Let’s answer some questions before reading this article.
1. What is a solar system?
2. What comprises a solar system?
3. In which planet do we live?
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THE SOLAR SYSTEM
The Solar System consists of the Sun and its planetary system of eight planets, their satellites, and other non-stellar objects(some smaller objects such as asteroids, comets and meteoroids). It was created 4.6 billion years ago from the gravitational collapse of a giant molecular cloud. The solar system is composed of eight planets namely: Mercury, Mars, Earth, Venus, Jupiter, Saturn, Uranus and Neptune. The four smaller inner planets, Mercury, Venus, Earth and Mars, also called the terrestrial planets, are primarily composed of rock and metal. The four outer planets, called the gas giants, are substantially more massive than the terrestrials. The solar system is also composed of meteors, asteroids, and comets.
Sun is a big star at the center of the solar system. It is almost perfectly spherical in shape and has a magnetic field around it. It has a diameter of about 1,392,684 km, about 109 times that of Earth, and its mass (about 2×1030 kilograms, 330,000 times that of Earth) accounts for about 99.86% of the total mass of the Solar System. Chemically, about three quarters of the Sun’s mass consists of hydrogen, while the rest is mostly helium. The remainder (1.69%, which nonetheless equals 5,628 times the mass of Earth) consists of heavier elements, including oxygen, carbon,neon and iron, among others.
The Sun formed about 4.6 billion years ago from the gravitational collapse of a region within a large molecular cloud. Most of the matter gathered in the center, while the rest flattened into an orbiting disk that would become solar sysytem.
The Eight Planets
Mercury is the innermost planet in the Solar system. It is also the smallest of the eight planets.It orbits the Sun once in about 88 Earth days, completing three rotations about its axis for every two orbits. The planet is named after the Roman God Mercury , the messenger to the gods. Mercury’s surface is heavily cratered and similar in appearance to Earth’s moon, indicating that it has been geologically inactive for billions of years. Due to its near lack of an atmosphere to retain heat, Mercury’s surface experiences the steepest temperature gradient of all the planets, ranging from a very cold 100 K at night to a very hot 700 K during the day.
Venus is the second planet from the Sun, orbiting it every 224.7 days. The planet is named after the Roman Goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows.Because Venus is an inferior planet from Earth, it never appears to venture far from the Sun. It is also referred to as the evening or morning star.Venus is classified as a terrestrial planet and is sometimes called Earth’s “sister planet” owing to their similar size, gravity, and bulk composition (Venus is both the closest planet to Earth and the planet closest in size to Earth).
Earth is the third planet from the sun. It is also the planet we live on. It is also the fifth largest planet in the solar system.Earth formed approximately 4.54 billion years ago, and life appeared on its surface within one billion years.
Earth’s biosphere then significantly altered the atmosphere and other basic physical conditions, which enabled the proliferation of organisms as well as the formation of the ozone layer, which together with Earth’s magnetic field blocked harmful solar radiation, and permitted formerly ocean-confined life to move safely to land.The physical properties of the Earth, as well as its geological history and orbit, have allowed life to persist.
Mars is the fourth planet from the Sun and the second smallest planet in the Solar System. Named after the Roman god of war, it is often described as the “Red Planet”, as the iron oxide prevalent on its surface gives it a reddish appearance.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. The rotational period and seasonal cycles of Mars are likewise similar to those of Earth, as is the tilt that produces the seasons. Mars is the site of Olympus Mons, the second highest known mountain within the Solar System (the tallest on a planet), and of Valles Marineris, one of the largest canyons. The smooth Borealis basin in the northern hemisphere covers 40% of the planet and may be a giant impact feature. Mars has two known moons, Phobos and Deimos, which are small and irregularly shaped. These may be captured asteroids , similar to 5261 Eureka, a Martian trojan asteroid.
Jupiter is the fifth planet from the Sun and the largest planet in the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in the 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 or outer 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 anapparent magnitude of −2.94, making it on average the third-brightest object in the night sky after the Moon and Venus. (Mars can briefly match Jupiter’s brightness at certain points in its orbit.)
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Named after the Roman god Saturn, its astronomical symbol (♄) represents the god’s sickle. Saturn is a gas giant with an average radius about nine times that of Earth. While only one-eighth the average density of Earth, with its larger volume Saturn is just over 95 times more massive than Earth.
Saturn’s interior is probably composed of a core of iron, nickel and rock (silicon and oxygen compounds), surrounded by a deep layer of metallic hydrogen, an intermediate layer of liquid hydrogen and liquid helium and an outer gaseous layer.The planet exhibits a pale yellow hue due to ammonia crystals in its upper atmosphere. Electrical current within the metallic hydrogen layer is thought to give rise to Saturn’s planetary magnetic field, which is slightly weaker than Earth’s and around one-twentieth the strength of Jupiter’s. The outer atmosphere is generally bland and lacking in contrast, although long-lived features can appear. Wind speeds on Saturn can reach 1,800 km/h (1,100 mph), faster than on Jupiter, but not as fast as those on Neptune.
Neptune is the eighth and farthest planet from the Sun in the Solar System. It is the fourth-largest planet by diameter and the third-largest by mass. Neptune is 17 times the mass of Earth and is somewhat more massive than its near-twin Uranus, which is 15 times the mass of Earth but not as dense. On average, Neptune orbits the Sun at a distance of 30.1 AU, approximately 30 times the Earth–Sun distance. Named for the Roman god of the sea, its astronomical symbol is ♆, a stylised version of the god Neptune’s trident.
Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. Uranus is similar in composition to Neptune, and both are of different chemical composition than the larger gas giants Jupiter and Saturn. For this reason, astronomers sometimes place them in a separate category called “ice giants”. Uranus’s atmosphere, while similar to Jupiter’s and Saturn’s in its primary composition of hydrogen and helium, contains more “ices” such as water, ammonia, and methane, along with traces of hydrocarbons. It is the coldest planetary atmosphere in the Solar System, with a minimum temperature of 49 K (−224 °C). It has a complex, layered cloud structure, with water thought to make up the lowest clouds, and methane thought to make up the uppermost layer of clouds. In contrast, the interior of Uranus is mainly composed of ices and rock.
OTHER BODIES IN THE SOLAR SYSTEM
Asteroids are small Solar System bodies or dwarf planets that are not comets. The term asteroids historically referred to objects inside the orbit of Jupiter. They have also been called planetoids, especially the larger ones. These terms have historically been applied to any astronomical object orbiting the Sun that did not show the disk of a planet and was not observed to have the characteristics of an active comet, but as small objects in the outer Solar System were discovered, their volatile-based surfaces were found to more closely resemble comets, and so were often distinguished from traditional asteroids.Thus the term asteroid has come increasingly to refer specifically to the small bodies of the inner Solar System within the orbit of Jupiter, which are usually rocky or metallic. They are grouped with the outer bodies—centaurs, Neptune trojans, and trans-Neptunian objects—as minor planets, which is the term preferred in astronomical circles. In this article the term “asteroid” refers to the minor planets of the inner Solar System.
A comet is an icy small Solar System body (SSSB) that, when close enough to the Sun, displays a visible coma (a thin, fuzzy, temporary atmosphere) and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet. Comet nuclei range from a few hundred meters to tens of kilometers across and are composed of loose collections of ice, dust, and small rocky particles. Comets have been observed since ancient times.
Comets have a wide range of orbital periods, ranging from a few years to hundreds of thousands of years. Short-period comets originate in the Kuiper belt, or its associated scattered disc,which lie beyond the orbit of Neptune. Longer-period comets are thought to originate in the Oort cloud, a hypothesized spherical cloud of icy bodies in the outer Solar System. Long-period comets plunge towards the Sun from the Oort cloud because of gravitational perturbations caused by either the massive outer planets of the Solar System (Jupiter, Saturn, Uranus, and Neptune), or passing stars. Rare hyperbolic comets pass once through the inner Solar System before being thrown out into interstellar space along hyperbolic trajectories. Exocomets, comets beyond our solar system, have also been detected and may be common in the Milky Way Galaxy.
A meteoroid is a sand- to boulder-sized particle of debris in the Solar System. The visible streak of light from a meteoroid, heated as it enters a planet’s atmosphere, and the glowing particles that it sheds in its wake is called a meteor, or colloquially a “shooting star” or “falling star”. Many meteors appearing seconds or minutes apart, and appearing to originate from the same fixed point in the sky, are called a meteor shower. The root word meteor comes from the Greek meteōros, meaning “suspended in the air”. Objects larger than several meters can explode in the air and create damage. If a meteoroid reaches the ground and survives impact, then it is called a meteorite.
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1. What is a solar system?
2. What are the components of a solar system?
3. On what planet do we live on?
4. What are the eight planets?
5. What are the other components of a solar system aside from planets and the sun?