The Physics Factbook

Edited by Glenn Elert -- Written by his students

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Bibliographic Entry | Result (w/surrounding text) |
Standardized Result |
---|---|---|

Namowitz, Samuel N. Heath Earth Science. Canada: Heath, 1994: 379. |
"… Sun's density is 1.4 times that of water." | 1.4 g/cm^{3} |

McGraw-Hill Encyclopedia of Science and Technology. New York: McGraw Hill, 1997: 635. |
"mean density = 1.410 g/cm^{3}" |
1.410 g/cm^{3} |

Sims, Lesley. Stars and the Sun. 1995: 55. |
"diameter = 1,392,000 km mass = 2 × 10 ^{27} tons" |
1.4 g/cm^{3} |

Hamilton, Calvin. Views of the Solar System. 1997. |
"density (g/cm^{3}) 1.140" |
1.410 g/cm^{3} |

The Sun is an average star. But different sources have different values for
the density of Sun. They are all about 1.4 g/cm^{3} or about 1.4 times
that of water.

For the third entry in the table above, I calculated the density of the Sun using the formula

ρ = *m*/*V* (density is mass
per volume)

The mass of Sun is approximately 333,000 times of Earth and the volume of the
Sun could hold more than one million Earths. The mass of the Sun is 2 × 10^{27} tons
which is 2 × 10^{33} g (one metric ton is one thousand kilograms
or one million grams). And to find the volume of the Sun I used the formula for
volume of a sphere

4/3*π*r^{3}

The Sun's diameter is 1,392,000 km or 1.392 × 10^{11} cm so its radius
is half of that: 6.96 × 10^{10} cm. Thus the volume equals

4/3*3.14*(6.96 × 10^{10} cm)^{3} = 1.41 × 10^{33} cm^{3}

and the density equals

2 × 10^{33} g/1.41 × 10^{33} cm^{3} = 1.4 g/cm^{3}

The Sun has many layers including the core, the radioactive layer, the convection layer, and the photosphere. The core is made up of hydrogen, which fuses, into helium. It is about 450,000 km in diameter. The radioactive layer is about 278,000 km deep, the convection layer is about 200,000 km deep, and the photosphere which is the Sun's surface is about 400 km deep. The density of each layer is different and thus the value calculated is merely an average value for the density of the Sun.

May Ko -- 1999

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