10: Interstellar Media
- Page ID
- 115284
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Sometimes, people can focus on the biggest and brightest objects and forget the importance of the little things. The universe is full of exciting objects like black holes and galaxies. At the same time, the gas and dust in between these objects has a lot to tell us about the universe.
- Describe how the interstellar medium is divided into gaseous and solid components
- List the major types of interstellar gas
- Explain the role and importance of infrared observations in studying dust
- Define the terms extinction and interstellar reddening
- Define cosmic rays and describe their composition
- Explain how dust grains help produce molecules that eventually find their way into planetary systems
- Describe how interstellar matter is arranged around the Solar System
- 10.2: Interstellar Gas and Dust
- Interstellar gas may be hot or cold. Gas found near hot stars emits light by fluorescence, that is, light is emitted when an electron is captured by an ion and cascades down to lower-energy levels. Most hydrogen in interstellar space is not ionized and can best be studied by radio measurements of the 21-centimeter line. Some of the gas in interstellar space is at a temperature of a million degrees, even though it is far away in hot stars.
- 10.3: Cosmic Materials
- Cosmic rays are particles that travel through interstellar space at a typical speed of 90% of the speed of light. The most abundant elements in cosmic rays are the nuclei of hydrogen and helium, but electrons and positrons are also found. It is likely that many cosmic rays are produced in supernova shocks.
- 10.4: Interstellar Matter around the Sun
- The Sun is located at the edge of a low-density cloud called the Local Fluff. The Sun and this cloud are located within the Local Bubble, a region extending to at least 300 light-years from the Sun, within which the density of interstellar material is extremely low. Astronomers think this bubble was blown by some nearby stars that experienced a strong wind and some supernova explosions.
Thumbnail: What looks much like craggy mountains on a moonlit evening is actually the edge of a nearby, young, star-forming region NGC 3324 in the Carina Nebula. Captured in infrared light by the Near-Infrared Camera (NIRCam) on NASA’s James Webb Space Telescope, this image reveals previously obscured areas of star birth. ("Cosmic Cliffs in the Carina Nebula," NASA, Public Domain via Wikimedia Commons)