Photos of the Sun

Solar corona. The Sun and the giant planets

Solar corona. The Sun and the giant planets

Covering the photosphere or visible surface of the Sun, the weak and faint solar corona is not easily seen from Earth, but the measurements confirm that it is hundreds of times hotter than the photosphere itself.

What causes the solar corona to be so hot? Astronomers have long sought the source of that heat in the magnetic fields that launch monstrous loops of solar plasma over the photosphere. However, new deeply detailed observations of the crown loops made in orbit by the TRACE satellite bring us closer to that undiscovered energy source.

This and other images of the TRACE, taken at the end of the ultraviolet, show that most of the warming comes from the lower part of the crown, near the bases of the loops that arise from the solar surface and return to it. The new results cast doubt on the usual theory, which is based on uniform heating of the loops. This impressive image of the TRACE shows groups of these majestic hot loops, which can expand more than 30 times the diameter of the planet Earth.

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