Sciencedaily reported that NASA’s Chandra X-ray Observatory has observed an unusual galaxy cluster that contains a bright core of relatively cool gas surrounding a quasar called 3C 186. This is the most distant such object yet observed, and could provide insight into the triggering of quasars and the growth of galaxy clusters.
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Limestone is an organic, sedimentary rock.It was formed from the remains of tiny shells and micro-skeletons deposited on the sea bed. They were compressed to form solid rock. Limestone is made up of calcium carbonate and reacts with diluted hydrochloric acid. Limestone is formed in layers – called bedding planes. These bedding planes contain vertical cracks called joints. Joints and bedding planes make the rock permeable.
Weathering of Limestone
Weathering is the breakdown of rock by physical, chemical or biological processes. Limestone areas are weathered when rainwater, which contains a weak carbonic acid, reacts with limestone. When it rains limestone is dissolved. Rainwater erodes the joints and bedding planes. In doing this Karst scenery is created.
Karst scenery includes:
Swallow hole – An exposed limestone joint down which a surface river ‘disappears’.
Clints and grykes – Rainwater flowing over an impermeable surface will, on reaching (permeable) limestone, be able to dissolve the joints into grooves called grykes, leaving blocks or clumps of limestone in between called clints.
Stalactite – Water dripping from the roofs of caves leave behind microscopic particles of calcium carbonate. These build up as icicle shaped stalactites.
Stalagmite – Drips splashing onto the floor of caves leave behind microscopic particles of calcium carbonate. These build up on the floor of caves.
Limestone and recreation
Limestone areas are popular due to the range of leisure activities that people can participate in. These include walking, pot holing, climbing and abseiling.
Source:http://www.geography.learnontheinternet.co.uk/topics/limestoneinfo.html#lime
Further Readings
The research, led by scientists at the National Center for Atmospheric Research (NCAR) in Boulder, Colo., uses observations, gene expression studies, and computer modeling to show that deciduous plants absorb about a third more of a common class of air-polluting chemicals than previously thought.
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Jugnu, the nano satellite developed by Indian Institute of Technology-Kanpur (IIT-K) is expected to be launched in the polar orbit from Satish Dhawan Space Centre at Sriharikota in the first six months of 2011.
Though it was expected that it would be launched this month, the Indian Space Research Organisation (ISRO) has allotted a slot in the first half of 2011 to IIT-K for the launch.
The final model of the satellite is being given the final touches. A team of 12 professors and 45 students have been working on the project since December 2007.
Weighing 3.5 kgs, Jugnu will be launched in the Polar orbit, 700 km above the ground level. The nano satellite, which has a life span of a year, will encircle earth 14 to 15 times each day and transmit images of weather, soil and water bodies to the IIT-K base station.
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Source:Indian Express
In the satellite industry, ‘small’ could be the next big thing in the coming years
