The information contained in this paper will explain the science of the stars. Other information in this paper will be a description of how astronomical instruments aid astronomers in determining the rotation rate of distant objects, speed, temperature, and composition. Also, the author will provide an explanation of the properties of stars in the Hertzsprung – Russell diagram. In conclusion, the complete lifecycle of the Sun will be explained, along with a determination of where the Sun is in its lifecycle.
Science of Stars
What is a star?
A star is defined as “a gaseous mass in space that generates energy by thermonuclear reactions”. Our sun is a star and its primary composition, as well as that of all the other stars, is helium and nitrogen gas, a stars core is hot and dense, within the core, the temperatures’ are extremely hot this is where atoms move so quickly that they will stick to other atoms when they collide with them, this forms larger atoms and releases a vast amount of energy. This is the process of nuclear fusion. Stars vary in size from being equal to the diameter of a planet, all the way to being larger than the diameter of the whole earth’s orbit. The histories of the stars in the galaxies are traced through the age, compensation, distribution, and the dynamics and evolution of that galaxy. As fundamental building blocks of the universe, Stars play a vital role in the planetary systems that coalesce around them by manufacturing and distributing heavy elements such as carbon, nitrogen, and oxygen. The C-N-O families of elements are the raw materials for planet formation. “We have learned that the lightest chemical elements were synthesized in the Big Bang, but that the heavier elements were made in stars. When the more massive stars exploded as supernovae, they enriched the
material out of which subsequent generations of stars would be made with an ever-increasing amount of these heavy elements”(Origins of Science Road Map,2000).
When exploring how astronomical instruments help astronomers determine the rotation rate of distant objects, speed, temperature, and composition, it is interesting to note that astronomical instruments are divided into two groups. The first group is made up of all the instruments that are used for observing celestial objects, such as the telescope, which is enables objects invisible to the naked eye to be seen and photographed. The first group is the group of instruments that astronomers use to help astronomers determine the rotation rate of distant objects, speed, temperature, and composition. One example of this instrument is the James Webb space telescope. Through the use of this telescope and others, astronomers have the ability to study light from distant objects’ and determine the rotation rate of distant objects, speed, temperature. This process is called spectroscopy. “Spectroscopy pertains to the dispersion of an object’s light into its component colors (i.e. energies). By performing this dissection and analysis of an object’s light, astronomers can infer the physical properties of that object such as temperature, mass, luminosity and composition”(Kulesa,1997). Spectroscopy was first used to study celestial objects in 1863 by William Higgins. It was discovered by using this technique that different objects give off and absorb different spectrums of light. Where the object falls in the spectrum of light can be determined by examining its peak intensity at each wave length of light. There are three types of spectra used to evaluate light. These types of spectra are Emission spectra, continuum spectrum, and absorption spectrum. Stars brightness is determined by its luminosity and its distance from earth .One star can have a level of brightness that differs from others as there are many variables that can have an effect on the brightness of a star. Some of these factors include the temperature, the hotter the star is, the more luminous it appears to be, and the density of the star is also a contributing factor as well as the distance from our planet. All stars are unique in that they all
contain these variables that cause them to appear brighter or dimmer. The two major factors are distance and “Star Power”. If the star being observed by the naked eye appears to be brighter it may appear that way because it is closer or larger than the other stars around it, stars do have different brightness levels than other stars.
The Hertzsprung – Russell diagram
The Hertzsprung – Russell diagram was developed when Danish astronomer Ejnar Hertzsprung and American astronomer Henry Noris Russell recognized the relationship between stars luminosity and its surface temperature. This relationship was used by the two astronomers to develop a type of graph to identify where each star is in its lifecycle. The properties of stars in the Hertzsprung – Russell diagram are its luminosity and temperature. A star’s luminosity or amount of energy radiating from it is plotted on the y-axis or vertically and usually based on a ratio-scale with the reference point being the Sun. A star’s surface temperature, known as its spectral type, is plotted on the x-axis or horizontally. By graphing these two properties of stars we are able to map out where most stars are in their lifecycle. Reading an H-R diagram: a star in the left upper corner would be bright and hot. “A star in the right upper corner would be bright and cool. The sun rests approximately in the middle of the diagram and it is the star which we use for comparison” (Kroswell, 2012). A star in the lower left corner of the diagram would be hot and dim. A star in the lower right corner would be cold and dim.
Lifecycle of the Sun
Approximately 4.75 billion years ago, a star was born. This star which is our sun was created with an immense gas cloud and particles comprised mostly of hydrogen, when this large gas cloud and dust cooled down, it contracted because of the gravitational pull between the particles the cloud is comprised of. This constant contraction created tons of pressure on the center of the sun which is the core; the electrons that were attached to the neutral gases were stripped off, causing the gas to become charged. The
hydrogen nuclei which were positively charged in the core collided with one another with such brute force they fused together. This nuclear fusion process resulted in the formation of helium. The nuclear fusions release of energy prevented the star from further collapse. When nuclear fusion occurred, the gas cloud became a star. This star is the Sun (Villanueva, 2010). As the sun grows older, it will continue to expand. “As the core of the sun runs out of helium and hydrogen, its core will contract and the outer layers cool, expand and become dimmer. The sun then becomes a red giant” (Col, 2010). As the external territories grow in size, the helium nuclei in the core continue to fuse into carbon, eventually, the carbon will no longer fuse any further. Consequently the core will balance and the remaining outer provinces will continue with their progression that enables it to ultimately be removed. The core will then be a white dwarf, and the external regions will be planetary nebula. Conclusively, this white dwarf will discharge all of its residual heat, and will developing into a dark cold mass or a black dwarf (Villanueva, 2010).
Where the Sun is in its Lifecycle
The suns entire lifecycle is made up of the following stages: protostar, main sequence, red giant, and lastly a white dwarf. Currently, the age of the Sun is approximately 5 billion years; this puts the sun halfway through its lifecycle. Dating of the formation of the solar system is done in two ways: the sun’s main sequence age, which is determined through the use computer models of nucleocosmochronology and stellar evolution, is believed to be equal to the amount of years the sun was formed. Currently, sun is approximately halfway through the main-sequence evolution, (when nuclear fusion reactions in the suns core fuse hydrogen into helium. Every second, four million tons of matter is converted into energy in the sun’s core, producing solar radiation and neutrinos; at this speed, the sun will have converted one hundred earth-sized masses of matter into energy. The total amount of time that the sun will spend as a main star sequence is approximately ten billion years.
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