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:
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B. If there were no greenhouse effect, liquid water would not exist on the surface of the Earth
D. The Earth has reached thermal equilibrium, emitting the same amount of energy into space as it absorbs from the Sun.
E. The more carbon dioxide there is in an atmosphere, the stronger the greenhouse effect will be
Explanation:
The greenhouse effect plays major role in the climate of our planet in diverse ways:
- it is responsible for the existence of liquid water on the surface of the earth.
- it allows the earth to reach an equilibrium with space in exchange of thermal energy.
- carbon dioxide concentration in the atmosphere has huge roles.
The greenhouse effects results from the abundance of greenhouse gases in the atmosphere. These gases are able to prevent long wave solar radiation from leaving the surface of the earth. When the gases interacts with the radiation, it produces heat that warms the earth surface. Examples of these gases are carbon dioxide, methane, water vapor e.t.c.
The warming of the surface helps to free freshwater trapped as ice and keeps it in the liquid form throughout.
In this exchange of energy, there is a balance between the amount of heat absorbed and radiated back into the atmosphere. As energy enters the earth, it is also radiated out into space. This helps to keep the earth temperature in balance.
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<span>Valence is defined as number of electrons that are present in the outermost orbital. Oxygen is in the 16th column of the periodic table and the total number of valance electrons is determined by units place digit of the column position which is 6 for oxygen. The outermost orbital is the high energy level and there are two in that orbit. So the valance is +2.</span>
So you can make the world greener
Answer:
The vascular system
Explanation:
The human blood circularitory system can be used to explain capillary action in the human body, our heart pumps blood in and out with no use of external forces.
