Spectroscopy:

and finding out the elements of deep space objects

2 astronomical purposes:

• Tells us the elements that make up galaxies and stars

• Tells us if galaxies and stars are moving away from us or toward us

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).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.

Dark-line spectrum – a continuous spectrum with dark lines where light has been absorbed. (absorption spectrum)

Helium emission 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.

Stars’ (dark-line) spectra.

Dark-line spectrum

Bright-line spectrum

Blueshift

Redshift

Hydrogen emission spectrum

Red shift: when the colors of the bright line spectrum shift toward the red.

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.

This means that the star or galaxy is moving toward you.

The student will understand the similarities and differences between the three types of spectra.In addition, students will understand how spectra are used to learn about planets and stars.Materials - Low pressure gas discharge tubes, high voltage electrical exciter and spectroscopes.

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-stickerappears blue, you’re going way too fast!