The Physics
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Mass Needed to Create a Neutron Star

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Bibliographic Entry Result
(w/surrounding text)
Holton, Gerald & Roller, Dance. Modern Physical Science. Boston: Addison-Wesley, 1984: 153. "If a star is about 1.5 solar masses, the resulting object formed would be a neutron star." 1.5 solar masses
World Book Encyclopedia. Chicago: World Book, 1996: 155. "a mass between 1.4 and 3.0 solar masses" 1.4–3.0 solar masses
Clark, Stuart. Stars and Atoms. New York: Oxford University Press, 1995: 128. "They contain more than 1.5 solar masses" 1.5 solar masses
Degani, Meir H. Astronomy Made Simple. New York: Doubleday, 1976: 100. "A neutron star is less than 3.2 solar masses." 3.2 solar masses
Asimov, Isaac. Guide to Earth and Space. New York: Fawcett Crest, 1991: 228. "Such a neutron star was less than 3.2 solar masses." 3.2 solar masses

Stars are objects that shine because they give off energy by process of nuclear fusion. However, there are several groups of stars that don't undergo the fusion process. Among these are the neutron stars.

The formation of neutron stars is a long process. A star more massive than the sun, must first collapse. This occurs because of an extreme downward pull of gravity. After this occurs, protons combine with electrons (they're squeezed together by gravity in the core of the star) and neutrons are formed. However, the gravitational pull is still present, thus a core of tightly compressed neutrons exists. Soon the gravitational pull becomes so strong that an explosion occurs. This is known as a supernova. Outer layers are thrown into space and a spinning core remains. This is the neutron star.

Though scientists have many different opinions of the mass of this star, the range appears to be no less than 1.4 solar masses, and no more than 3.2 solar masses. Most reported findings fall within this range. After a star excceds this upper limit, it becomes too heavy and forms a black hole. In addition, below the lower limit, the star is too small and is simply a white dwarf.

Surprisingly, though there mass is so large, the diameter of neutron stars is typically inly 10-20 kilometers (the length of Manhattan). In addition, neutron stars have magnetic fields which are billions of times stronger than the most powerful magnets on Earth. It's possible, therefore, through a field of electrons and protons, for a neutron star to emit radiation. If such a star is spinning, it is called a pulsar.

Danny Goldner -- 1997

Bibliographic Entry Result
(w/surrounding text)
Bildstein, Lars & Strohmayer, Tod. "New Views of Neutron Stars." Physics Today. vol. 52, no. 2 (February 1999): 40. "neutron stars are the extremely dense endpoints of stars that initially had a mass of more than about 8-10 [solar masses]" 8–10 solar masses
"leaving behind a remnant -- a neutron star -- packing a typical mass of 1.4 [solar masses]" 1.4 solar masses

Although neutron stars range from 1.4 to 3.2 solar masses, the mass of their parent stars are much higher. Neutron stars are formed from the supernova remains of stars with a mass between 8 and 10 times that of the sun.

Editor's Supplement -- 1999