Space and planets

By Ruby

Contents• Introduction• Earth • Mercury • Pluto • Neptune • The sun• The moon• Mars• Saturn• Jupiter • Uranus• Venus• Comets• Asteroids• The end

Earth• Earth is the third planet from the

Sun, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density. It is also referred to as the World and Terra. Earth has been referred to as the Blue Planet due to the abundant water on its surface and/or the atmospheric hue.

• Home to millions of species including humans, Earth is the only place in the universe where life is known to exist. The planet formed 4.54 billion years ago and life appeared on its surface within a billion years.

Mercury

• Mercury is the innermost and smallest planet in the Solar System orbiting the Sun once every 88 days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt.

Pluto• Pluto, is the second-largest known

dwarf planet in the Solar System (after Eris) and the tenth-largest body observed directly orbiting the Sun. Originally classified as a planet, Pluto is now considered the largest member of a distinct population called the Kuiper belt.[9]

• Like other members of the Kuiper belt, Pluto is composed primarily of rock and ice and is relatively small: approximately a fifth the mass of the Earth's Moon and a third its volume. It has an eccentric and highly inclined orbit that takes it from 30 to 49 AU (4.4–7.4 billion km) from the Sun. This causes Pluto periodically to come closer to the Sun than Neptune.

Neptune• Neptune is the eighth planet from the

Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third-largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 Earth masses and not as dense. On average, Neptune orbits the Sun at a distance of 30.1 , approximately 30 times the Earth-Sun distance. Its astronomical symbol is , a stylized version of the god Neptune's trident.

• Discovered on September 23, 1846, Neptune was the first planet found by mathematical prediction rather than by empirical observation. Unexpected changes in the orbit of Uranus led astronomers to deduce that its orbit was subject to gravitational perturbation by an unknown planet.

The sun• The Sun, a yellow dwarf, is the

star at the centre of the Solar System. The Earth and other matter (including other planets, asteroids, meteoroids, comets, and dust) orbit the Sun, which by itself accounts for about 98.6% of the Solar System's mass. The mean distance of the Sun from the Earth is approximately 149,600,000 kilometres (93,000,000 mi), and its light travels this distance in 8 minutes and 19 seconds. Energy from the Sun, in the form of sunlight, supports almost all life on Earth via photosynthesis, and drives the Earth's climate and weather.

The Moon• The Moon is Earth's only

natural satellite and the fifth largest satellite in the Solar System. The average centre-to-centre distance from the Earth to the Moon is 384,403 km, about thirty times the diameter of the Earth. The common centre of mass of the system (the barycentre) is located about 1,700 km—a quarter the Earth's radius—beneath the surface of the Earth. The Moon makes a complete orbit around the Earth every 27.3 days and the periodic variations in the geometry of the Earth–Moon–Sun system are responsible for the lunar phases that repeat every 29.5 days.

Mars• Mars (pronounced /ˈmars/) is the fourth

planet from the Sun in the Solar System. The planet is named after Mars, the Roman god of war. It is also referred to as the "Red Planet" because of its reddish appearance, due to iron oxide prevalent on its surface.

• Mars 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 is the site of Olympus Mons, the highest known mountain in the Solar System, and of Valles Marineris, the largest canyon. Furthermore, in June 2008 three articles published in Nature presented evidence of an enormous impact crater in Mars' northern hemisphere, 10,600 km long by 8,500 km wide, or roughly four times larger than the largest impact crater yet discovered, the South Pole-Aitken basin.[6][7] In addition to its geographical features, Mars’ rotational period and seasonal cycles are likewise similar to those of Earth.

Saturn• Saturn ( /ˈsætɚn/ (help·info)[10]) is the

sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn, along with Jupiter, Uranus and Neptune, is classified as a gas giant. Together, these four planets are sometimes referred to as the Jovian, meaning "Jupiter-like", planets.

• Saturn is named after the Roman god Saturn's (that became the namesake of Saturday), equated to the Greek Kronos (the Titan father of Zeus) the Babylonian Minute and to the Hindu Shani. Saturn's symbol represents the god's sickle (Unicode: ♄).

• The planet Saturn is composed of hydrogen, with small proportions of helium and trace elements.[11] The interior consists of a small core of rock and ice, surrounded by a thick layer of metallic hydrogen and a gaseous outer layer.

Jupiter • Jupiter, is the fifth planet from the Sun and

the largest planet within the Solar System. It is a gas giant with mass slightly less than one thousandth that of the Sun but is two and a half times more massive than all of the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn, Uranus and Neptune. Together, these four planets are sometimes referred to as the Jovian planets.

• The planet was known by astronomers of ancient times and was associated with the mythology and religious beliefs of many cultures. The Romans named the planet after the Roman god Jupiter. When viewed from Earth, Jupiter can reach an apparent magnitude of −2.8, making it on average the third-brightest object in the night sky after the Moon and Venus. (Mars can briefly exceed Jupiter's brightness at certain points in its orbit.)

Uranus • Uranus is the seventh planet from

the Sun and the third-largest and fourth most massive planet in the Solar System. It is named after the ancient Greek deity of the sky Uranus (Ancient Greek) the father of Kronos (Saturn) and grandfather of Zeus (Jupiter). Though it is visible to the naked eye like the five classical planets, it was never recognized as a planet by ancient observers because of its dimness and slow orbit. Sir William Herschel announced its discovery on March 13, 1781, expanding the known boundaries of the solar system for the first time in modern history. This was also the first discovery of a planet made using a telescope.

Venus • Venus is the second-closest

planet to the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love. Except for the Moon it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6. Because Venus is an inferior planet from Earth, it never appears to venture far from the Sun: its elongation reaches a maximum of 47.8°. Venus reaches its maximum brightness shortly before sunrise or shortly after sunset, for which reason it is often called the Morning Star or the Evening Star.

Comets

• A comet is a Small Solar System Body that orbits the Sun. When close enough to the Sun, a comet exhibits a visible coma (fuzzy "atmosphere"), and sometimes a tail, both because of the effects of solar radiation upon the comet's nucleus. Comet nuclei are themselves loose collections of ice, dust and small rocky particles, ranging from a few kilometres to tens of kilometres across.

Asteroids • Asteroids, sometimes called

minor planets or planetoids, are small Solar System bodies in orbit around the Sun, especially in the inner Solar System; they are smaller than planets but larger than meteoroids. The term "asteroid" has historically been applied primarily to bodies in the inner Solar System since the outer Solar System was poorly known when it came into common usage. The distinction between asteroids and comets is made on visual appearance: Comets show a perceptible coma while asteroids do not.

The End

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