Download Spectroscopy PPT

Spectroscopy:
and stars
Most of what is known about stars comes
from spectroscopy (or the study of
spectra).
Spectra (rainbows of diffracted light) can
come from a (hot) glowing solid, a glowing
liquid or a glowing gas (star).
2 astronomical purposes:
1. Tells us the elements
that make up galaxies
and stars (Every
element has its own
unique line spectrum,
like a fingerprint)
2. Tells us if galaxies and
stars are moving away
from us or toward us
(called?)
There are 3 kinds of visible spectra:
Continuous, bright-line and dark-line.
Continuous – unbroken band of colors
from a hot source.
Bright-line spectrum – also called an
emission spectrum, is seen when light
comes through a hot gas.
Hydrogen emission spectrum
Helium emission spectrum
Dark-line spectrum – seen when light
comes through a cold gas. (absorption
spectrum)
Helium absorption spectrum
The dark lines are in the exact same
place as the bright lines would be for the
same element in a bright-line spectrum.
The dark lines are formed when light
The lines tell us what gases are in the
atmospheres of stars.
Dark-line spectrum
Bright-line spectrum
Hydrogen emission spectrum
Stars’ (dark-line) spectra.
Blueshift
Redshift
Red shift: when the colors of the bright
line spectrum shift toward the red.
?Why important?: This means that
the star or galaxy is moving away from you.
Blue shift: when the colors of the bright
line spectrum shift toward the blue.
?Why important?: This means that
the star or galaxy is moving toward you.
What does the bumper sticker mean?
If the background on this bumper-sticker
appears blue, you’re going way too fast!
What you will see with spectroscope