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It is most easily seen during a total solar eclipse. This is the Sun’s outer atmosphere and extends to millions of kilometres into outer space. While the convection zone and partly also the solar photosphere are dominated by flows which are capable of moving regions of strong magnetic flux around, the transition region and corona are dominated by the magnetic field which forces the plasma to move predominantly along field lines. Across the transition zone, the temperature of the solar plasma soars to nearly a million degrees Celsius. This is a thin, irregular layer that separates the relatively cool chromosphere from the much hotter corona. Spires of chromospheric gas, known as spicules, can reach up to a height of 10 0000 km. In general, the chromosphere is roughly 1000–2000 kilometres thick, with a temperature that rises from around 4000 to about 25 000 degrees Celsius. This is the layer above the photosphere, where the density of plasma drops dramatically. The temperature of the photosphere varies from place to place but lies between 45 degrees Celsius. It is where the energy generated in the core can finally move freely through space. Almost all radiation from the Sun is emitted from this thin layer of several 100 km thickness, which lies at the upper boundary of the convection zone. This is the visible ‘surface’ of the Sun. This makes it buoyant and so it rises rapidly, creating a turbulent convection pattern, rather like a boiling pan of water – only 200 000 km deep and surrounding the entire Sun. Plasma at the base of the zone is heated rapidly. While the top layer is the same temperature as the photosphere (between 4500 – 6000 degrees Celsius), the base of the convective zone reaches two million degrees Celsius.
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This lies between the deeper, radiative zone and the photosphere. At the base, next to the Sun’s core, the temperature is around seven million degrees Celsius. At the top of the zone, the temperature is around two million degrees Celsius. It takes photons around 170 000 years to pass through the radiative zone: The photons travel at the speed of light, but can travel only a few millimetres at a time before they are absorbed by an atom and then re-emitted in any direction. Instead, the energy created in the core diffuses slowly through the plasma. Although not as dense as the core, the plasma is still packed so tightly in the radiative zone that convection cannot take place. Every second, the Sun converts four million tonnes of matter into energy in this way, which begins a slow journey towards the surface. This, combined with the huge pressure and density of the plasma force hydrogen nuclei to fuse together, creating helium and releasing vast quantities of energy in the process. The temperature in the core is around 15 million degrees Celsius. These speeds are so high that the particles can escape the Sun's gravity.Ĭonceptual animation (not to scale) showing the Sun's corona and solar wind.This is where the Sun generates its energy. The corona's temperature causes its particles to move at very high speeds. From it comes the solar wind that travels through our solar system. We can view these features in detail with special telescopes. These include streamers, loops, and plumes. The Sun's magnetic fields affect charged particles in the corona to form beautiful features. This is the force that makes magnets stick to metal, like the door of your refrigerator. The surface of the Sun is covered in magnetic fields. But astronomers think that this is only one of many ways in which the corona is heated. In the corona, the heat bombs explode and release their energy as heat. The mission discovered packets of very hot material called "heat bombs" that travel from the Sun into the corona. Yet the corona is hundreds of times hotter than the Sun’s surface.Ī NASA mission called IRIS may have provided one possible answer. The corona is in the outer layer of the Sun’s atmosphere-far from its surface. This is the opposite of what seems to happen on the Sun.Īstronomers have been trying to solve this mystery for a long time. But when you walk away from the fire, you feel cooler. Imagine that you’re sitting next to a campfire. The corona’s high temperatures are a bit of a mystery. Image of corona from NASA's Solar Dynamics Observatory showing features created by magnetic fields. This low density makes the corona much less bright than the surface of the Sun.
![sun corona helium sun corona helium](https://cdn.mos.cms.futurecdn.net/H3wgQVehsRLqAJmuYaN94M-1024-80.jpg)
Why? The corona is about 10 million times less dense than the Sun’s surface. The corona reaches extremely high temperatures.
#Sun corona helium how to
Find tips on how to safely view an eclipse here.
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Remember to never look directly at the Sun, even during an eclipse.