Query: Solar Cycle Length proves its the sun.

Relevant passages:
Sun <=SEP=> The Sun is the star at the center of the Solar System . It is a nearly perfect sphere of hot plasma , with internal convective motion that generates a magnetic field via a dynamo process . It is by far the most important source of energy for life on Earth . Its diameter is about 109 times that of Earth , and its mass is about 330,000 times that of Earth , accounting for about 99.86 % of the total mass of the Solar System .  About three quarters of the Sun 's mass consists of hydrogen ( ~ 73 % ) ; the rest is mostly helium ( ~ 25 % ) , with much smaller quantities of heavier elements , including oxygen , carbon , neon , and iron .   The Sun is a G-type main-sequence star ( G2V ) based on its spectral class . As such , it is informally referred to as a yellow dwarf . It formed approximately 4.6 billionAll numbers in this article are short scale . One billion is 109 , or 1,000,000,000 . years ago from the gravitational collapse of matter within a region of a large molecular cloud . Most of this matter gathered in the center , whereas the rest flattened into an orbiting disk that became the Solar System . The central mass became so hot and dense that it eventually initiated nuclear fusion in its core . It is thought that almost all stars form by this process .   The Sun is roughly middle-aged ; it has not changed dramatically for more than four billion years , and will remain fairly stable for more than another five billion years . After hydrogen fusion in its core has diminished to the point at which it is no longer in hydrostatic equilibrium , the core of the Sun will experience a marked increase in density and temperature while its outer layers expand to eventually become a red giant . It is calculated that the Sun will become sufficiently large to engulf the current orbits of Mercury and Venus , and render Earth uninhabitable .   The enormous effect of the Sun on Earth has been recognized since prehistoric times , and the Sun has been regarded by some cultures as a deity . The synodic rotation of Earth and its orbit around the Sun are the basis of the solar calendar , which is the predominant calendar in use today .

Axial precession <=SEP=> In astronomy , axial precession is a gravity-induced , slow , and continuous change in the orientation of an astronomical body 's rotational axis . In particular , it can refer to the gradual shift in the orientation of Earth 's axis of rotation , which , similar to a wobbling top , traces out a pair of cones joined at their apices in a cycle of approximately 26,000 years . The term `` precession '' typically refers only to this largest part of the motion ; other changes in the alignment of Earth 's axis -- nutation and polar motion -- are much smaller in magnitude .   Earth 's precession was historically called the precession of the equinoxes , because the equinoxes moved westward along the ecliptic relative to the fixed stars , opposite to the yearly motion of the Sun along the ecliptic . This term is still used in non-technical discussions , that is , when detailed mathematics are absent . Historically ,  the discovery of the precession of the equinoxes is usually attributed in the west to the Hellenistic-era ( 2nd century BC ) astronomer , Hipparchus , although there are claims of its earlier discovery , such as in the Indian text , Vedanga Jyotisha , dating from 700 BC .  With improvements in the ability to calculate the gravitational force between and among planets during the first half of the nineteenth century , it was recognized that the ecliptic itself moved slightly , which was named planetary precession , as early as 1863 , while the dominant component was named lunisolar precession . Their combination was named general precession , instead of precession of the equinoxes .   Lunisolar precession is caused by the gravitational forces of the Moon and Sun on Earth 's equatorial bulge , causing Earth 's axis to move with respect to inertial space . Planetary precession ( an advance ) is due to the small angle between the gravitational force of the other planets on Earth and its orbital plane ( the ecliptic ) , causing the plane of the ecliptic to shift slightly relative to inertial space . Lunisolar precession is about 500 times greater than planetary precession . In addition to the Moon and Sun , the other planets also cause a small movement of Earth 's axis in inertial space , making the contrast in the terms lunisolar versus planetary misleading , so in 2006 the International Astronomical Union recommended that the dominant component be renamed , the precession of the equator , and the minor component be renamed , precession of the ecliptic , but their combination is still named general precession . Many references to the old terms exist in publications predating the change .

Solar eclipse of August 21, 2017 <=SEP=> A total solar eclipse will take place on Monday , August 21 , 2017 . A solar eclipse occurs when the Moon passes between Earth and the Sun , thereby totally or partly obscuring the image of the Sun for a viewer on Earth . A total solar eclipse occurs when the Moon 's apparent diameter is larger than the Sun 's , blocking all direct sunlight , turning day into darkness . Totality occurs in a narrow path across Earth 's surface , with the partial solar eclipse visible over a surrounding region thousands of kilometers wide .   This eclipse is the 22nd of the 77 members of Saros series 145 , the one that also produced the solar eclipse of August 11 , 1999 . Members of this series are increasing in duration . The longest eclipse in this series will occur on June 25 , 2522 and last for 7 minutes and 12 seconds .