Name :- W.A.Hasitha Srimal Dhananjaya
Registration Number :- EU/IS/2019/PHY/123
Index Number :- PS2873
Sunday 7 August 2022
Introduction To Our Solar System
The Solar System consists of the Sun and its planetary system of eight planets, their moons, and other non-stellar objects. It formed 4.6 billion years ago from the gravitational collapse of a giant molecular cloud. The vast majority of the system’s mass is in the Sun, with most of the remaining mass contained in Jupiter.
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 two largest, Jupiter and Saturn, are composed mainly of hydrogen and helium; the two outermost planets, Uranus and Neptune, are composed largely of substances with relatively high melting points (compared with hydrogen and helium), called ices, such as water, ammonia and methane, and are often referred to separately as “ice giants”.
All planets have almost circular orbits that lie within a nearly flat disc called the ecliptic
The Birth Of The Solar System
The origin of the Sun and of the Solar System is connected to the condensation of a primordial cloud of gas and dust as those often seen in our galaxy. It is probable that an external event triggered the collapse of the cloud, since its parts were in equilibrium. Scientists have put forward the hypothesis that it could have been the explosion of a nearby supernova, i.e. a star with a great mass that has an explosive death expelling all its atmosphere into space. The silent shock wave must have given the cloud the initial push: so the death of a star can bring about the birth of another star.Once the collapse has been triggered off it proceeds on its own: as the distance between the matter that composes the cloud diminishes, a stronger gravitational force is generated which tends to pull the mass together. The free-falling matter does not fall in a straight line towards the centre, but rotates around it in tighter and tighter spirals. Both the rotation of the Sun and the planets around their axis, and the revolution of the planets and other bodies around the Sun are a consequence of this initial vortex.
As the collapse proceeded, most of the cloud matter concentrated in the central regions reaching the density and temperature required to form a star, a body capable of producing and emitting energy on its own. On the edge of the cloud, instead, the remaining matter continued to rotate around the centre, thinned into the shape of a disc, and formed the planets from the dust grains present, through collisions and successive aggregations. Still today, the main bodies of the Solar System rotate around our star on the same plane, which is called the ecliptic. Scientists believe that the asteroids, frozen bodies and dust that are present in our planetary system represent the oldest residues of its formation; in other words, they are the result of primordial aggregations that were not able to evolve into planets. The fact that their orbits are more inclined respect to the ecliptic plane testifies that these bodies were excluded from the main formation mechanism that took place along the rotation disc.
Today the Sun has been burning for 5 billion years and will continue to do so for another 5 billion more. Once all the hydrogen, its main fuel, is consumed, it will expand into a red giant, engulfing the entire Solar System up to Mars’ orbit (the Earth is included!). Subsequently, it will shed its outer layers in a gust of gas and it will enter the final phase of its life cycle changing into a white dwarf, a small dimly luminous star destined to get cold and to slowly die off.
Sun
The sun is a yellow dwarf star in the center of the solar system , and it is the largest, brightest and most massive object in the system.
The sun formed around 4.5 billion years ago. At that time, the area of the Milky Way galaxy that would become the solar system consisted of a dense cloud of gas the remnants of an earlier generation of stars. The densest region of this cloud collapsed and gave rise to the protostar that would become the sun. As this young protostar grew, planets, moons and asteroids formed around it from what remained of this raw material, bound in orbit to their parent star by its immense gravity.
At the heart of the sun, this same force sparked nuclear fusion that powers the star. The heat and light from this nuclear reaction enabled life on Earth to evolve and prosper. However, this reaction will eventually lead to the sun’s demise, as the sun will eventually run out of nuclear fuel.
WHAT IS THE SUN MADE OF?
The sun is in the period of a stellar body's life in which it fuses hydrogen to create helium. The difference in mass between the hydrogen atoms and the daughter helium atom is released as energy — the heat and light that sustain our planet. This is called the main sequence.
Before the main sequence stars like the sun exist as what is known as protostars, gathering mass from their surroundings and growing to the mass required to initiate fusion.
Like all main-sequence stars, the majority of the sun's mass is made up of hydrogen, with some helium and traces of heavier elements , which are referred to as the metallicity or “Z” of a star (the astronomical definition of a metal is "any element heavier than helium").
The ratio of the sun's mass is 73% hydrogen, 25% helium, and 2% metals. The generations of stars that preceded the sun would have had smaller ratios of metals than this, enriching their galaxies with heavier elements upon their deaths.
The larger a star is, the more rapidly it burns through its hydrogen content; some of the largest stars such as those with masses 40 times that of the sun — have lifetimes as short as a million years compared to the Sun's main-sequence lifetime of around 10 billion years, according to Swinburne University of Technology in Australia
How Hot Is The Sun?
Yet the core of the sun and this powerful engine is out of sight. The deepest part of the sun that we see on Earth is the photosphere, which loosely passes as a "surface" for this ball of plasma. The temperature of the photosphere ranges from around 6,700 F to 14,000 F (3,700 C to 7,700 C).
Above the photosphere is the loose, tenuous atmosphere of the sun, known as the corona. The corona isn't visible from Earth under ordinary conditions as the light it emits is overwhelmed by that of the photosphere. The corona, however, represents one of the most significant mysteries surrounding the sun.
Scientists’ theoretical models of stars suggest they should become hotter as one moves towards their center as is seen in regions of the sun between the photosphere and core, called the chromosphere and the transition region, where temperatures rise sharply to 900,000 F (500,000 C), according to NASA
Yet, the corona at a temperature of around 900,000 F or more, is actually many times hotter than the photosphere 1,300 miles (2,100 km) below it.
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Neptun
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Neptune is the eighth planet from the sun in our solar system
. This blue gas giant is far larger than Earth, at more than 17 times Earth's mass and nearly 58 times Earth's volume, according to NASA. Neptune's rocky core is surrounded by a slushy fluid mix of water, ammonia and methane ice.
Astronomer Galileo Galilei was one of the first people to identify Neptune as a space object, however he assumed it was a star based on its slow movement. Around two hundred years later, in 1846, French astronomer Urbain Jean Joseph Le Verrier calculated the approximate location of Neptune by studying gravity-induced disturbances in the motions of Uranus according to a synopsis written by researchers at the University of St. Andrews in Scotland
At the same time Le Verrier was calculating the existence of Neptune, so was English astronomer John Couch Adams. The two scholars independently came up with nearly identical mathematical predictions about Neptune's existence. Le Verrier then informed his colleague, German astronomer Johann Gottfried Galle, about his calculations, and Galle and his assistant Heinrich d'Arrest, confirmed Le Verrier's predictions by viewing and identifying Neptune through the telescope at his observatory in Berlin.
In accordance with all the other planets seen in the sky, and as suggested by Le Verrier, this new world was given a name from Greek and Roman mythology — Neptune, the Roman god of the sea.
Neptune's Moons
Neptune has 14 known moons, named after lesser sea gods and nymphs from Greek
mythology. The largest by far is Triton whose discovery on Oct. 10, 1846, was indirectly enabled by beer — amateur astronomer William Lassell, who discovered Triton, used the funds he made as a brewer to finance his telescopes.
mythology. The largest by far is Triton whose discovery on Oct. 10, 1846, was indirectly enabled by beer — amateur astronomer William Lassell, who discovered Triton, used the funds he made as a brewer to finance his telescopes.
Uranus
Average temperature: -195°C (-320°F) where atmospheric pressure equals sea level on EarthAverage distance from Sun: 2,873 million kilometers (1,785 million miles), or 19 times farther from the Sun than Earth
Diameter: 51,118 kilometers (31,763 miles), Uranus is 4 times wider than Earth
Volume: 68 trillion km3 (16 trillion mi3), Earth could fit inside Uranus 68 times
Gravity: 8.7 m/s², or 89% that of Earth’s
Solar day: 17 Earth hours
Solar year: 30,687 Earth days
Atmosphere: 83% hydrogen, 15% helium, 2% methane and other gases
Uranus' climate
The extreme axial tilt Uranus experiences can give rise to unusual weather. As sunlight reaches some areas for the first time in years, it heats up the atmosphere, triggering gigantic springtime storms, according to NASA.
However, when Voyager 2 first imaged Uranus in 1986 at the height of summer in its south, the spacecraft saw a bland-looking sphere with only about 10 or so visible clouds, leading to it to be dubbed "the most boring planet," wrote astronomer Heidi Hammel in "The Ice Giant Systems of Uranus and Neptune," a chapter in "Solar System Update" (Springer, 2007), a compilation of reviews in solar system science. It was decades later, when advanced telescopes such as Hubble came into play and Uranus' long seasons changed, before scientists witnessed the extreme weather on Uranus.
In 2014, astronomers got their first glimpse at summer storms raging on Uranus. Strangely, these massive storms took place seven years after the planet reached its closest approach to the sun, and it remains a mystery why the giant storms occurred after the sun’s heating on the planet was at a maximum.
Other unusual weather on Uranus includes diamond rain, which is thought to sink thousands of miles below the surface of icy giant planets such as Uranus and Neptune. Carbon and hydrogen are thought to compress under extreme heat and pressure deep in the atmospheres of these planets to form diamonds, which are then thought to sink downward, eventually settling around the cores of those worlds.
Saturn
Saturn is the sixth planet from the sun and the second-largest planet in the solar system. It's the farthest planet from Earth that's visible to the naked human eye, but the planet's most outstanding features its rings are better viewed through a telescope. Although the other gas giants in the solar system Jupiter, Uranus and Neptune also have rings, Saturn's rings are particularly prominent, earning it the nickname the "Ringed Planet."
Physical Characteristics Of Saturn
Saturn is a gas giant made up mostly of hydrogen and helium. Saturn's volume is greater
than 760 Earths, and it is the second most massive planet in the solar system, about 95 times Earth's mass. The Ringed Planet is the least dense of all the planets, and is the only one less dense than water. If there were a bathtub big enough to hold it, Saturn would float.
The yellow and gold bands seen in Saturn's atmosphere are the result of superfast winds in the upper atmosphere, which can reach up to 1,100 mph (1,800 km/h) around its equator, combined with heat rising from the planet's interior. Saturn rotates about once every 10.5 hours. The planet's high-speed spin causes Saturn to bulge at its equator and flatten at its poles. The planet is around 75,000 miles (120,000 kilometers) across at its equator, and 68,000 miles (109,000 km) from pole to pole.
Saturn' Rings
Galileo Galilei was the first to see Saturn's rings in 1610, although from his telescope the rings looked more like handles or arms. Forty five years later, in 1655, Dutch astronomer Christiaan Huygens, who had a more powerful telescope, later proposed that Saturn had a thin, flat ring.
Saturn's Moons
Saturn has at least 62 moons. The largest, Titan, is slightly larger than Mercury, and is the second-largest moon in the solar system behind Jupiter's moon Ganymede (Earth's moon is the fifth largest).
Some of the moons have extreme features. Pan and Atlas are shaped like flying
saucers; Iapetus has one side as bright as snow and one side as dark as coal. Enceladus shows evidence of "ice volcanism": a hidden ocean spews out water and other chemicals from the 101 geysers spotted at the moon's southern pole. A number of these satellites, such as Prometheus and Pandora, are referred to as shepherd moons because they interact with ring material and keep the rings in their orbits.
Though scientists have identified many moons, Saturn has other small moons constantly being created and destroyed.
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The origin of the Sun and of the Solar System is connected to the condensation of a primordial cloud of gas and dust as those often seen...