11.1 continued...
Characteristics of Stars
REVIEW: STAR TYPES
Guess which star type it is… !!
1.
2.
3.
4.
5.
6.
REVIEW: STAR TYPES
The answers…
1. Red Giants and Super Giants
2. Black Hole
3. White Dwarf Star
4. Supernova
5. Neutron Star
6. Main Sequence Star
Star Life Cycles
• Astronomers hypothesize that
stars change form over time,
progressing through stages
• These stages are shown well
on a famous diagram called the
Hertzsprung-Russell diagram
• It plots the different star
types on a graph according to
their luminosity (brightness)
and temperature
• 90% of stars in the sky are
thought to be on the main
sequence band
• Older stars are off the band
(giants, supergiants, and white
dwarfs)
Add labels to the diagram in your notes...
Add labels to the diagram in your notes...
Add labels to the diagram in your notes...
Add labels to the diagram in your notes...
Add labels to the diagram in your notes...
Add labels to the diagram in your notes...
Add labels to the diagram in your notes...
Some stars you may know, put on the
Hertzprung-Russell diagram...
3 Star Characteristics
that we can determine
1. A star’s composition
• Composition = what it’s made of
• Scientists can determine what elements of the periodic table
make up the outer atmosphere of a star
• REVIEW:
Done by looking at a star’s spectrum through a spectroscope
– The black lines in the spectrum are due to gases in the outer atmosphere of
the star absorbing some wavelengths of light as the light leaves the star
- Each element in the periodic table absorbs different
wavelengths from the spectrum
- Studying the pattern of black lines, scientists can deduce
which elements must be present
Most common element
in stars
2nd most common
element
2. A star’s temperature
• Determined by star`s colour
• Red = cool
– E.g., 3000 degrees Celcius
• Blue = hot
– E.g., 20 000 - 35 000 degrees
Celcius
• Other colours are
temperatures in between
– E.g., Our yellow Sun is 6000
degrees Celcius
• The relationship between
temperature and colour is
shown on the HertzsprungRussell diagram
Stars may look the same colour, but upon
closer inspection, they`re not!
Orion
Betelgeuse in top left corner (“armpit”)
Blue = hottest surface
temperature
Red = coolest surface
temperature
3. A star’s motion
REVIEW:
• Determined by a
shift in the black
lines of the star`s
spectrum
– Red shift = star
moving away from
Earth
– Blue shift = star
moving towards
Earth
The Doppler Effect
• Doppler Effect =
The phenomenon of
waves squishing or
stretching depending on
whether the wavemaking object is
moving toward or away
from an observer
http://www.youtube.com/watch?v=Kg9F5pN5tlI
http://science.howstuffworks.com/27963-assignmentdiscovery-doppler-effect-video.htm
Summary:
Scientists, with complicated computer programs,
try to interpret the light from stars to interpret their
composition, temperature, and direction of motion.
It’s not easy to get all that from one spectrum!