Monday, December 5, 2011

Current Issue about the Solar System

By the end of the International Astronomical Union (IAU) General Assembly on 24 August 2006 at Prague,the IAU therefore resolves that planets and other bodies,except satellites,in our solar system be defined into three distinct categories in the following way:

1.A planet is a celestial body that:

a) is in orbit is round the Sun,

b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assume a hydrostatic equilibrium (nearly round) shape,and

c) has cleared the neighbourhood around its orbit

The eight "planets" are Mercury,Venus,
Earth,Mars,Jupiter,Saturn,Uranus and Neptune.

2. A "dwarf" planet is a celestial body that:
a) is in orbit around the Sun

b) has sufficient mass for its self-gravity to        overcome rigid body forces so that it assumes a hdyrostatic equilibrium (nearly round) shape.

c) has not cleared the neighbourhood around its orbit.

d) is not a satellite

Solar system objects now classified as dwarf planets are,Ceres,Pluto,Eris,Makemake an Haumea.

3. "small solar system Bodles" referrd all other objects (solar system asteroids,most Trans-Neptunian Objects (TNOa),comets,and other small bodies axcept satellites orbiting the sun.

Sunday, December 4, 2011


Pluto is named after the Greek God of the under world. Pluto is the only planet in the Solar System which has not been visited by a spacecraft. The orbit of Pluto is the most elliptical of all the planets and in 1989 it was 'perihelion', when it come closer to the Sun than Neptune. Pluto is so small that it is only about one-sixth of the diameter of the Earth. 

Characteristics of Pluto
                                                      Mass : 11.9421kg
                                                      Radius : 1,150 kg
                                                    Mean dansity : 2.0 g 


Neptune is an apparent twin of Uranus internally, composed of hydrogen and helium, but with much more carbon, nitrogen, and oxygen than Jupiter and Saturn. The outermost of the four 'gas giant' planets, discovered in the year 1846 as a result of a prediction by the French astronomer Urbain Leverrier. There are at least 13 moons, including Triton, which has thin atmosphere, and Nereid
 Characteristics  of  Neptune
1. Mass   : 102.7 x 1024 kg
2.  Radius : 24,750 km
3. Mean density  : 1.7g/cm3
4.Rotational Period   : 0.67 days

Saturday, December 3, 2011


Uranus is surrounded by a thick atmosphere of helium,hydrogen and methane.But unlike the other "cloudy" planets it has hardly any cloud markings. The most exciting thing about Uranus is the tilt of its axis.The axis is so tipped over that during its "year" the sun can shine almost overhead at each pole,and parts of its surface are bathed in continuosus day,and then continuous night,for almost 40 years.

Characteristics  of  Uranus
1. Mass   :8.7 x 10 25 kg
2. Polar Radius : 25,500 km
3. Mean density  : 1.3 g / cm3
4.Rotational Period   : 17.2 h
5. Orbital period         : 84.01 years
6. Mean distance from the Sun  : 2.87 billion Km 


Saturn used to be known as the planet with 'the rings'. Ring systems have now discovered around three neighbouring planets but Saturn's rings are by far the brightest. This planet rotates very fast but not faster than Jupiter and this rapid rotation causes it to bulge at its equator and flatten at its poles.
Rings of Saturn
The rings of Saturn were observed close up by Voyager sapcecraft.The rings have particle-size distribution ranging up to several meters.They are probably made of water ice-possibly created by break up of a moon which came too near Saturn.The rings show a complex structure including several divisions and innumerable 'ringlets".

Characteristics  of  Saturn
1. Mass   : 5.69 x 1026 kg
2. Polar Radius : 53,500 km
3. Mean density  : 0.69 g / cm3
4. Equatorial radius  : 60,000 km
5. Rotational Period   : 10 h 14 min
6. Orbital period         : 29.5 years
7. Mean distance from the Sun  : 1,427 million Km 



Jupiter is the largest planet in the Solar System. It is so large that thousand Earths could fit inside it.But it spins so fast that its day is less than 10 hours long. This rapid spin has made its equator bulge outwards.

Moons of Jupiter 
The Jovian moons number more than 60,including the four large satellites namely Callisto,Europa,Io,Ganymede discovered by Galileo,which are distinct worlds in themselves and lie in near-circular orbits in an equatarial plane.

Characteristics  of  Jupiter
1. Mass   : 1.901 x 1027 kg
2. Radius : 66,750 km 
3. Mean density  : 1.33 g / cm3
4. Equatorial radius  : 71,400 km 
5. Rotational Period   : 9 h 55 min 41 s 
6. Orbital period         : 11.9 years 
7. Mean distance from the Sun  : 778.34 million Km 


Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. 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 highest known mountain within the Solar System, and of Valles Marineris, the largest canyon. The smooth Borealis basin in the northern hemisphere covers 40% of the planet and may be a giant impact feature.Mars can easily be seen from Earth with the naked eye. Its apparent magnitude reaches −3.0 a brightness surpassed only by Jupiter, Venus, the Moon, and the Sun. Optical ground based telescopes are typically limited to resolving features about 300 km (186 miles) across when Earth and Mars are closest, because of Earth's atmosphere.

Characteristics  of  Mars
1. Mass   : 6.24 x 1023 kg
2. Mean density  : 3.93 g/cm3
3. Equatorial gravity  : 372 cm/ s 
4. Rotational Period   : 24h 37min 22s
5. Orbital period         : 687 days
6. Mean distance from the Sun  : 228 million km 
7. Radius : 3,393 km


Earth formed 4.54 billion years ago, and life appeared on its surface within one billion years.The planet is home to millions of species, including humans. Earth's biosphere has significantly altered the atmosphere and other abiotic conditions on the planet, enabling the proliferation of aerobic organisms as well as the formation of the ozone layer which, together with Earth's magnetic field, blocks harmful solar radiation, permitting life on land.The physical properties of the Earth, as well as its geological history and orbit, have allowed life to persist during this period. The planet is expected to continue supporting life for at least another 500 million years.
Earth's outer surface is divided into several rigid segments, or tectonic plates, that migrate across the surface over periods of many millions of years. About 71% of the surface is covered by salt water oceans, with the remainder consisting of continents and islands which together have many lakes and other sources of water that contribute to the hydrosphere. Earth's poles are mostly covered with solid ice (Antarctic ice sheet) or sea ice (Arctic ice cap). The planet's interior remains active, with a thick layer of relatively solid mantle, a liquid outer core that generates a magnetic field, and a solid iron inner core.
Earth interacts with other objects in space, especially the Sun and the Moon. At present, Earth orbits the Sun once every 366.26 times it rotates about its own axis, which is equal to 365.26 solar days, or one sidereal year. The Earth's axis of rotation is tilted 23.4° away from the perpendicular of its orbital plane, producing seasonal variations on the planet's surface with a period of one tropical year (365.24 solar days). Earth's only known natural satellite, the Moon, which began orbiting it about 4.53 billion years ago, provides ocean tides, stabilizes the axial tilt, and gradually slows the planet's rotation. Between approximately 3.8 billion and 4.1 billion years ago, numerous asteroid impacts during the Late Heavy Bombardment caused significant changes to the greater surface environment.

Characteristics  of  Earth

1. Mass   : 5.97 x 1024 kg
2. Radius : 6,378 km
3. Mean density  : 5.52 g / cm3
4. Mean distance from the Sun  : 149.6 million Km
5. Orbital period         : 365.26 days

Friday, December 2, 2011


Venus is the planet that orbits the Sun between the Earth and Mercury, and is almost exactly the same size as the Earth. But it is very different from our planet. The surface of Venus is the hottest place in the Solar System, with a temperature reaching 4800c

It is rocky wind-swept planet with an 'atmosphere' that would feel thicker than ocean water at a depth of several hundred metres.

This atmosphere contains carbon dioxide, sulphuric acid and other poisonous compounds, and lightning flickers between the clouds.

Characteristics  of  Venus
1. Mass   : 4.87 x 1024 kg
2. Radius : 6,051 km
3. Mean density  : 5.2 g / cm3
4. Equatorial gravity  : 860 cm / s2
5. Rotational Period   : 243 days (retrograde)
6. Orbital period         : 224.7 days
7. Mean distance from the Sun  : 108.2 million Km 


Mercury is the innermost and smallest planet in the Solar System,orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits. The perihelion of Mercury's orbit precesses around the Sun at an excess of 43 arcseconds per century, a phenomenon that was explained in the 20th century by Albert Einstein's General Theory of Relativity.Mercury is bright when viewed from Earth, ranging from −2.3 to 5.7 in apparent magnitude, but is not easily seen as its greatest angular separation from the Sun is only 28.3°. Since Mercury is normally lost in the glare of the Sun, unless there is a solar eclipse it can be viewed from Earth's Northern Hemisphere only in morning or evening twilight, while its extreme elongations occur in declinations south of the celestial equator, such that it can be seen at favorable apparitions from moderate latitudes in the Southern Hemisphere in a fully dark sky.

Characteristics of Mercury

1. Mass       : 3.30 x 10 26 g

2. Radius    : 2,439 km

3. Mean density  :5.4 g / cm

4.Rotational period  : 58.65 days

5. Orbital period       : 88 days

6. Mean distance from the Sun : 57.9 million km

The Sun

The Solar System

The world 'solar' means 'to do with the Sun'. The Sun and all the things in orbit around it make up the Solar System. It comprises a family of nine planets, most of which have one or more moons.Lost of other smaller objects, such as asteroids (minor planets) and comets, also travel around the Sun. The Sun, which is a star, is by far the largest body in the Solar System. The nine planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.  

The head of the Solar System

The Sun is a huge ball of hot gas. It is 150 million kilometres away from the Earth. Sun is an ordinary star, like the thousands of others you see in the night sky. Without it life is not possible on Earth. People on the Earth have always recognized the importance of the Sun and have often worshiped it as God.

Brightness of the Sun

To many astronomers who study quasars, pulsars, white dwarfs, red giants, black holes, and other exotic members of the Universe, the Sun is a fairly dull, average sort of star.

It is but one of one hundred thousand million stars in the Milky Way    
galaxy, which is but one of the billions of  galaxies in the Universe. It appears very bright to us only because it is by far our closest star, the next closest is Alpha Centauri which is more than 250,000 times further away.         


Thursday, December 1, 2011

Solar system

          The Sun,Mercury,Venus,Earth,Mars,