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Transcript
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
2. Tells us if galaxies and stars are moving
away from us or toward us
There are 3 kinds of visible spectra:
Continuous, bright-line and dark-line.
Continuous – unbroken band of colors
from a source sending out all visible
wavelengths.
Bright-line spectrum – also called an
emission spectrum, is a series of
unevenly spaced lines of different
colors and brightness.
Hydrogen emission spectrum
Every element has its own unique
bright-line spectrum, like a fingerprint.
Helium emission spectrum
Dark-line spectrum – a continuous
spectrum with dark lines where light has
been absorbed. (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