Wikijunior: Lo Sistèma Solar/Lo Solelh

Lo Solelh es lo centre de nòstre sistèma: lo Sistèma Solar. A mai nos semble plan importanta, es pas qu'una estela ordinària, de talha mejana que nasquèt coma d'autras fa qualques milierats de milions d'annadas. A l'entorn d'aqueste astre gravitan las 9 planetas conegudas que forman lo Sistèma Solar.

De qu'es lo Solelh?

L'estela coneguda coma Solelh es compausada essencialament de gases, mai que mai d'idrogèn mas tanben d'un autre gas que se sona èli e tanben d'autres elements quimics. Es doncas un glòb de gases intensament caud. Fa 1.391.785.000 km de diamètre, es a dire qu'es mai grand d'un milion de còps que la planeta Tèrra.

Sa lutz e calor provenon d'un procès atomic que se sona fusion nucleara: quatre bits d'idrogèn se jonhon a 4 bits d'èli; lo Solelh gives off calor e lutz, e pèrd de material solid dins l'espaci. Tot aquò all happens cada segonda e lo Solelh pèrd 4 milions de tonas de matèria durant aquel periòde brèu. Lo centre del Solelh a una temperatura de 15 milions de gras centigrads, cooling a 6 mila gras at sa susfàcia gasosa.

Se deu pas creire que nòstre Solelh es immobil dins l'espaci; en realitat, possedís doas menas de movement. Lo primièr es aparentament un movement en linha dirècta dins la direccion de la constellacion Hercules a la velocitat d'aperaquí 12 km per segonda. Pasmens vist que lo Solelh es part del sistèma de la Via Lactèa, e since our Milky Way galaxy rotates lentament a l'entorn de son quite centre, lo Solelh se mòu tanben a la velocitat de 175 km per segonda as part del sistèma rotating Milky Way.

Aquesta fotografia del Solelh, presa pel Telescòpi Optic Solar d'Hinode lo 12 de genièr de 2007, revèla la natura filamentosa de plasma connecting regions de polaritat magnetica diferenta.

Our Sun es una estela in 100.000 milions, which goes to make up our galaxia, la Via Milky. Some estelas son menudas e dim while d'autres son de super-giants en comparason. Our Milky Way is shaped de dos uòus fregits back to back and is a noticeable spiral formacion d'estelas. In terms de talha, aquesta galaxia nòstra es enòrma, at the speed de light de 300.000 km a second it takes 4,2 ans to travel a la Tèrra a partir de our nearest estela - Proxima Centauri. On aquesta escala it takes a single pulse de lum 100.000 annadas per poder traversar la longor de nòstra galaxia d'un cap a l'autre.

Dont mai lo Solelh ven vièlh, dont mai gradualament expands e cools; although; prior to aquel periòde, lo Solelh will "burn" èli o other e mai d'elements mai pesucs as the core del Solelh reaches de temperaturas e de densitats mai e mai importantas. As a result of the Sun's increased temperature life on Earth will cease. The extreme calor generada serà aital catastrofica per la Tèrra: los oceans will boil away e la vida coma la coneissèm uèi s'acabarà. Long before lo Solelh reaches the Red Giant fasa, la susfàcia de la Tèrra will literally be molten as la temperatura del Solelh aumenta. It is estimated que the brilliancy del Solelh will increase by 10% over the next 1.1 billion years or more, and in about 6.5 billion annadas, our aging star will have doblat sa luminositat actuala.

Eight billion years from now, quand lo Solelh does reach la fasa de Red Giant, the Sun's radius s'estendrà plan enlà de l'orbita actuala de Vènus, e deuriá causar la destruccion totala de la Tèrra.

Our own Solelh will continue de shine per las generacions venidoiras, fins que sa supply d'idrogèn fuel is used up, e alara sas regions centralas mermarà as different fusion reactions compensate. Lo Solelh puèi will then expand into a huge red-giant star eating up totas las planetas de Mercuri a Mart (Tèrra compresa), e vaporising las atmosfèras de las planetas gasosas the remaining gas giant fins qu'aquelas tanben seràn destroyed. Fortunately by this time our human race will have became technically advanced, so we will have set off on journeys to find safe havens on other planets among las estelas - coma o fan dins Star Trek.

The sun’s brilliant surface layer se sona la fotosfèra (çò es l'‘esfèra de lutz’). Una observacion incorrècta del Solelh causes blindness because of the tremendous amount de la lutz visibla e invisibla coming off de sas surface.

Sunspots are appropriately named. They appear coma de tacas sul disc del Solelh. A sunspot will have una region centrala plan fosca qu'es coneguda coma the umbra. Es sovent surrounded by a less dark halo known coma la penumbra.

The umbra es fosca ja qu'es mai cooler (aperaquí 3.500°C) que the surrounding sunscape (around 5.500°C). They appear move across the Solelh as the Solelh spins on its axis. Because lo Solelh is gaseous in nature e se compòrta coma un fluid it does not spin coma un còs rigid. A spot near the equator will take about 25 jorns per complete una rotacion. A spot near a pole, if there were ever one there, will take over a mes to make the trip. Collections of sunspot sketches over a periòde de several years reveal the 11-year cycle of sunspots. Over that periòde los nombres of spots goes from a maximum to a minimum and back.

There also appears to be a relationship with the talha e lo nombre of sunspots e lo temps de la Tèrra. During the Maunder minimum 1645-1715 there were no observable sunspots and Britain plunged into a mini ice age. However in resent years 2003 – 2004 there have been large sunspot numbers with some unusually large sunspots. This has coincided amb d'estius plan cauds e is believed to be one of the causes for global warming.

A mai de calor e lutz, lo Solelh tanben genera de vents solars, a stream de particulas ionizadas que radiates outward through lo sistèma solar a de velocitats bèlas. Un dels efièches del vent solar es que fòrça las coas de las cometas a point away del Solelh.

The solar wind also interacts amb lo camp magnetic terrèstre, causing the aurora e d'autres fenomèns. Solar flares — erupcions — de gas idrogèn sus the surface del Solelh pòt tanben causar de disturbances dins lo camp magnetic de la Tèrra.

La cromosfèra se tròba ensús de la fotosfèra. L'energia solara passa a travèrs aquela region on its way out del centre del Solelh.

Faculae and flares arise dins la cromosfèra. Faculae are bright luminous d'idrogèn clouds, which form above regions where sunspots son a mand de se formar. Flares are bright filaments of hot gas emerging from sunspot regions.

Sunspots are dark depressions on the fotosfèra with a typical temperatura de 4.000°C. En 1998, los scientifics observèron for primièr còp las solar flares producing seismic waves dins l'interior del Solelh que resemble las que crean los tèrratrems. They observed a flare-generated solar quake equivalent to an 11.3 magnitude earthquake. It contained about 40,000 times the energy released in the great 1906 San Francisco earthquake.

The corona is the outer part of the Sun's atmosphere. It is in this region that prominences appear. Prominences are immense clouds of glowing gas that erupt from the upper chromosphere. The outer region of the corona stretches far into space and consists of particles travelling slowly away from the Sun. The corona can only be seen during total solar eclipses.

Eclipses occur when the Sun, Earth and Moon line up. They are rare because the Moon usually passes above or below the imaginary line connecting Earth and the Sun. In a solar eclipse the Moon passes directly in front of the Sun. This can only happen when the phase of the Moon is "new." That occurs because for Earth-based observers, the far side of the Moon is illuminated while the side facing Earth is in darkness. The Moon like any sphere, casts a shadow. A solar eclipse occurs when that shadow sweeps across Earth. The black cone is called the umbra. An observer anywhere inside that region is completely in shade. None of the Sun is visible from there.

Surrounding the umbra is the penumbra. An observer there will see some, but not all, of the Sun. Outside of these regions all of the Sun is visible. Note that the tip of the umbra barely touches Earth. At the current time the position of the Moon relative to the Sun is such that the Moon, which is 400 times smaller that the Sun, is 400 times closer! This means that the two objects appear to be the same size in the sky. Only observers at the tip of the umbral cone will see a total solar eclipse. A large number of observers across the globe will see a partial solar eclipse if they are in the penumbra.

An annular eclipse is a special partial solar eclipse. Because the Moon's orbit around Earth is an ellipse, not a circle, the Moon's distance from Earth varies. When the Moon is far from Earth it appears slightly smaller in the sky. (Earth's orbit around the Sun is also an ellipse, and during January, Earth is at its closest point to the Sun. The Sun's size is slightly larger than during the rest of the year.) With a "small" Moon and a "large" Sun the Moon will not completely block out the Sun. The umbra does not touch Earth. An observer would have to be above the surface of Earth to see a total eclipse. For individuals in just the right location, the Sun appears as a ring (annulus) around the silhouetted Moon.

In a lunar eclipse the Moon moves into Earth's shadow. They can only occur when the moon is "full." Observers on the night side of Earth see the Moon take on a reddish hue as it moves into Earth's umbra. If the entire disk of the Moon moves into the umbra it is a total lunar eclipse. If only a portion does, then it is a partial lunar eclipse.

Penumbral lunar eclipses are very difficult to detect because the Moon dims only slightly while moving through that region. Lunar eclipses are more common than solar eclipses. Total eclipses of the Sun and Moon are partial before and after totality.

Moving away from the sun at the centre of our solar system we arrive at the closest planet, Mercury, while there are eight known planets altogether including Earth. A planet is a sizeable body that orbits around a star. A planet also has no light of its own and therefore is only visible by reflecting starlight, in our case sunlight off its surface.