Four Trillion Trillion Light Bulbs

Next time you are screwing in a light bulb, notice its wattage. A watt is a measure of power, or how much energy is produced or consumed each second. A 100 watt bulb uses 100 joules of energy every second. For comparison, the sun produces 4 x 1026 watts of power. That's a lot of light bulbs—four trillion trillion of them, to be exact. This rate of energy production is called the sun's luminosity. Many stars have luminosities much higher than that of the sun.

The source of the sun's power—and that of all stars, during most of their lifetimes— is the fusing together of nuclei. Stars first convert hydrogen into helium, and heavier elements come later (we discuss this process in Chapter 19, "Black Holes: One-Way Tickets to Eternity"). The only fusion reactions that we have been able to produce on the earth are uncontrolled reactions known as hydrogen bombs. The destructive force of these explosions gives insight into the enormous energies released in the core of the sun. Nuclear fusion could be used as a nearly limitless supply of energy on the earth; however, we are not yet able to create the necessary conditions on Earth for controlled fusion reactions.

The solar surface as seen with the Solar and Heliospheric Observatory (SOHO), an international solar observatory jointly operated by the European Space Agency and NASA. This image shows an impressive array of sunspots visible on March 29, 2001.

(Image from NASA/ESA)

Telescopes Mastery

Telescopes Mastery

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