The Milky Way and other galaxies

This Milky Way Galaxy 200 billion stars page and the entire website are excerpted from You and the Universe, a handmade, individualized fine art book on astrology, mythology and astronomy through which the recipient's complete astrological reading is woven.

Our Sun is a star 864,000 miles in diameter, composed of 75% hydrogen and 25% helium, the two lightest elements in the universe. It contains 99.8% of all of the mass in the solar system—the planets and everything else amount to only 1/500th of the total. The surface of the Sun is 5,800° on the absolute Kelvin scale (or 9600° Fahrenheit), but in the corona—which extends out for millions of miles, is ten billion times less dense than the atmosphere of the Earth at sea level, and is only visible during eclipses—the temperature averages over one million degrees Kelvin (2 million Fahrenheit). In fact in some places the corona can reach 3 million degrees Kelvin (5 million Fahrenheit)! Since temperatures ordinarily fall as one moves away from the source of the heat, the source of the corona's relatively high temperature remains an unsolved puzzle. At the Sun’s core the temperature is 15.6 million degrees, the pressure is 250 billion times the pressure at sea level on Earth, and the density of this lightest of all gases is more than 150 times that of water. To read more about our Sun, the star called Sol, click here.

The Sun is an average yellow star in a spiral of about 200 billion stars, planets and clouds of interstellar gas known collectively as the Milky Way. An infrared photo of the Milky Way is shown above. Half way from its center to its outer edge, the Sun takes a quarter of a billion years to revolve once around it. If all of the stars in our galaxy were each a grain of sand, they would cover an entire football field to a depth of half an inch. Yet every one of those grains of sand contains 20 million times as many molecules as there are stars in the entire Milky Way galaxy!