stellar populations

stellar populations

stellar populations two broadly contrasting distributions of star types that are characteristic of different parts of a galaxy . Population I stars are young, recently formed stars, whereas population II stars are old and highly evolved. Population II stars are formed early in the history of the galaxy from pure hydrogen with an admixture of primordial helium. Because massive blue-white giants burn their nuclear fuel quickly and therefore have lifetimes of only a few million years, no stars of this type are found in population II. The most luminous population II stars are red giants. Population I stars, of which the sun is typical, are young stars that still lie mostly on the main sequence of the Hertzsprung-Russell diagram . The most luminous population I stars are blue giants. Because they are second-generation stars formed from the debris of exploded population II stars, population I stars have a considerable content of heavy elements that were created by nucleosynthesis in the interiors of the earlier stars. Population I and population II stars are both found in the spiral galaxies. Population I stars are located in the disk singly and in galactic, or open, star clusters . They are particularly concentrated in the interstellar dust of the spiral arms, where new stars are continually being formed. The very brightest population I stars are not distributed at random, but are grouped in loose associations of several hundred stars that partake in the general galactic rotation and are believed to have a common origin. Population II stars are found both in the spiral arms and in the gas-free and dust-free regions of the spiral galaxies, i.e., the nucleus and the halo of high-velocity stars and globular clusters that surround the disk of the galaxy. Irregular galaxies are predominantly, or sometimes exclusively, composed of population I stars. Elliptical galaxies, which lack spiral arms, are composed almost entirely of population II stars. The categories population I and population II were first introduced by Walter Baade as a result of his studies of the Andromeda Galaxy .

Show all research tools

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"stellar populations." The Columbia Encyclopedia, 6th ed.. 2008. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>.

"stellar populations." The Columbia Encyclopedia, 6th ed.. 2008. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1E1-stellarp.html

"stellar populations." The Columbia Encyclopedia, 6th ed.. 2008. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-stellarp.html

Learn more about citation styles

population, stellar

population, stellar A classification of stars on the basis of certain physical characteristics, such as their location in the Galaxy, the types of orbits they have around it, and their content of heavy elements. Each of these properties is believed to depend on the age of the Galaxy when the star formed, so that Population I, Population II, and Population III contain stars formed at progressively earlier epochs.

Show all research tools

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"population, stellar." A Dictionary of Astronomy. 1997. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>.

"population, stellar." A Dictionary of Astronomy. 1997. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O80-populationstellar.html

"population, stellar." A Dictionary of Astronomy. 1997. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O80-populationstellar.html

Learn more about citation styles

stellar population

stellar population See population, stellar.

Show all research tools

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"stellar population." A Dictionary of Astronomy. 1997. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>.

"stellar population." A Dictionary of Astronomy. 1997. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O80-stellarpopulation.html

"stellar population." A Dictionary of Astronomy. 1997. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O80-stellarpopulation.html

Learn more about citation styles

Free newspaper and magazine articles

Research and Markets: Stellar Populations: A User Guide from Low to High...
News Wire article from: M2 Presswire; 1/25/2012
Stellar populations; a user guide from low to high redshift.(Brief...
Magazine article from: Reference &amp; Research Book News; 12/1/2011
Galaxy wars; stellar populations and star formation in interacting galaxies;...
Magazine article from: SciTech Book News; 9/1/2010

Pictures from Google Image Search

Click to see an enlarged picture
Click to see an enlarged picture
Click to see an enlarged picture

See more pictures of stellar populations