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.
Magnetic Interactions in the Hydrogen Atom
The Sky at 21 Centimeters
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.
Detecting Our Galaxy’s Spiral Arms
Neutral Hydrogen in Our Galaxy
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.
A Spiral Galaxy in Multiple Wavelengths
The Spiral Arms
The Rotation of the Milky Way
The Sun’s Orbit and the Mass of the Galaxy
Rotation Curves and the Mystery of Dark Matter
The Galaxy and Its Dark Matter Halo
Dark Matter Speculations
The Density-Wave Model
Perhaps, the spiral arms of the galaxy are a pattern that moves through the Galaxy, like ripples in water.
Star Formation in the Density-Wave Model
Infrared and Radio Observations of the Galactic Nucleus
X rays from around a Supermassive Black Hole