Query: The lack of any sunspots suggests the current solar minimum is one of the 'deepest' in 100 years.

Relevant passages:
Maunder Minimum <=SEP=> The Maunder Minimum , also known as the `` prolonged sunspot minimum '' , is the name used for the period starting in about 1645 and continuing to about 1715 when sunspots became exceedingly rare , as noted by solar observers of the time .   The term was introduced after John A. Eddy published a landmark 1976 paper in Science . Astronomers before Eddy had also named the period after the solar astronomers Annie Russell Maunder ( 1868 -- 1947 ) and E. Walter Maunder ( 1851 -- 1928 ) , who studied how sunspot latitudes changed with time . The period which the husband and wife team examined included the second half of the 17th century .   Two papers were published in Edward Maunder 's name in 1890 and 1894 , and he cited earlier papers written by Gustav Spörer . Because Annie Maunder had not received a university degree ( due to restrictions at the time ) , her contribution was not publicly recognized .   Spörer noted that , during a 28-year period ( 1672 -- 1699 ) within the Maunder Minimum , observations revealed fewer than 50 sunspots . This contrasts with the typical 40,000 -- 50,000 sunspots seen in modern times .   Like the Dalton Minimum and Spörer Minimum , the Maunder Minimum coincided with a period of lower-than-average European temperatures .

Coronal cloud <=SEP=> A coronal cloud is the cloud of hot plasma gas surrounding a coronal mass ejection . It is usually made up of protons and electrons . When a coronal mass ejection occurs , it is the coronal cloud that usually reaches Earth and causes damage to electrical equipment and space satellites , not the ejection or flare itself . The damage is mostly the result of the high amount of electricity moving through the atmosphere .   A coronal cloud is released when a solar flare becomes a coronal mass ejection ; the coronal cloud often contains more radioactive particles than the mass ejection itself . A coronal mass ejection occurs when a solar flare becomes so hot that it snaps and breaks in two , becoming a `` rope '' of heat and magnetism that stretches between two sunspots . The resulting coronal mass ejection can be compared to a horseshoe magnet , the sunspots being the poles and the oscillating magnetic connector the handle . Coronal mass ejections typically do not last very long , because they cool down as the coronal cloud of gas is released and begins to hurtle away from the sun .

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 .