What is the Sun's Corona ?
Images Credits : NASA/ Aubrey Gemignani
Our Sun is surrounded by a jacket of gases called an atmosphere . The Sun's corona is the utermost part of the Sun's atmosphere . The corona is usually hidden by the bright light of the Sun's surface . That makes it difficult to see without usuing special instruments . However , the corona can be viewed during a total eclipse.
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During a total solar eclipse ,the moon passes between Earth and the Sun . When this happens , the moon blocks out the bright light of the Sun . The glowing white corona can then be seen surrounding the eclipsed Sun .
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Why is the corona so dim and so hot ?
The corona reaches extremely high temperatures. However, the corona is very dim. This is because the corona is about 10 million times less dense than the Sun’s surface. This kind of low density makes the corona much less bright than the surface of the Sun. Despite this fact , high temperature of the corona stll become a mystery.
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Astronomers have been trying to solve this mystery for a long time. The corona is in the outer layer of the Sun’s atmosphere and its far from its surface. Yet the corona is hundreds of times hotter than the Sun’s surface.
Furthermore, there's NASA's mission called IRIS and it may have provided one possible answer. The purpose of the mission is to discovered packets of very hot material called "heat bombs" that travel from the Sun into the corona. In the corona, the heat bombs explode and release their energy as heat. But the astronomers think that this is one of the way to get the corona heated.
Images Credits : spaceplace.nasa.gov
Coronal Loops and Streamers
Coronal Loops. Image Credit : NASA / TRACE
The surface of the Sun is covered in magnetic fields. This is the force that makes magnets stick to metal , like the door of your refrigerator
The Sun's magnetic fields affect charged particles in the corona to form beautiful features . These include streamers, loops, and plumes. We can view these features in detail with special telescopes
Conceptual animation (not to scale) showing the Sun's Corona and Solar Wind.
Image credit : NASA's Goddard Space Flight Center / Lisa Poje
How does the corona cause solar winds ?
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The corona extends far out into the space. It comes the solar wind that travels through our solar system. The temperature of the corona's causes its particles to move at very high speeds. When the speeds are so high , the particles can escape from the Sun's gravity .