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Interstellar Medium 2009

Page history last edited by Mariah W. 13 years, 3 months ago

What is the Interstellar Medium?

And how is it connected to everything else? 

by Mariah W.




The Interstellar Medium, also known as ISM, is the gas and dust that is spread throughout all of interstellar space.

  • ISM is made up of a highly dilute mixture of cosmic rays, ions, (galactic) magnetic fields, molecules, larger dust grains, and atoms.
  • Its matter consists of about one percent dust and ninety nine percent gas by mass.
  • The ISM has a very low density. 
  • Fifteen percent of the visible matter in the Milky Way is composed of interstellar gas and dust. 
  • Within the densest regions of the ISM  stars are formed.
  • The ISM is replenished with matter and energy through supernovae, planetary nebular, and stellar winds (see diagram bellow).
  • Breaking Down the words:
  1. "Interstellar" - The word interstellar consists of two main prefixes, "inter-" which is means among, between, or amid and "-stellar" which means of or pertaining to stars or full stars. When combined the definition of interstellar is between or among the stars.
  2. "Medium" - A medium is something that lies between or in the middle of things. It can also mean a substance through which an effect is transmitted from one thing or another. For example, when one speaks the waves of sound are carried by the air so the air is the medium through which sound travels! 
  3. Putting it together - The interstellar medium is the material which is found between the stars.   


Image credit: www.strw.leidenuniv.nl/~woitke/Bilder/Cycle_of_matter_small.jpg


When the interstellar dust forms a cloud with hydrogen gas and plasma it forms a nebula.



A Nebula is an interstellar cloud of dust, hydrogen gas and plasma!

Nebulae can form star-forming regions in which dust, gas, and other materials clump together. These formations attract more matter and eventually become large enough to form stars and planets (as well as other planetary systems and objects)!


                                                 The Triangulum Emission Nebula NGC 604                                                                           The Cat's Eye Nebula,

                                                                                                                                                                                      an example of a planetary nebula.




Astronomers and Physicists are the ones who are most interested in learning about the interstellar medium at present. In the past there were many other people who contributed to the study of the IMS, like scientists and naturalists.


What new studies are there?


The Interstellar Probe


Image Credit: interstellar.jpl.nasa.gov/


The Interstellar Probe mission has been proposed in order to begin the exploration of the local galactic vicinity. Since interstellar space is still a largely unknown "frontier" that holds many keys to understanding Earth's, and our, place in the galaxy it will be one of the grand scientific enterprises of the next century! A bubble called the heliosphere, that is created by the rapidly expanding solar atmosphere (the solar wind), that shields our solar system from the interstellar plasma and magnetic fields, and most of the cosmic rays and dust that comprise the local galactic neighborhood. The (proposed) Interstellar Probe mission is designed to exit this bubble and begin exploring the space between the stars (interstellar space). In the course of its passage through space the probe will investigate unknown aspects of the outer solar system, explore the boundaries of the heliosphere to reveal how a star interacts with its environment, and directly sample the properties of the heliosphere to reveal how a star interacts with its environment, and directly sample the properties of the nearby interstellar medium!  




Interstellar: situated or occurring between the stars. 

The Interstellar Medium: (or ISM) is the gas and dust that spreads throughout all interstellar space. 

Interstellar Space: is the matter that exists between the stars that are within a galaxy.

Interstellar Dust: is dust that is found between the stars


Sources and Links: 










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