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In solar physics, a spicule, also known as a fibril or mottle, [a] is a dynamic jet of plasma in the Sun's chromosphere about 300 km in diameter. [1] They move upwards with speeds between 15 and 110 km/s from the photosphere and last a few minutes each [ 1 ] before falling back to the solar atmosphere. [ 2 ]
Earth orbits the Sun at an average distance of 149.60 million km (92.96 million mi), or 8.317 light-minutes, [1] in a counterclockwise direction as viewed from above the Northern Hemisphere. One complete orbit takes 365.256 days (1 sidereal year), during which time Earth has traveled 940 million km (584 million mi). [2]
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.
Earth rotates once in about 24 hours with respect to the Sun, but once every 23 hours, 56 minutes and 4 seconds with respect to other distant stars . Earth's rotation is slowing slightly with time; thus, a day was shorter in the past. This is due to the tidal effects the Moon has on Earth's rotation.
Animation showing equation of time and analemma path over one year.. The United States Naval Observatory states "the Equation of Time is the difference apparent solar time minus mean solar time", i.e. if the sun is ahead of the clock the sign is positive, and if the clock is ahead of the sun the sign is negative.
In that early age, a moderate greenhouse effect comparable to today's would have been sufficient to explain a largely ice-free Earth. Evidence for a more active early Sun has been found in meteorites. [25] The temperature minimum around 2.4 Ga goes along with a cosmic ray flux modulation by a variable star formation rate in the Milky Way. The ...
In roughly 5 billion years, the Sun will cool and expand outward to many times its current diameter (becoming a red giant), before casting off its outer layers as a planetary nebula and leaving behind a stellar remnant known as a white dwarf. In the distant future, the gravity of passing stars will gradually reduce the Sun's retinue of planets.
The sine of a 30° angle is 1/2, whereas the sine of a 90° angle is 1. Therefore, the angled sunbeam spreads the light over twice the area. Consequently, half as much light falls on each square mile. This projection effect is the main reason why Earth's polar regions are much colder than equatorial regions. On an annual average, the poles ...