Star is a brilliantly glowing sphere of hot gas whose energyis produced by an internalnuclear fusion process. Stars are contained in galaxies. A galaxy contains not only stars, but clouds of gas and dust. These clouds are callednebulae, and it is in a nebula where stars are born. In the nebula is hydrogen gas which is pulled together by gravityand starts to spin faster. Over millions of years, more hydrogen gas is pulled into the spinning cloud. The collisions which occur between the hydrogen atoms starts to heat the gas in the cloud. Once the temperature reaches 15,000,000 degrees Celsius, nuclear fusion takes place in the center, or core, of the cloud. The tremendous heat given off by the nuclear fusion process causes the gas to glow creating a protostar. This is the first step in the evolution of a star. The glowing protostar continues to accumulate mass. The amount of mass it can accumulate is determined by the amount ofmatter available in the nebula. Once its mass is stabilized, the star is known as a main sequence star. The new star will continue to glow for millions or even billions of years. As it glows, hydrogen is converted into helium in the core by nuclear fusion. The core starts to become unstable and it starts to contract. The outer shell of the star, which is still mostly hydrogen, starts to expand. As it expands, it cools and starts to glow red. The star has now reached the red giant phase. It is red because it is cooler than the protostar phase and it is a giant because the outer shell has expanded outward. All stars evolve the same way up to the red giant phase. The amount of mass a star has determines which of the following life cycle paths the star will take.
Answer: White Oak
White oak comprises 15% of the commercially available hardwoods in the US. It is a used for structural timbers, flooring, and furniture because<span> of its length (rees average approximately 70 to 80 feet in height), color (White with creamy sapwood and dark gray-brown heartwood) and texture (very strong and hard, and with good steam bending properties). It takes a good finish when machined, nailed and screwed well. </span>
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Nucleus is the control centre of the cell and manages all the cellular activities taking place inside the cell. It consists of four parts :-
- Nuclear membrane,
- Nucleoplasm,
- Chromatin material and
- Nucleolus.
The Chromatin material(Condensed - Chromosome) stores the cell's DNA which is transmitted to next generation.
