Answer:
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.)
Explanation:
I hope this helped!
Answer:
Enzymes are involved in the formation and composition of every cell in the body. Thus they also control the working of every organ and even the brain - the control center. They are involved in the breakdown, absorption, distribution and circulation of various nutrients entering the body.
Explanation:
This is determined by its atomic number. The atomic number of an element determines its protons. So for example....
The atomic number of Boron is 5, therefore....the protons are 5.
If the ice is lying on land, melting ice will slowly raise sea levels.
Explanation:
Ice in the Arctic ocean is floating on the ocean and so when it melts it does not raise sea levels anymore - its like ice cubes in a drink - its already displaced as much water as its going to.
However, the big ice caps of Antarctica and Greenland are mostly lying on land and so as they melt they add more water to the oceans and the average sea level rises.
If all the ice in Greenland were to melt the sea level would rise by about 7 meters which would flood out millions of people living in coastal cities. If all the ice in Antarctica were to melt, this would add 72 meters to average sea levels.
Right now, thermal expansion of the oceans, plus melting ice from continental alpine glaciers, is contributing the most to sea level rise (as the atmosphere warms from global warming, some heat is transferred to the oceans). Current estimates are that sea levels may rise as much as 1 meter (3-4 feet) by the year 2100.
