The universe is all of existence-all of space and time and all the matter and energy within it. The universe is unknowably vast,and ever since it formed, it has been expanding,carrying distant regions apart at speeds up to,and in some cases possibly exceeding,the speed of light.The universe encompasses everything from the smallest atom to the largest galaxy cluster,and yet it seems that all are governed by the same basic laws.All visible matter is built from the same sub atomic blocks,and the same fundamental forces govern all interactions between these elements.
THE SOLAR SYSTEM:
Eight major planets,one dwarf planet,there satellites and countless miner planets(As
teroids)orbit the Sun to form The Solar System.The Sun,our nearest star, creates energy from nuclear reactions deep within its interior,providing all the light and heat which make life on earth possible.The earth is unique in the solar system in that it supports life,its size,gravitational pull and distance from the Sun have all created the optimum conditions for the evolution of life.Orbits in the solar system:
Most orbits of objects in the solar system have the shapes of ellipses(stretched circles).However for most of the planets,these ellipses are close to being circular.Only Mercury has an orbit that differs very markedly from being circular.All the planets and nearly all asteroids orbit the Sun in the same direction,which is also the direction in which the Sun spins on its own axis.The orbital period (the time it takes a planet to orbit the Sun) increases with distance from the Sun, i.e 88 earth days for mercury to nearly 165 earth years for Neptune.The planets farther from the Sun move much more slowly.
- THE SUN
Diameter: 864,948 miles(1,392,000 km)
Mass: 1990 million million million million tons
Our local star Sun dominates the solar system(our chief source of heat and light).The Sun holds the earth and the rest of the planets in their orbits.
The Sun was formed when a swirling cloud of dust and gas contracted,pulling matter into
its center.When the temperature at the center rose to 1,000,000 degree celsius,nuclear fusion(the fusing of Hydrogen into Helium)creating energy,releasing a constant stream of heat and light.The cloud of dust and gas thrown out by the Sun during its formation cooled to form the solar system.The smaller planets nearest the Sun are formed of minerals and metals.The outer planets were formed at lower temperatures and consist of swirling clouds of gases.The Sun usually appears to the unaided eye as a
bright but featureless disc.During a total solar eclipse,when light from the disc is blocked out by the moon,violent flares in the outer layers of the atmosphere can be seen more clearly.The gas in the Sun's corona is heated to several million degrees causing it to emit X-rays.
Prominences:
In the corona,electrified gas called plasma forms into huge clouds known as prominences,flowing through the sun's magnetic field.As the prominence in this image erupts,it hurls plasma out of the sun's atmosphere and into space.
Sunspots on the solar surface(8 light-minutes from earth):
These regions are cooler and darker than the rest of the sun's surface.These are sustained by strong magnetic fields.Some sunspots are large enough to engulf the earth.Sunspot numbers vary in cycles that take about 11 years to complete and peaks in the cycle coincide with disturbances,such as aurorae.
Internal Structure:The Sun is a 4.6 billion years old main sequence star.It is a huge sphere of exceedingly hot plasma (ionized gas) containing 750 times the mass of all the solar system's planets put together.In its core nuclear reactions produce helium from hydrogen and generate colossal amounts of energy.This energy is gradually carried outwards until it eventually escapes from the Sun's surface.
The Sun has three internal layers although there are no sharp boundaries between them.The temperature and pressures are extremely high in the core,also here nuclear fusion turns the nuclei of hydrogen atoms (protons) into helium nuclei at the rate of about 600 million tons per second,this produces a high amount of energy in the form of photons of electromagnetic radiation and neutrinos (particles with no charge and almost no mass).The electromagnetic radiation travels out from the core through a slightly cooler region,the radiative zone.It takes about 1 million years to find its way out of this zone,as the photons are continuously absorbed and re-emitted by ions in the plasma.The energy wells up in convective zone where huge flows of rising hot plasma occur next to areas of falling cooler plasma and is transferred to a surface layer called photosphere.There it escapes as heat,light and other forms of radiation.Sun's Structure From Inner To Outer:Core -> Radiative zone (Where energy travels in the form of photons) -> Convective zone (It is a region where energy is carried by convection cells) -> Photosphere (The Sun's visible surface) -> Chromosphere (It is an irregular layer of atmosphere above the photosphere).
Atmosphere:
Photosphere is the lowest layer of the Sun's atmosphere.above it three atmosphere layer are present.The orangey-red chromosphere lies above the photosphere and is about 2,000 km deep.Its temperature rises from 4.500 degree celsius to about 20.000 degree celsius from bottom to top.the chromosphere contains many flame like columns of plasma called spicules.Between the chromosphere and the corona a thin irregular layer present called transition regions,within which the temperature rises from 20,000 degree celsius to about 1 million degree celsius.The outermost layer of the solar atmosphere is the corona consists of thin plasma.A stream of charged particles (photons and electrons) flowing away from the Sun across the solar system continuously.The corona is extremely hot, i,e 2 million degree celsius.Coronal mass ejections are huge bubbles of plasma,containing billions of tons of material,that are occasionally ejected from the Sun's surface through the corona into space.Coronal mass ejection can disturb the solar wind,which results in changes to aurorae in Earth's atmosphere.- THE MERCURY
Mass: 330 million million million tons
Temperature: -173 to 427 degree celsius
Distance from Sun: 36 million
Length of day: 58.65 earth days
Length of year: 87.97 earth days
Surface gravity: 1 kg=0.38 kg
Mercury is not an easy object to observe from earth,because of its close proximity to the Sun.It never reaches an elongation greater than about 27 degree.It was long supposed that its axial rotation was the same as its orbital period of 87.97 earth days so one hemisphere permanently faced the Sun,leading very high temperature while the other was always cold.Mercury has very high density greater than any of the other planets (except the earth) due to the presence of a relatively large metallic iron-nickel core,which contains about 80% of the planet mass (as compared with the Earth's 32%).The field strength of the Mercury is weaker than that of the Earth.The exact position of the magnetic axis is unknown,but it is coincide with the rotational axis.Mercury has a very tenous atmosphere which consists mainly of sodium.In addition there are helium and hydrogen atoms captured from the solar wind and retained for about 200 days before they gain sufficient energy to escape back to space.
- THE VENUS
Mass: 4870 million million million tons
Temperature: 457 degree celsius
Distance from Sun: 67 million miles (108 million km)
Length of day: 243.01 earth days
Length of year: 224.7 earth days
Surface gravity: 1kg=0.88 kg
It is the fact that Venus approaches closer to the Earth then any other major planet and that it is very similar in size and total mass to the Earth.Venus has a very extensive atmosphere with an albedo (surface reflectivity) of 76% and this completely hides the surface.Venus rotates on its axis in the opposite sense to the Earth.The main constituent of the atmosphere is carbon dioxide which amounts to 97% of the total.Because of the vast amount of carbon dioxide the atmospheric pressure is about ninety times that of the Earth.There is a direct evidence that Venus once had a considerable quantity of water.This information comes from a determination of the ratio of hydrogen to deuterium.There is far more deuterium on Venus then on Earth and this shows that a large amount of water was once present,indeed that oceans probably existed.However, it does seem likely that Venus had large bodies of water at an early period in its history,and it is by no means impossible that some form of life did originate upon the planet before the green house effect made it too hot for any life forms.In Venus the clouds exhibit a strongly layered structure,the densest layers occurring between about 70 and 47.5 km,with hazes both above and below but the lower atmosphere is essentially clear.
- THE EARTH
Mass: 5976 million million million tons
Temperature: -70 to 55 degree celsius
Distance from Sun: 93 million miles (150 million km)Length of day: 23.92 hours
Length of year: 365.25 earth days
Surface gravity: 1kg=1kg
Earth is the third closest planet to the Sun.It formed approximately 4.56 billion years ago.It is unique in the solar system that it contain water at its surface.Earth's rotation causes its equatorial regions to bulge out slightly by about 21 km compare to poles.It has a central solid part, which has a temperature of about 4700 degree celsius.Earth has a substantial magnetic field, which is caused by a swirling motion of its liquid metal outer core.The magnetic field behaves as though a large bar magnet was present within the earth, tilted at an angle to its axis of rotation.Earth is surrounded by the atmosphere, a layer of gases many hundreds of kilometers thick.The four main layers in Earth's atmosphere are distinguished by different temperature characteristics.No boundary exists at the top of the atmosphere.Earth's crust and top part of its mantle are joined in a structure called lithosphere.Most plates of the Earth carry both oceanic crust and some thicker continental crust, although a few carry only oceanic crust.Earth's plates move relative to each other as a result of convection currents within the mantle.
- THE MARS
Mass: 642 million million million tons
Temperature: -137 to 37 degree celsius
Distance from Sun: 142 million miles (228 million km)
Length of day: 24.623 hours
Length of year: 1.88 earth years
Surface gravity: 1 kg=0.38 kg
Canyons on mars:
4 light minutes from earth
Mars is one of the solar system's four inner rocky planets.
Mars has only a thin atmosphere.Mars has a lower density than any of the other inner planets and has a surface gravity almost exactly equal to that of Mercury, despite being more than 3800 km greater in diameter.Mars size and distance mean that it has cooled more rapidly than earth.Its relatively low density compared to the other terrestrial planets indicates that the core may also contain a liter element such as sulphur in the form of iron sulphide.Mars is a cold dry planet.The average surface temperature is -63 degree celsius.The thin atmosphere of Earth is dominated by carbon dioxide with tiny amounts of nitrogen and argon and other gases and some water vapour.
- THE JUPITER
Mass: 1,900,000 million million million tons
Temperature: -153 degree celsius
Distance from Sun: 483 million miles
(778 million km)
Length of day: 9.84 hours
Length of year: 11.86 earth years
Surface gravity: 1 kg=2.53 kg
Jupiter is more massive than all of the other planets.It has the shortest rotation period, it has avast magnetic field and is a powerful source of radio waves.It has at least 17 satellites and exerts great influence on the orbits of the minor planets and comets by its gravitational perturbations.Despite its great mass, its density is only a quarter that of the Earth.The extreme outer layer of the Jupiter's atmosphere consists mostly of ammonia and hydrogen with smaller amounts of methane and water.It is certain that enormously powerful winds blow in the upper atmosphere of Jupiter,this is due to the extremely rapid rotation of the planet (which revolves on its axis in only 9 hours and 15 minutes).Due to its rapid rotation a powerful counter currents of gases set up in the upper atmosphere give rise to long lasting spiralling systems.The magnetic axis is tilted by about 10 to 11 degree from the axis of ratation and displaced by about 7000 km from the center of the planet.
Jupiter's great red spot(34 light-minutes from earth):
The gas giant Jupiter is more massive than all the other planets in the solar system.It's mysterious swirling vortex,the great red spot has been known since the 17th century.The image of the great red spot was taken in 1979 by Voyager 1,using filters that exaggerate its colours.- THE SATURN
Mass: 570,000 million million million tons
Temperature: -185 degree celsius
Distance from Sun: 887 million miles (1427 million km)
Length of day: 10.23 hours
Length of year: 29.46 earth years
Surface gravity; 1 kg=1.07 kg
Generally Saturn shows many similarity to Jupiter,and is a very sizable planet with an equatorial diameter of 120000 km.It is particularly remarkable for its very low density of only 706 kg/m^3.It is primarily composed of hydrogen and helium and have a core of silicon material relatively larger than Jupiter.The whole solid core probably contains about 10 to 15 Earth masses.Saturn has an internal source of heat and that the amount of energy is relatively more important.Saturn has an even greater polar flattening than Jupiter and the polar diameter is about 108,600 km.
It is clear that the rings contain only a tiny fraction of the total mass of the Saturn and that they must consist of myriads of tiny particles orbiting about the planet.The rings can not be more than a few km thick.Titan, which is the Saturn's largest moon.
Saturn and its rings:
71 light minutes from earth
There are rings of dust and ice particles in near circular orbits around all four of the giant gas planets,but those around Saturn are especially beautiful.
- THE URANUS
Mass: 86,800 million million million tons
Temperature: -214 degree celsius
Distance from Sun: 1783 million miles (2870 million km)
Length of Day: 17.9 hours
Length of year: 84.01 earth years
Surface gravity: 1 kg=0.92 kg
Uranus is very large in size.Uranus has a temperature that agrees with that calculated for its distance, indicating that it has no major internal source of heat.Uranus is unique among the planets in that its equatorial plane is almost perpendicular to the orbital plane.The axis is tilted by an angle of about 98 degree,so that the rotation and the orbits of the satellites are retrograde.The effect of the axial inclination is that for very long periods if time (84.01 Earth year).Uranus has a very strong field is about 50 times the strength of the Earth.Its winds are stronger at a greater heights and are probably matched by flow in the opposite direction in the equatorial region.Uranus shows some auroral activity on its night side but any presence of the day side is swamped by an unusual ultraviolet "electro-glow",caused by the collision of exited electrons with hydrogen molecules high above planet at a height of about 15,00 km above the cloud tops.Uranus hags 15 satellites.Uranus and rings:
Uranus has 11 major rings and a blue coloration caused by the presence of methane in its atmosphere.Its spin axis is tilted right over on the side.
- THE NEPTUNE
Mass: 102,000 million million million tons
Temperature: -225 degree celsius
Distance from Sun: 2794 million miles (4497 million km)
Length of day: 19.2 hours
Length of year: 164.79 earth years
Surface gravity: 1kg=1.18 kg
Neptune is being about 15% more massive than Uranus.Its characteristics are more similar to that of Uranus.It is the smallest and the coldest of the four gas giants.Neptune is about 30 times farther from the Sun than Earth,and at this distance Sun is 900 times dimmer.It is too massive in relation to its size to be composed mainly of hydrogen.Neptune's magnetic field is tilted by 46.8 degree to the spin axis.This is a shallow, hydrogen rich layer that also contains helium and methane gas.The heat Neptune receives from the Sun is not enough to drive its weather so its temperature is very less.Neptune's atmosphere is lies in bands, which are parallel to the equator.
- THE PLUTO (A DWARF PLANET)
Mass: 13 million million million tons
Temperature: -236 degree celsius
Distance from Sun: 3666 million miles (5900 million km)
Length of day: 6.39 hours
Length of year: 248.54 earth years
Surface gravity: 1 kg=0.30 kg
The distance of Pluto from the Sun is so great so it is very difficult to study.The planet is covered in methane frost, such a surface layer would have n albedo of 40 to 60%,which from the known brightness.Pluto has a moon of its own, this was subsequently named Charon.The orbital period of Charon seems to be of the order of 6.39 day.The planet's orbital inclination and eccentricity are far greater than that of any other planet including Mercury.Pluto is of very low mass, so its orbital disturbances occur due to the presence of Uranus and Neptune.Pluto's density indicates that it is probably 70% rock and 30% water ice, rock has sunk to the center and water ice has formed a surface layer also nitrogen,carbon dioxide and methane are present in the atmosphere.
THE ROCKY PLANETS
The four inner planets (Mercury,Venus,Earth,Mars) of the solar system are called the rocky planets.They are much smaller than the gas giants (Jupiter,Saturn,Uranus,Neptune),have few or no Moons and no rings.All four are burn in a molten state due to the heat of the collisions that led to their formation.While molten,the materials from which they are made became separated into a metallic core and a rocky mantle and crust.
From history all these planets suffered heavy bombardment by meteorites that left craters on their surfaces,although on Earth these craters have hidden by various geological processes.Rocky planets are quite diverse from each other like Venus has a dense atmosphere consisting mainly of carbon dioxide,while Mars has a thin atmosphere composed of the same gas.But Mercury has virtually no atmosphere and Earth is rich in nitrogen and oxygen.
THE GAS GIANTS
The four large planets immediately beyond the asteroid belt are called the gas giants.Each has a core composed of rock and ice.This is surrounded by a liquid or semi-solid mantle containing hydrogen and helium, in case of Uranus and Neptune a combination of methane,ammonia,and water ices.Each has a deep,often stormy atmosphere composed mainly of hydrogen and helium.All four have a significant magnetic field,but Jupiter has 20,000 times stronger than that of Earth.Each gas giants is orbited by a large number of Moons,several dozens in case of Jupiter.All four gas giants have ring systems made of grains of rock or ice.These rings are present since planets formed and continuously attracted by powerful gravitational fields.
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THE GAS GIANTS
The four large planets immediately beyond the asteroid belt are called the gas giants.Each has a core composed of rock and ice.This is surrounded by a liquid or semi-solid mantle containing hydrogen and helium, in case of Uranus and Neptune a combination of methane,ammonia,and water ices.Each has a deep,often stormy atmosphere composed mainly of hydrogen and helium.All four have a significant magnetic field,but Jupiter has 20,000 times stronger than that of Earth.Each gas giants is orbited by a large number of Moons,several dozens in case of Jupiter.All four gas giants have ring systems made of grains of rock or ice.These rings are present since planets formed and continuously attracted by powerful gravitational fields.
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