Stars at Night
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People often gaze at the 200,000,000,000,000,000,000,000 stars in the sky with awe and wonder. Well, they actually only gaze at up to 4,500 at any one time due to the limit of how far into space the human eye can see, and that number is likely to dip to as low as 35 for those in the middle of a major city amidst all of the bright city limits that exist there. However, that's more than enough to get the imagination going, wondering how they came to be, what they are like and what will happen to them.

Facts about Stars

  • The majority of stars are classified as main sequence stars. Stars not along the main sequence are considered dwarf stars or giants.
  • Because stars are so massive and have tremendous gravitational fields, they are able to fuel themselves by burning the elements that they are composed of. Smaller stars burn lighter elements such as hydrogen and helium, and larger stars have the capability to burn heavier elements like iron.
  • Currently our sun burns hydrogen as its fuel source. At some point in the future - approximately 5 billion years from now - it will run out of hydrogen to burn in its core, and will leave the main sequence. It will then begin expanding and become a red giant.
  • The closest star to our Sun is called Proxima Centauri. The word "Proxima" in Latin means "near", or "close", and Centauri is the equivalent in Latin for the word "Centaurus" - the constellation in which the star is located in.

How are Stars Formed?

The skies are full of nebulas, which are cold gaseous clouds. As gravity starts to take over, they began to condense into a number of clumps. Nuclear reactions will cause the temperatures there to increase. Once the temperature reaches 18 million degrees Fahrenheit, a new star has begun its life. This entire process generally takes 10 million years although it can be done in as little as 1/100th of that time frame.

To put the amount of space that is necessary to form a star into perspective, consider that a gaseous cloud the size of hundreds of our solar systems would have to exist before it condensed into a star the size of the sun.

Life Cycles of Stars

Once a star is formed, it will turn hydrogen atoms into helium for quite a long time. For example, the sun will be doing that for 10 billion years. Stars that are larger than the sun will tend to die out in a fraction of that time. For example, one that is 10 times the size of the sun will last for 1/500th of that time or 20 million years. This is because the greater gravitational forces in play with a star that much larger end up causing it to burn out at a quicker rate.

Once this period ends, stars become red giants. Surprisingly, when a star is about to die, it will expand many times its size. That is because all of the hydrogen will have been made into helium, and the helium then collapses upon itself, heating up the core and expanding the size of the star to between 100 and 1,000 times its normal size while causing the overall heat that emanates from it to be reduced by half.

Stars that were smaller in their prime will often become a white dwarfs, an extremely dense form of matter. At this stage, it could be 1 percent of its original size with the same mass as before. After tens or hundreds of billions of years, it will eventually cool so much that it becomes a black dwarf. Its temperature will be minimal at this point.

Conversely, a largish star will tend to explode, sending itself out at a speed of about 17,000 miles per second. The earth and our entire solar system is likely made up of supernova remnants from elsewhere. What is left behind will either be a neutron star or black hole, both of which have a significant amount of gravity. The latter is the more extreme of the two with so much denseness that the same ratio would cause the mass of the earth would be the size of a pea.

Famous Stars

The most famous star is our own, the sun.

The second-nearest star to earth is Proxima Centauri. However, it is so relatively dim that it is not one of the 9,000 stars – 4,500 in each hemisphere – that can be viewed with the naked eye. However, it makes up for that in longevity as it burns its fuel in a much more economical manner, meaning that it will last for trillions of years, much longer than the sun's lifespan.

The North Star may be the most famous one other than the sun as people have long looked upon it to tell which way is north, especially before compasses were invented, not to mention more advanced forms of technology and communication. It can be found at the end of the Little Dipper's handle. Another way to find it is to locate the Big Dipper and picture what's in it being flung upwards. The right portion of that will hit the North Star. The reason why it is special is because it is near the center of the sky's axis in the northern hemisphere and it barely moves; it does rotate, but it's a tiny circle.