fast the star is moving
toward or away from Earth
Stars
· star = ball of gas that emits light
· fueled by nuclear fusion
· vary in color
Star Characteristics
· composition
most common element - hydrogen
second most common - helium
· temperature
blue = hottest
yellow (ex. sun)
red = coolest
· size and mass
dwarf, medium,
and giant
Solar spectrum
1 How do scientists determine the
composition and temperature of stars?
A
by taking samples from the star's surface
B
by analyzing the vibrations that the star emits
C
through magnetic testing
D
by analyzing the spectra of the light that a
star emits
2 What color are the warmest stars?
A
yellow
B
blue
C
white
D
red
30.1 Characteristics of Stars
Stellar Motion
· apparent
motion visible to the unaided eye
caused by Earth's rotation
appear to move counter-clockwise around Polaris
(the North Star)
different stars appear in different seasons
circumpolar stars - always visible in the night sky
Red Shift = star moving away
· actual
rotate on an axis
revolve around another star
move away from or toward our solar system
· Doppler effect
shifting wavelengths of light emitted by a light source
moving toward or away from an observer
blue shift = moving toward Earth
red shift = moving away from Earth
Distances to Stars
· light-year = distance light travels in one year
9.46 trillion km/year
sun = 8 light minutes away
Proxima Centauri = 4.2 light-years away
Polaris = 700 light-years away
· parallax = apparent shift in a star's
position when viewed from
different locations
accurate up to 1000
light-years
3 Why do stars appear to move in the
sky?
Blue shift = star moving toward
Stellar Brightness
· visibility of a star depends on brightness (magnitude)
and distance from Earth
1 = brightness stars
6 = faintest stars
· apparent magnitude = brightness of a star from
Earth
· absolute magnitude = how bright a star would be if
it were 32.6light-years from Earth
aka true brightness
compared against a standard
4 Scientists use parallax to determine
A
a star's distance
A
the sky is rotating
B
if the star is moving toward or away from Earth
B
the universe is expanding
C
the brightness of a star
C
Earth is moving
D
a star's actual motion
D
galaxies are forming