The document discusses the Doppler effect and how it allows astronomers to measure the motion of stars and galaxies relative to Earth. A shift toward the red indicates the galaxy is moving away from Earth, a shift toward the blue means it is approaching, and no shift means it is at rest. It also briefly mentions that images from different types of telescopes like ultraviolet, infrared, and X-ray look very different and describes how spectrographs use prisms and gratings to split light into its spectrum.

1. DOPPLER EFFECT/SHIFT

2. Doppler shift
 Allows astronomers to measure the direction
of movement of stars and galaxies in relation
to Earth.

4.
1 No shift in the
spectral lines: The
galaxy is at rest
2 A shift toward the
red: The galaxy is
moving away.
3 A shift toward the
blue: The galaxy is
approaching Earth.

6. And…..
the images from the different
types of telescopes look very
different!

7. The images look very different
Ultraviolet
Infrared
NGC1512
barred spiral
galaxy
HST images

8. The images look very different
M87 giant elliptical galaxy in Virgo cluster

9. The images look very different
red=xray
green=optical
blue=UV
30 Doradus
Open cluster
in LMC

10. Spectrographs
 We don’t always want to make an image
 Sometimes, we want to split the light into its
spectrum
 We use spectrographs for this

11. Spectrographs
 There are two basic types of spectrographs
 Prisms
 Gratings
 Combining the two, we get Grisms

12. Prisms

13. Prisms
 Prisms work because light of different
wavelengths takes a slightly different path
 Comes out at a different place, and is thus
spread out

14. Gratings

15. Gratings
 Gratings are made up of hundreds or
thousands of tiny grooves
 They use a phenomenon of light known as
diffraction to split the light