Download Slide 1

Spectral Lines
Most of what is known about stars
comes from spectral studies.
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.
Continuous spectra can come from a
(hot) glowing solid, a glowing liquid or
a glowing gas (star). (DENSE)
Bright-line spectrum – also called an
emission spectrum, is a series of
unevenly spaced lines of different
colors and brightness. (LESS
DENSE)
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
passes through a cooler gas. The dark
lines tell us what gases are in the
atmospheres of stars and planets.
Dark-line spectrum
Bright-line spectrum
Hydrogen emission spectrum
Stars’ (dark-line) spectra.
Blueshift
Redshift
Here’s a Recap:
REMEMBER THIS:
Red Moves Ahead
Blue Comes To You
Some
examples of
element
“fingerprints”
Omega Nebula
1.What is a continuous spectrum?
2.What is a bright line spectrum?
3.What is a dark line spectrum?
4.What does the bumper sticker
mean?
If the background on this bumper-sticker
appears blue, you’re going way too fast!
Spectrum of the Periodic Table