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Individual sunspots or groups of sunspots may last anywhere from a few days to a few months, but eventually decay. Sunspots expand and contract as they move across the surface of the Sun, with diameters ranging from 16 km (10 mi) [3] to 160,000 km (100,000 mi). [4] Larger sunspots can be visible from Earth without the aid of a telescope. [5]
Sunspots are relatively dark areas on the Sun's radiating 'surface' (photosphere) where intense magnetic activity inhibits convection and cools the Photosphere. Faculae are slightly brighter areas that form around sunspot groups as the flow of energy to the photosphere is re-established and both the normal flow and the sunspot-blocked energy ...
Sunspots result from the blockage of convective heat transport by intense magnetic fields. Sunspots are cooler than the rest of the photosphere, with effective temperatures of about 4,000°C (about 7,000°F). Sunspot occurrence follows an approximately 11-year period known as the solar cycle, discovered by Heinrich Schwabe in the 19th century.
The dark spectra lines in the spectrum of the emitted light split into three components and the strength of the circular polarisation in parts of the spectrum increases significantly. This polarisation effect is a powerful tool for astronomers to detect and measure stellar magnetic fields.
The magnetic flux pushes the hotter photosphere aside, exposing the cooler plasma below, thus creating the relatively dark sun spots. High-resolution X-ray images of the Sun's corona photographed by Skylab in 1973, by Yohkoh in 1991–2001, and by subsequent space-based instruments revealed the structure of the corona to be quite varied and ...
There are records of observing sunspots from 28 BC, but that is the first known drawing of sunspots, almost 500 years before the telescope. His drawing seems to come around solar maximum. Five days later, the Korean astronomer saw the northern lights above his country, so this is also the first prediction of coronal mass ejection .
These have also been used on century times scales but, in addition, instrumental data are increasingly available (mainly telescopic observations of sunspots and thermometer measurements of air temperature) and show that, for example, the temperature fluctuations do not match the solar activity variations and that the commonly-invoked ...
The Star-Spectroscope of the Lick Observatory in 1898. Designed by James Keeler and constructed by John Brashear.. Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, including visible light, ultraviolet, X-ray, infrared and radio waves that radiate from stars and other celestial objects.