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:
(C)cell nuclei that contain DNA
Explanation:
They are eukaryotic, which means they have a nucleus. Most have mitochondria. They can be parasites. They all prefer aquatic or moist environments.
Answer:
Accumulation flooding occurs because the ground is completely filled with water and there is no longer a zone of dry land.
Explanation:
Flood is the overflow of water on the land which is usually dry throughout the year. It occurs when more water comes in the river due to rainfall or breaking of dam. But mostly flood occurs, due to melting of ice on the poles because of global warming. Global warming refers to the increase in average temperature due to presence of greenhouse gases such as carbondioxode, methane and water vapors etc in the atmosphere.
Answer:
Explanation:
since during cellular respiration the carbon dioxide as well as the oxygen is provided through the food as a product of cellular respiration. therefore, energy from the food will be used after it leaves the mitochondrion during cellular respiration, through this the damage cell is repaired through cellular respiration.
Answer:
D
Explanation:
Alternative energy is best defined as the use of energy sources other than traditional fossil fuels, which are considered environmentally harmful and are in short supply. Fossil fuels consist of natural gas, coal, and oil. Currently, fossil fuels are the most used energy source to heat our homes and power our cars.
