Chapter 13 Exploring Our Galaxy. Our Location in the Milky Way. The Milky Way Galaxy is a disk-shaped collection of stars. Views of the Milky Way. When we look out at the night sky in the plane of the disk, the stars appear as a band of light that stretches all the way around the sky.
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Exploring Our Galaxy
The Milky Way Galaxy is a disk-shaped collection of stars.
The galaxy in this visible-light image is the Milky Way’s near-twin NGC 7331.
The same is true for this galaxy, NGC 1309, which has a similar structure to the Milky Way Galaxy and happens to be oriented face-on to us.
This image was made by mapping the sky with radio telescopes tuned to the 21-cm wavelength emitted by neutral interstellar hydrogen (H I). Black and blue represent the weakest emission, and red and white the strongest.
Details in the blank, wedge-shaped region at the bottom of the map are unknown. Gas in this part of the Galaxy is moving perpendicular to our line of sight and thus does not exhibit a detectable Doppler shift.
Perhaps, the spiral arms of the galaxy are a pattern that moves through the Galaxy, like ripples in water.