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The New Zealand Railways Magazine, Volume 13, Issue 5 (August 1, 1938)

The Sun

The Sun.

We can, therefore, picture other stars most easily by comparing or contrasting them with the particular star that we know most about, our own Sun. The habitability of the earth is due entirely to the small fraction (about one 2230 millionth) of the solar energy that reaches its surface.

The Sun has a diameter more than 109 times that of the earth, and therefore, a volume 1,300,000 times as great. Although its average density is little more than a quarter of the earth's, its mass is equal to that of 333,434 worlds like ours. From the highest levels to the deepest regions observable in its atmosphere, the absolute temperature ranges from 5,000 to 7,000 degrees Centigrade. The latter is about double the temperature of the electric arc. The greater part of the interior is believed to be above a million, whilst the central regions have the inconceivable temperature of 30 million degrees Centigrade. Although the pressure at its centre must be a million tons to the square centimetre, the sun is believed to be gaseous throughout. The terrific encounters at such a pressure and temperature must denude the atoms of most of their outer electrons. The sun is 5,000 times brighter than liquid steel, and each square yard of its surface is continually pouring out radiant energy equivalent to 70,000 horse power. Its great gravitational attraction keeps all the planets in their orbits.