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List of solar cycles. Solar cycles are nearly periodic 11-year changes in the Sun 's activity that are based on the number of sunspots present on the Sun's surface. The first solar cycle conventionally is said to have started in 1755. The source data are the revised International Sunspot Numbers (ISN v2.0), as available at SILSO. [1]
Sun. The Sun is the star at the center of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light and infrared radiation with 10% at ultraviolet energies.
The Suess cycle, or de Vries cycle, is a cycle present in radiocarbon proxies of solar activity with a period of about 210 years. It was named after Hans Eduard Suess and Hessel de Vries . [ 48 ] Despite calculated radioisotope production rates being well correlated with the 400-year sunspot record, there is little evidence of the Suess cycle ...
Sun has fused all of the hydrogen in the core and starts to burn hydrogen in a shell surrounding its core, thus ending its main sequence life. Sun begins to ascend the red-giant branch of the Hertzsprung–Russell diagram, growing dramatically more luminous (by a factor of up to 2,700), larger (by a factor of up to 250 in radius), and cooler ...
Since 1978, solar irradiance has been directly measured by satellites with very good accuracy. [11]: 6 These measurements indicate that the Sun's total solar irradiance fluctuates by +-0.1% over the ~11 years of the solar cycle, but that its average value has been stable since the measurements started in 1978.
The proton–proton chain, also commonly referred to as the p–p chain, is one of two known sets of nuclear fusion reactions by which stars convert hydrogen to helium. It dominates in stars with masses less than or equal to that of the Sun, [2] whereas the CNO cycle, the other known reaction, is suggested by theoretical models to dominate in ...
The main sequence is visible as a prominent diagonal band from upper left to lower right. This plot shows 22,000 stars from the Hipparcos Catalog together with 1,000 low-luminosity stars (red and white dwarfs) from the Gliese Catalogue of Nearby Stars. In astronomy, the main sequence is a classification of stars which appear on plots of stellar ...
720,000 km/h (450,000 mi/h) [10] Orbital period. ~230 million years [10] The Solar System[d] is the gravitationally bound system of the Sun and the objects that orbit it. [11] It was formed about 4.6 billion years ago when a dense region of a molecular cloud collapsed, forming the Sun and a protoplanetary disc.