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Observing the Sun Through History

Stonehenge and Eclipse
For much of history, humans have studied the sky and the Sun. Ancient people built structures like Stonehenge to observe the Sun's passage through the seasons.

The advent of the telescope in the 1600s allowed astronomers such as Christopher Scheiner and Galileo Galilei to observe and sketch sunspots. Solar flares were discovered in 1859 when Richard Carrington focused his telescope on the Sun and saw a bright flash on the projected image.

Skylab Prominence
Further study required escaping Earth's atmosphere, which distorts and limits our view of the Sun and other celestial objects. By launching telescopes and instruments into space, scientists can see the Sun in a whole new light.
From Stonehenge to Satellites
The Changing Sun
Like Earth, the Sun has seasons. More precisely, it has a cycle that lasts about 11 years. In this sequence of images of X rays from the Sun's corona, notice how the corona changes from solar maximum (left side) to solar minimum (right side). The bright areas are called active regions, where intense magnetic fields trap hot plasma.

The number of sunspots rises and falls in about 11 years, called the sunspot cycle. A period marked by many sunspots is known as solar maximum, while a quiet period with few sunspots is called solar minimum. As the number of sunspots increases, so do the frequency and intensity of active regions and solar storms. Scientists predicted that solar cycle 23 should peak in 2000-2001.
Seeing the Invisible

Yohkoh Soft X-Ray

To unlock the Sun's secrets, scientists must find ways to see what is invisible to the human eye. The Sun radiates energy in wavelengths, most of which are outside the visible spectrum. For example, the Sun's photosphere produces most of the light we see, while its corona produces X-rays that can only be seen with special instruments. Each type of radiation carries different information about the Sun's chemistry and magnetic field.
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Next: Earth -- In the Path of the Storm
Back: Our Dynamic Sun
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Last Modified: 1/20/2000 TMV

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