Temperature of the sun
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Sun’s Surface Temperature: Photosphere and Effective Temperature
The surface of the Sun, known as the photosphere, has an effective temperature of about 5777 K to 5800 K (approximately 5500°C) 3710. This temperature is determined by the energy radiated from the Sun and is consistent with the Sun behaving like an ideal thermal radiator, or blackbody, whose emission peaks in the visible spectrum 710. The photosphere is a thin layer, only about 100 km thick, from which most of the Sun’s light escapes into space .
Solar Core and Fusion Reactions
The Sun’s energy comes from nuclear fusion reactions in its core, where hydrogen atoms combine to form helium, releasing vast amounts of energy. While the core temperature is much higher than the surface, reaching millions of degrees Kelvin, the temperature at the photosphere is what we observe directly from Earth .
Solar Atmosphere: Corona and Temperature Mystery
Above the photosphere, the Sun’s atmosphere includes the corona, which is much hotter than the surface, reaching temperatures of up to a million degrees Kelvin. This is a long-standing mystery in solar physics, as the outer atmosphere is much hotter than the visible surface. Recent research suggests that magnetic waves driven by turbulence beneath the surface may help heat the corona to these extreme temperatures 510.
Historical Estimates and Measurement Challenges
Early attempts to estimate the Sun’s temperature, such as those by Newton and later by 19th-century scientists, produced a wide range of values, often much higher than modern measurements. For example, some early calculations suggested temperatures of several million degrees, but these were based on indirect reasoning and have since been revised with better understanding and technology 1268. Modern measurements, using both ground-based and spaceborne instruments, have confirmed the photosphere’s temperature to be around 5777 K 3710.
Variations and Solar Cycle Effects
There are small variations in the Sun’s surface temperature related to solar activity cycles. These changes can affect the total solar irradiance received by Earth, but the average temperature of the photosphere remains close to 5777 K .
Conclusion
In summary, the temperature of the Sun’s visible surface, or photosphere, is about 5777 K (5500°C), while the outer atmosphere (corona) can reach up to a million degrees Kelvin. The Sun’s core, where fusion occurs, is even hotter, but the temperature we observe from Earth is that of the photosphere. This understanding is based on modern astrophysical measurements and models, which have resolved many of the uncertainties present in early scientific estimates 357910.
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