Skip to main content

stellar structure

stellar structure, physical properties of a star and the processes taking place within it. Except for that of the sun, astronomers must draw their conclusions regarding stellar structure on the basis of light and other radiation from stars that are light-years away; this light enables them to observe only the stars' surfaces. Knowledge of the processes taking place in a star and of conditions within its interior must be inferred from the laws of physics and chemistry. A star is a nearly spherical body of incandescent gas, mostly hydrogen and helium. Because it is observed to be stable, astronomers can conclude that the inward pressure of gravitation holding the star together is balanced by the outward pressure due to the energy generated by the star, and that the rate at which energy is radiated away from the star's surface is equal to the rate at which it is produced in the interior. The most important properties of a star are its size, mass, luminosity, chemical composition, and the temperature, pressure, and density at all distances from its center to its surface. These last three properties are related by the gas laws; their values decrease with distance from the star's center. Stars vary widely in size and luminosity but have masses only within the range from about 0.08 to 100 times the mass of the sun, with few exceptions; less massive bodies cannot support the energy-producing processes of a star (see brown dwarf), while more massive bodies are generally unstable. An ordinary star has a surface temperature of thousands of degrees, implying central temperatures of millions of degrees. The central pressure and density are also extremely high, but the temperature is such that the material will still remain in the gaseous state. At these temperatures, energy is produced by thermonuclear fusion (see nuclear energy), in which two or more nuclei are fused to form a single heavier nucleus. As such fusion processes proceed within the star, its chemical composition necessarily changes, with heavier elements increasing at the expense of lighter elements (see nucleosynthesis). The mass and chemical composition of the star together determine all of its other properties, e.g., size, luminosity, and temperature. Astronomers can determine the temperature and chemical composition of the star's surface from analysis of the spectrum of light from the star. Such a spectrum consists of a continuous blackbody spectrum produced by complex conditions within the star superimposed on which is a series of dark lines due to absorption of energy by the cooler stellar atmosphere. From such observations much is learned about the other properties and conditions within the star and thus about its stage of stellar evolution.

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

  • MLA
  • Chicago
  • APA

"stellar structure." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 24 Oct. 2017 <http://www.encyclopedia.com>.

"stellar structure." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (October 24, 2017). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/stellar-structure

"stellar structure." The Columbia Encyclopedia, 6th ed.. . Retrieved October 24, 2017 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/stellar-structure

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.