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Main sequence stars fuse hydrogen atoms to form helium atoms in their cores. About 90 percent of the stars in the universe, including the sun, are main sequence stars. These stars can range from about a tenth of the mass of the sun to up to 200 times as massive.
Stars start their lives as clouds of dust and gas. Gravity draws these clouds together. A small protostar forms, powered by the collapsing material. Protostars often form in densely packed clouds of gas and can be challenging to detect.
"Nature doesn't form stars in isolation," Mark Morris, of the University of California at Los Angeles (UCLS), said in a statement. "It forms them in clusters, out of natal clouds that collapse under their own gravity."
Smaller bodies — with less than 0.08 the sun's mass — cannot reach the stage of nuclear fusion at their core. Instead, they become brown dwarfs, stars that never ignite. But if the body has sufficient mass, the collapsing gas and dust burns hotter, eventually reaching temperatures sufficient to fuse hydrogen into helium. The star turns on and becomes a main sequence star, powered by hydrogen fusion. Fusion produces an outward pressure that balances with the inward pressure caused by gravity, stabilizing the star.
How long a main sequence star lives depends on how massive it is. A higher-mass star may have more material, but it burns through it faster due to higher core temperatures caused by greater gravitational forces. While the sun will spend about 10 billion years on the main sequence, a star 10 times as massive will stick around for only 20 million years. A red dwarf, which is half as massive as the sun, can last 80 to 100 billion years, which is far longer than the universe's age of 13.8 billion years. (This long lifetime is one reason red dwarfs are considered to be good sources for planets hosting life, because they are stable for such a long time.)
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Serotonin is an important chemical and neurotransmitter in the human body. it is believed to help regulate mood and social behavior, appetite and digestion, sleep, and memory
1 - They all are solids due to the strong electrostatic force
<span>2 - They also have high m.p and b.p. </span>
<span>3 - It conduct electricity in molten state or in aqueous solutions </span>
Prokaryotes are unicellular (single-celled) organisms and on the other hand Eukaryotes are multicellular organisms and more developed in organ and structure compared to prokaryotes. Gene regulation is key to both organisms as it determines growth and development and other process and activities performed by the organism. However, the two organisms differ in the way they regulate their genes. Prokaryotes cells lack nucleus while the eukaryotic cells have a well defined nucleus. In Prokaryotes RNA transcription and protein formation occur almost simultaneously while in the Eukaryotes RNA transcription occur before the protein formation in the nucleus and then protein formation occurs in the cytoplasm. In addition both organisms uses the same processes in gene regulation and only differ in the manner the processes are undertaken. Lastly, gene expression in prokaryotes is regulated at transcriptional level whereas in eukaryotes regulation is at many levels.
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