A solar flare is a violent explosion that takes place on the surface of the sun. The energy released as a result of this explosion is equivalent to that caused by millions of hydrogen bombs. These flares are caused due to the sudden release of the magnetic energy stored within the solar surface. This magnetic energy heats up and accelerates the protons and neutrons resulting in explosion. Solar flares occur in three stages. The first stage is the precursor stage during which the magnetic energy is released. The second stage is the impulsive stage where the protons and the neutrons are accelerated with the release of radio waves, x rays and gamma rays. The final stage is the decay stage where the x rays begin to decay gradually. Solar flare occurs in the outermost surface of the sun called corona. They appear as bright loops in the areas of strong magnetic field called active regions. Hence sun spots tend to appear in active region. Depending on the magnetic flux the solar flares are classified as A, B, C, M and X. Solar flares results in release of clusters of accelerated particles known as proton storm. Proton storm is very hazardous as they may cause biochemical damage to human body. Solar flares are not visible to naked eye, but the radiations released can be seen with the help of some scientific instruments.
ECLIPSE
Posted by : anand
on 09:02
An eclipse occurs when the light of one celestial body is obscured by the other. With respect to earth, eclipse can be of two types- solar eclipse and lunar eclipse. These can be further classified into-total eclipse, partial eclipse, annular eclipse and hybrid eclipse. For these eclipses to occur, the sun, earth and moon must be aligned in a straight line. Solar eclipse occurs when the moon comes in between the sun and the earth, blocking the light of the sun. It occurs two to four times in a year, but only during a full moon day. A total eclipse occurs when the moon completely obscures the light from the sun. During annular eclipse the moon remains at quite a large distance from the sun. Hence the sun is not completely obscured and appears as a bright ring. An eclipse may appear as total eclipse at some place of the earth and as annular eclipse at some other place. Such eclipses are called hybrid eclipses and are very rare. Sometimes the sun and the moon do not lie in the same line resulting in partial eclipse. Lunar eclipse is witnessed when the moon passes through the earth’s shadow. It occurs only when there is a full moon with the earth lying between the sun and the moon. Unlike solar eclipse, lunar eclipse can be seen at any point on the earth’s surface and lasts for more than an hour.
WHITE DWARF
Posted by : anand
on 09:01
White dwarf is the final evolutionary stage of all stars whose mass is not too large. These are very small, faint stars which have undergone gravitational collapse and possess no energy since fusion reactions no longer occur. The faint luminosity of these stars is due to the emission of thermal energy. These stars are very dense with the density ranging from107-1011 kg/m3. These stars primarily consist of electron degenerate matter and are generally made of carbon and oxygen although some white dwarfs may be composed of neon and helium also. The composition of the White Dwarf will vary depending upon the initial mass of the star. Electrons are removed from the constituent atoms and it is the pressure exerted by these densely packed electrons which prevents further contraction of the star. White dwarfs were first noticed in the year 1910 and were given the name ‘White Dwarf’ in the year 1922 by William Luyten. When a star has become a white dwarf its temperature is higher than 100,000K. After about a billion years of its formation its temperature can be of the order of 6000K. Over a long period of time white dwarfs emit all their energy and begin to radiate in the red band of the spectrum. Finally they cool down to temperatures at which their radiation is no longer visible and become Black Dwarfs.
METEORITES
Posted by : anand
on 08:59
Meteoroids are small heavenly bodies which revolve around the sun. Those meteoroids which reach the surface of the earth without getting completely deteriorated are called meteorites. When the meteoroids enter the earth’s atmosphere, due to immense pressure they get converted to fire balls called meteors. They are also known as shooting stars and appear as a streak of light in the sky. With reference to the composition of the meteorites they a broadly classified into three types: stony meteorite, iron meteorite and stony iron meteorite. Stony meteorites are usually made of silicon. Chondrites and Achondrites are some of the most common stony meteorites. Iron meteorites are mainly composed of iron with nickel in small proportion. Stony iron meteorites are made up of both silica and iron. The motion of the meteorites is influenced by the earth’s gravitational effect. A very dense collection of meteors are formed by the deterioration of the comets. When the earth’s orbit crosses this meteor stream, large number of meteors enters the earth’s surface resulting in meteor rain. The meteorites are often recovered and preserved for research on their origin.A meteorites known as ALH84001, is believed to show evidence of life on mars.
A HUGE INVISIBLE MASS
Posted by : anand
on 08:56
For ages no one believed the greatest brain on earth, Albert Einstein about the existence of blackholes. But observations by astronomers and analysis by mathematicians have indeed proven to a great accuracy that even our own Milky Way galaxy consists of millions of blackholes. These are nothing but certain stars that lose all their fuel gradually and are no longer able to support their core as a result of which the core collapses to a single spot sometimes smaller than an atom's nucleus in a fraction of a second. The effect is that they exhibit an enormous gravitational force which is so strong that nothing can escape from the blackhole. It even traps light which is why it is called a blackhole. They are also known to emit X ray radiation which is being used by NASA to detect them. The smallest blackhole identified by NASA so far belongs to the XTE J1650-500 binary system in the Milky Way galaxy. It has a mass which is just about 3.8 times that of the sun. Being a small one it is bound to exert great tidal forces. It is a normal star and relatively lightweight. Astronomers detected the blackhole by using variations in X-ray intensity which refers to QPO.
THE SPACE SEGMENT
Posted by : anand
on 08:55
“Why do we need space segment in satellite?”. “Is it mandatory to have space segment in satellite?” .Space segment include the satellites and it also includes ground facilities needed to keep the satellites operational, by Tracking, Telemetry and Command (TT&C) facilities. The space segment has the Payload refers to the equipment used to provide the service for which the satellite has been launched. It has power supply, attitude control, Thermal control, Transponder and antennas. The primary electrical power for operating the electronic equipment is obtained by solar cells. The attitude of the satellite refers to its orientation in space. Attitude control is necessary and it can be spin stabilization or momentum wheel stabilization. The Thermal Control helps to maintain the temperature of satellite to an optimum level to avoid the satellite from damaging due to the nature of earth’s albedo. The Uplink and Downlink frequency are usually kept different in order to avoid interferences between the two signals. The transponder is the series of interconnected units which forms the single communication channel between the receiving and transmitting antennas in communication satellite. It has Band pass filter for receiving desired frequency of signals, Wide band receiver which converts the received frequency to a lower downlink frequency and then amplifies it with Power amplifier. The space segment has receiving and transmitting antenna for reception and transmission of uplink and downlink frequencies respectively from the earth segment.
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