The Shiny Shimmering Splendid Star

The Shiny Shimmering Splendid Star

Every summer, when we go to the provinces, my family always caught me during the nights staring into the void, but I’m actually staring at the sky because I sincerely enjoy the dandruff-ish look of stars in the provinces (because they had less light pollution).

When I first got my DSLR camera (Nikon D3100) last year, I had an intense feeling of thirst for information on how I can use my camera more than just the technical stuffs. So I began searching the net about everything – on how to do Bokehs to Light painting – until I read an article about Star trailing. This effect really fascinates me.

It says that your camera must have a remote, so I went to camera shops to inquire but they said my camera doesn’t have its built-in ability to sense the signals from the remote, which ends one of my dreams shattered, unless  if I’ll have another camera.

So I would like to dedicate this post to my broken ambition.

Why do the stars shine?

The reason why stars shine is that there is an internal process going on within each star. Stars initially form from large balls of gas, typically a cloud of cold molecular hydrogen that collapses and breaks into fragments and pieces. As held together by gravity, stars are continuously crushing themselves inward, resulting to causing heat to be produced due to friction of the gravitational energy that goes into the motion of the gas. With the intense pressure and increasing temperature, a nuclear fusion reaction takes place. As it contracts, its temperature rises.  When the heat gets high enough, it causes the individual the hydrogen nuclei in the plasma inside the core of the star to collide. As soon as enough protons can collide into each other with enough speed, they stick together to form a helium nucleus; which generates a tremendous amount of energy at the same time. This conversion of hydrogen into helium is the first reaction that happens in every star, it is called the main sequence. The stellar gas, now in a spherical shape, is contracted further by gravity while exploding by fusion. Together, a balance is reached and a star is born.

The reaction actually ends up with a surplus of energy according to the equation E=mc2. In a star, four hydrogen-2 atoms form into a helium-3 atom; and according to E=mc2, releases a lepton and photon, which is then turned into energy. This is because the mass of the combing hydrogen is greater than the end product of helium. Therefore, the mass is converted to energy, and that energy is the electromagnetic radiation (light).

The tremendous amount of energy released in the star’s center traverses the star’s interior to the surface. Once it has reached the surface, they become visible light photons which are radiated into space as light, heat x-rays, ultraviolet light and radio waves in the form of gamma rays. The star then shines after the process of nuclear fusion has successfully occurred out in space. These gamma rays are trapped inside the star, and they push outward against the gravitational contraction of the star. That’s why stars hold to a certain size, and don’t continue contracting. The gamma rays jump around in the star, trying to get out. They’re absorbed by one atom, and then emitted again. This can happen many times a second, and a single photon can take 100,000 years to get from the core of the star to its surface.

The photons leap off the surface of a star, lost some of their energy, become visible light photons, and not the gamma rays they started out as; and head out in a straight line into space. They can travel forever if they don’t run into anything. When the core hydrogen finally runs out, the star will temporarily spike in brightness by up to a thousand times its current luminosity, expand, and cool at the surface.

Nuclear Fusion Process

Nuclear fusion is the process by which two or more atomic nuclei join together, or “fuse”, to form a different single heavier nucleus. During this process, matter is not conserved because some of the mass of the fusing nuclei is converted to energy which is released. The binding energy of the resulting nucleus is greater than the binding energy of each of the nuclei that fused to produce it.

The fusion of two nuclei with lower masses than iron (which, along with nickel, has the largest binding energy per nucleon) generally releases enormous energy, while the fusion of nuclei heavier than iron absorbs energy. This process gives off a lot of energy that we can see as light.

Luminosity

Luminosity is generally understood as a measurement of brightness.

In astronomy, luminosity measures the total amount of energy emitted by a star or other astronomical object in joules per second, which are watts. A watt is one unit of power, and so just as a light bulb is measured in watts. Luminosity is the amount of electromagnetic energy a body radiates per unit of time. It is measured in two forms: apparent (visible light only) and bolometric (total radiant energy).

A star also radiates neutrinos, which carry off some energy, about 2 % in case of our Sun, producing a stellar wind and contributing to the star’s total luminosity.

The observed brightness of a star is called its apparent magnitude, because without measuring the star’s distance, we do not know how much light it emits. When we do measure a star’s distance, we can make a measurement of the star’s true energy output. The total energy output of a star is called its luminosity. There are a variety of units of luminosity, but one way to measure luminosity is in Watts. The luminosity of a star is an astronomical quantity, for example the Sun has a luminosity of about 1026 Watts. Since this is another case of large numbers, we often measure the luminosity of other stars in terms of how bright or dim they are compared to the Sun. For example, a star that emits 1027 Watts is 10X more luminous than the Sun, and we say it has 10 solar luminosities. A star that emits 1025 Watts is 1/10th as luminous as the Sun, so we say that it has a luminosity of 0.1 solar luminosities.

Facts about stars

  • All stars are hot balls of glowing plasma held together by their own gravity.
  • Eventually, a star will use up all of its available small atoms, and the fusion energy is no longer available.  In some stars, the further collapse triggers fusion of helium into carbon, or carbon into even heavier elements.  Finally, all the elements that can provide energy are exhausted, and the star starts its final collapse.
  • Every second, a star like the Sun converts 4 million tons of its material into heat and light through the process of nuclear fusion.
  • If the star is big enough to start with, the central temperature will be high enough to really keep that fusion going, and the heat gradually will seep out to the outside parts of the star, so the outer surface regions will also rise to quite high temperatures.
  • It is the temperature of the outer surface that determines the way the stars shine – our sun has an outer temperature of around 5000 degrees, but other stars can be as hot as 50,000 degrees, producing much bluer light, while red dwarf stars are considerably cooler and produce mostly red and infrared light.
  • Luminosity of the sun  =  3.845 X 10**26 watts   =   1367 watts/square meter at Earth
  • The process that causes stars to shine is the same one that we have harnessed for use as a weapon: nuclear fusion.
  • When modern electronic light detectors (using the “photoelectric effect”) were first devised and used to measure the brightnesses of stars, it was found that a first magnitude star produced approximately 100X the electrical current of a sixth magnitude star.
  • All this heating, from both gravity and nuclear fusion, creates a pressure that causes the star to quit contracting at some point.
  • Because stars are so massive, the density and pressure in the cores are extremely high. In fact, the Sun’s core is so hot and has such high pressure that it undergoes nuclear fusion.
  • Fusion is the process that powers active stars.
  • If a star is located about 8 light-years away; you’re seeing photons that left the surface of the star 8 years ago and traveled through space, without running into anything.
  • It is believed that most stars are in the ages of 1 billion to 10 billion years. Its age is highly dependent on its mass, having an indirect relationship. That is, the higher the mass density of the star, the shorter is its life span while stars having lesser mass densities tend to reach hundreds of billions of years. Stars vary in color depending on it mass and temperature. Red is deemed to be the coolest color while blue projects otherwise.
  • One of the first things you notice about stars when you look at the night time sky is that some are brighter than others. In fact, the brightest stars you see are about 200 times brighter than the faintest ones your eye can detect. Astronomers use a specific system to note how bright a star is: the magnitude system.
  • Stars are giant balls of glowing gas. Stars shine because the gas inside them is so hot that a process called “nuclear fusion” takes place.
  • Under increasing compression, the helium created earlier within the nuclear furnace will begin to fuse to carbon and oxygen, causing the future star to dim back some to become a modest red giant star like so many of those that populate the naked-eye sky. When the helium is gone, the Sun will brighten even more, to some 5000 times its present luminosity, expand to nearly the size of Earth’s orbit, and become even cooler and redder. Then it will slough off its outer hydrogen layers, exposing the core. The core in turn will illuminate the expanding debris to briefly create a planetary nebula and will then die and cool as an ultradense, dimming carbon-oxygen white dwarf with somewhat over half its current mass
  • We know that stars are constantly emitting photons in all directions. The photons carry energy with them. The rate at which photons carry away energy from the star is called the star’s luminosity. Luminosity is frequently measured in watts (that is, joules per second).

Myikc Tsoerr, 3AD8

———–Sources———-

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Checked by Prof. Crisencio Paner

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1 Comment (+add yours?)

  1. mestreseo
    Dec 14, 2012 @ 13:39:31

    thanks for taking the time to write, i never find time to write good posts. i really appreciate all the good information everyone has to share. mestreseo mestreseo mestreseo mestreseo mestreseo

    Reply

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