>Various Types of Astronomies


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Modern astronomy began with the Italian astronomer Galileo. In 1609 Galileo heard of the telescope made by the Duchaman Hans Lippershey. Galileo improved upon it and constructed a similar instrument that could magnify up to thirty diameters. Various types of astronomies include the following-


Optical Astronomy-it was this thirty diameter instrument, known as ‘Refractor Telescope’, that opened the field of Optical Astronomy. Galileo made several discoveries. He found that the Moon’s surface to be rugged and the Pleiades to contain over 40 stars. He discovered four of Jupiter’s moons and observed the sunspots.
In 1668 Newton invented a new instrument ‘the Reflector Telescope’. In this, the light is gathered by a large objective lens. In a reflector telescope, a large curved mirror is used for this purpose. Both  these types of optical telescopes are still in use.
Radio Astronomy- it came in to being in the most unexpexted manner. In 1931, Karl Jansky, an US radio engineer working with Bell Laboratory, noticed a steady stream of radiation coming in from outer space. It also attracted the attention of an amateur radio operator in the US, Grote Reber, worked single, handed for ten years, studying the sky and analysing radiations. In 1937, he built the world’s first Radio Telescope-a 31 feet 5 inches parabolic dish- and set it up in his backyard at the Wheaton Illinois. In 1940 he produced a radio map of the sky, the first, of its kind in the world. Thus a new branch of astronomy was opened, known as Radio Astronomy.
Ultraviolet Astronomy- it is confined to wavelengths between 912A and about 3000 A. The first successful observation in the ultraviolet region of the spectrum was made in 1946 when the Naval Research Laboratory, USA, flew a captured German V-2 rocket. The first successful detection of far ultraviolet radiation outside the solar system was also made by the same laboratory in 1955 with the help of an AEROBEE 25 rocket. Ultraviolet Astronomy is especially useful in very cases where other techniques have failed to bring in any worthwhile information. Thus there are many young massive stars with effective surface temperature of 10,000 K which emit mostly in the ultraviolet region. These stars can be properly studied by Ultraviolet Astronomy only.
Gamma Ray Astronomy-Gamma rays have the shortest wavelengths and are the most energetic rays so far known. Because of their great penetrating power, they are not absorbed by the interstellar matter and therefore reach us almost unchanged from all parts of the Universe. Gamma Ray Astronomy was born in 1968 with the discovery of very hard gamma ray radiation from the central region of our galaxy by a team of scientists in USA.
Infrared Astronomy- it is important because it enables us to observe objects at temperatures between 10K and 2,000K whether they are cool stars or dust cloud. In the solar spectrum the region nearest to the visible red is called ‘near infrared’. A portion of this near infrared can be detected with special photographic plates. Hence this part of the infrared is called the ‘Photographic Infrared’. Higher wavelengths can be detected by other methods.
Radar Astronomy-it was born in 1940, when a Hungarian Physicist Zoltan Bay sent out a beam of micro waves to the moon and detected the return echo. The basic principle is simple. Short pulses of high frequency radio energy are aimed at a target, from which the pulses are reflected to the earth, where they are picked by sensitive antenna receiver system. The time between the transmission and reception of radar pulses can be converted into a measure of distance by the speed at which these radar pulses travel. Since micro waves can be considered a part of the electro magnetic spectrum, the Radar Astronomy is really a part of Radio Astronomy.

What are Springs?


A place where water naturally flows to the surface is called a Spring. Springs differ between themselves by the conditions of natural underground water discharge depending on such factors as the nature of the water- bearing rocks (porous or fractured), the exposure of the river or gulley slope, the mode of occurrence of the rocks etc. Sometimes, springs emerge at the sea floor and are called ‘Submarine Springs’. 

Springs fed by ground waters are called Gravity Springs, and htose fed by pressure waters are called Ascension Springs. Springs fed by vadose water are subjected to the greatest fluctuations, to the point of complete disappearance at certain times. Most constant are gravity springs fed by ground waters, even though their flow and properties also vary depending upon seasonal changes in the hydrometeorological conditions.
Ascension springs are the natural places of discharge of pressure waters. Typically they are distinguished by more or less constant regime, i.e. head of pressure, flow, chemical composition, temperature etc. they are usually confined to the discharge areas of artesian basins and are often associated with tectonic fault zones.
A springthat breaks out at or near the foot of an escarpment, especially where chalks lie on clay or limestone and sand stone lie on clay.
Vauclusian Spring- the resurgence of reappearance of an underground stream, called after the Fontaine de vaucluse in the lower Rhone valley. It occurs commonly in the limestone country, where water wears subterranean ramifications, finally issuing from the limestone at its base.

Metals and its Types


There are two types of elements – metals and non-metals. About 80 per cent of known elements are metals. Elements which are hard, ductile, brittle and malleable; possess luster and conduct heat and electricity are termed metals. All metals are solids, except mercury and gallium which are liquids at room temperature.
Metals usually have high melting and boiling points.
Chemical nature of metals –Usually metals have the tendency to lose electrons and while reacting with acids, usually replace hydrogen in dilute non-oxidising acids like hydrochloric acid (HCl) and sulphuric acid (H2SO4). Exceptions are copper, silver and gold. Chlorides of metals are true salts and oxides of metals are usually basic. Hydrides of metals are ionic, unstable and reactive.
Although all the metals are reactive, i.e. they are acted upon by common reagents like oxygen (air), hydrogen, halogens, sulphur, water, acids, etc. the extent of reaction is different in the case of each metal. Only gold, platinum and silver, are not affected by air and water under ordinary conditions, and are known as free metals. Various compounds of metals called minerals are found in nature and can be mined. The minerals from which metals can be extracted economically is called ore and the process of extraction of metals from their ores is called metallurgy, which involves:
Calcination – The process of heating the concentrated ore in the absence of air.
Roasting – The process of heating the ore in excess air.
Smelting – The process by which roasted ore is mixed with coke and heated in a furnace to obtain free metal.
Steel and iron –Steel is a form of iron. To make steel from iron, the carbon content is brought down from 5% to 0.5-1.5%.
Heat Treatment of Steel
Quenching – If steel is heated to bright redness and then suddenly cooled in water or oil it becomes extraordinarily hard and brittle.
Tempering – By controlled heating (250-325°C) of quenched steel, its brittleness can be removed without affecting its hardness.
Annealing – If steel is heated to a temperature well below red hot and then cooled turns it soft and the process is called annealing.
Rusting of iron – Majority of metals occur in nature in the combined form and are extracted from their ores. When these metals are exposed to atmospheric conditions they have a tendency to return to their original form. This change is called corrosion of metals and in the case of iron it is known as rusting.
Rusting consists of the formation of hydrated ferric oxide. For rusting water and oxygen are essential-in the absence of water or electrolyte rusting does not occur. The process involves addition of hydrogen and oxygen elements and it is found that mass of an iron rod increases by rusting. Rusting is prevented by coating the surface of iron with metals or non-metals, or by alloying. The coating of another metal is known as electroplating or hot dipping. In electroplating chromium or nickel is used. When a coat of zinc is applied on an iron surface by the hot-dipping process, it is known as galvanizing.
Non-metals – Non-metals are electro-negative elements which have a tendency to gain one or more electrons to form negative ions called anions. All non-metals generally exist as powders or gases, except bromine which is liquid under normal conditions. Non-metals are non-lustrous and are bad conductors of heat and electricity. They cannot be hammered into sheets or drawn into wires like metals. The melting point of non-metals is lower than that of metals.
Alloys – Alloys are homogeneous mixtures of two or more metals and non metals and have more commercial utility than some of the constituent elements. Some of the commercially important alloys are – Magnalium, Duralumin, Aluminium, Bronze, Brass, Tungsten steel.
Minerals – Minerals are naturally occurring chemical compounds of fixed composition and characteristics, physical form and properties. A few minerals consist of only one element. Example graphite and diamond (both forms of carbon), sulphur and gold.
Most minerals, however, are a combination of two or more elements as in halite or rock salt (NaCl). The most common group of minerals are: Silicates, oxides, sulphides, halides, carbonates.Minerals are of two types, viz: metallic or ore, and non-metallic, e.g. carbon, sulphur, etc.

What is an Acid?


Acid – A wide range of  our-tasting chemical substances, the aqueous solution of which is capable of – turning blue litmus red; dissolving certain metals to form salts; reacting with bases or alkalies to form salt and gives hydrogen (H+) ions. An acid consists of two parts of hydrogen H2 and an acid radical .e.g. in Nitric acid, HNO3, the radical is NO3 and hydrogen H2 .The most popular acids are the inorganic or mineral acids, e.g.
Sulphuric acid H2SO4
Hydrochloric acid HCL
Nitric acid HNO3
Phosphoric acid H3PO4
These are classed as strong acids.