| The Solar System | |
| File:Solar System.JPG | |
| Measure of Distances | |
|---|---|
| Note that all distances are measured from the sun | |
| Astronomical Unit (AU) | 1AU = 149597870.691 kilometers |
| Parsec (pc) | 1pc = 30856775810000 kilometers |
Information about the Solar System
The Solar System consists of the Sun and those celestial objects bound to it by gravity, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. This solar system is part of Milky Way Galaxy and is positioned in the inner rim of the Galaxy's Orion Arm, in the Local Fluff inside the Local Bubble, and in the Gould Belt, at a distance of 7.62±0.32 kiloparsec (~25,000±1,000 light years) from the Galactic Core.
The solar system consists of four smaller inner planets; Mercury, Venus, Earth and Mars. These planets are called terrestrial planets and are primarily composed of rocks and metals. The four outer planets; Jupiter, Saturn, Uranus and Neptune are called gas giants and are composed largely of hydrogen and helium and are far more massive than the terrestrial planets. At the edge of the solar system is Pluto, which was once considered as a planet but now is categorized as a dwarf planet in 2006.
The Solar System is also home to two main belts of small bodies. The asteroid belt, which lies between Mars and Jupiter, is similar to the terrestrial planets as it is composed mainly of rock and metal. The Kuiper belt, which lies beyond Neptune's orbit and within Pluto's orbit and is composed mostly of ices such as water, ammonia and methane.
Sol
The Sun is the star at the center of the Solar System. The Sun is a yellow main sequence star comprising about 99.86% of the total mass of the Solar System. As the Sun exists in a plasmatic state and is not solid, it rotates faster at its equator than at its poles. The period of this actual rotation is approximately 25.6 days at the equator and 33.5 days at the poles. Gravity acts on the gases of the sun, primarily hydrogen, to generate very large temperatures and pressures at the sun's core. these conditions make nuclear fusion possible, in which, hydrogen is converted into helium and enormous quantities of energy in the form of heat, light and radiation. Using Einstein's equation and knowing how much radiation is ejected out of the sun, the present brightness of the sun can be maintained by converting just over 4 million tons of matter every second.
The planets of Sol
The inner planets. From left to right: Mercury, Venus, Earth, and Mars (sizes to scale)
Mercury
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 days. Mercury is similar in appearance to the Earth's Moon: it is heavily cratered with regions of smooth plains. However, unlike the moon, it has a large iron core, which generates a magnetic field about 1% as strong as that of the Earth. Note that Mercury's atmosphere is constantly blasted off its surface by the solar wind and therefore is incapable in supporting life unless drastically terraformed.
Venus
- Main article: Venus
Venus is close in size to Earth, and is structurally similar to Earth, it has a thick silicate mantle around an iron core, a substantial atmosphere and evidence of internal geological activity. However, it is much drier than Earth and its atmosphere is ninety times as dense. Venus has no natural satellites. It is the hottest planet, with surface temperatures over 400 °C, most likely due to the amount of greenhouse gases in the atmosphere, mainly consisting carbon dioxide and a small amount of nitrogen.
Earth
Earth is the largest and densest of the inner planets, the only one known to have current geological activity, and is the only place in the solar system where life naturally exists. Earth's atmosphere is radically different from those of the other planets, having been altered by the presence of life to contain 21% free oxygen.It has one natural satellite, the Moon, the only large satellite of a terrestrial planet in the Solar System.
Mars
- Main article: Mars
Mars is smaller than Earth and Venus. It is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the volcanoes, valleys, deserts and polar ice caps of Earth. It possesses a tenuous atmosphere of mostly carbon dioxide. Its red colour comes from iron oxide (rust) in its soil. Mars has two tiny natural satellites (Deimos and Phobos) which are small and irregularly shaped. These may be captured asteroids.
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. Jupiter is primarily composed of hydrogen with a quarter of its mass being helium; it may also have a rocky core of heavier elements. Jupiter's strong internal heat creates a number of distinct features in its atmosphere, such as cloud bands and the Great Red Spot. Jupiter has sixty-three known satellites. The four largest, Ganymede, Callisto, Io, and Europa, show similarities to the terrestrial planets, such as volcanism and internal heating.Ganymede, the largest satellite in the Solar System, is larger than Mercury.
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. The planet Saturn is composed of hydrogen, with small proportions of helium and trace elements. The interior consists of a small core of rock and ice, surrounded by a thick layer of metallic hydrogen and a gaseous outer layer. Saturn has a prominent system of rings, consisting mostly of ice particles with a smaller amount of rocky debris and dust.
Uranus
Uranus is the lightest of the outer planets. Uniquely among the planets, it orbits the Sun on its side; its axial tilt is over ninety degrees to the ecliptic. It has a much colder core than the other gas giants, and radiates very little heat into space. Uranus has twenty-seven known satellites, the largest ones being Titania, Oberon, Umbriel, Ariel and Miranda. Uranus's atmosphere, while similar to Jupiter's and Saturn's in being composed primarily of hydrogen and helium, contains a higher proportion of "ices" such as water, ammonia and methane, along with traces of hydrocarbons.
Neptune
Neptune is the eighth and outermost-known planet from the Sun in the Solar System, after Pluto was degraded from a planet to a dwarf planet. Neptune is similar in composition to Uranus, and both have compositions which differ from those of Jupiter and Saturn. The interior of Neptune, like that of Uranus, is primarily composed of ices and rock. Traces of methane in the outermost regions in part account for the planet's blue appearance. Neptune's atmosphere is notable for its active and visible weather patterns such as the Great Dark Spot.
Dwarf Planets
Pluto
- Main article: Pluto
Reclassified as a dwarf planet in 2006, Pluto is one of the most remote objects in the Solar System. It is approximately two-thirds the size of the Moon and exists in a binary system with its satellite, Charon. Pluto is primarily composed of frozen nitrogen and methane, and its thin atmosphere is composed of similar compounds.