This MLA essay briefly examines the nature of stars as celestial bodies and their place in the universe. This sample essay was written at the undergraduate level to serve as a sample for the Ultius blog.
The Stuff of Stars
“Be humble, for you are made of earth. Be noble, for you are made of stars.” -Serbian proverb
Philosophers and poets throughout the ages have claimed and now scientists agree that everything is made of star dust. But what is a star, exactly? They shine both day and night as the sun, close to home, and constellations across the sky. They represent the 50 states on the American flag and are synonymous with a person of great fame and popularity. However, despite their ubiquity, their true nature is discussed very rarely. In this essay, the origin, role, and lifecycle of stars will be discussed.
Overview of stars
- The Sun that orbits planet Earth is a G2 yellow dwarf star. This is the most common star type on the spectrum (Space facts).
- Stars work through nuclear fusion, a process involving the breaking down and rebuilding of atoms to destroy and create new elements on the periodic table of elements (Space facts).
- The closest star to this solar system is Proxima Centauri at 4.2 light years away meaning that, even when seen by inhabitants of Earth, the light of the nearest star in the sky was emitted over 4 years ago (Space Facts).
- The Milky Way contains 200-400 billion stars which is about 40 times the number of human beings on Earth (Space Facts).
- The total number of stars in the known universe is estimated to be between 70 and 300 sextillion. A sextillion is a number with 23 zeros after it (Space Facts).
- The planet and all its inhabitants are, according to astrophysicist Carl Sagan, made of star stuff (Mellina).
A star is born
To grasp the nature of a star, one must begin with the actual beginning of everything. Before the Big Bang, the universe was as an infinitesimal speck of unimaginably dense, hot matter, When the universe was roughly the age of 10 to the power of negative-thirty-four, that single speck exploded, hurtling cosmic debris faster than the speed of light. The universe doubled in size nearly 90 times almost instantly from subatomic particle size to the dimension of a golf-ball (Choi A). According to NASA, matter as we know it began to exist only as the universe cooled after this explosion. At 1 second, the universe was loaded with neutrons, protons, photons, neutrinos, and anti-electrons (Choi A). At three minutes, the first light elements were created by a process called nucleosynthesis. The temperature fell from 100 nonillion, Kelvin to 1 billion Kelvin. The protons and neutrons combined to make deuterium, hydrogen’s isotope, helium, and lithium (Choi A). The first of the elements that we now recognized had been born.
This scene continued in darkness for about 380,000 years because the universe was far too hot for light to shine in (Choi A). The first rays of light began only after the cooling process had progressed to the point where the atoms and elements that had formed could slow down enough to condense into a plasma soup of protons, neutrons, and electrons. This energy fog eventually collapsed and collided in on itself, making electrically neutral and transparent gas, a field through which rippled the first flashes of light. These flashes are known as cosmic background radiation, the ancient silhouette of the first stars (Choi A). This light rippled through the next 400 million years, increasing in frequency as the gas grew cooler and denser. This was known as the cosmic dark ages because there was very little order, but it was also the very beginning of the universe’s galaxies. These infant stars emitted the most energetic ultraviolet light which in turn ionized and destroyed most of the neutral hydrogen particles in the universe(Choi A).
Today, scientists have identified of the place and color of some of these early stars. Astronomers with the NASA Hubble and Spitzer space telescope have managed to locate the MACS0647-JD Galaxy, a star system nearly 13.3 billion light years away which makes its birth about 400 million years after the Universe was created (Moskowitz). Far smaller than Earth’s Milky Way, this distant galaxy is tiny at less than 600 light-years wide and very red, compared to the yellow light we know in the Milky Way (Moskowitz). It is likely that this first galaxy set off several cosmic events which led to the formation of the younger galaxies around it, including our own. If astronomers were to draw a genealogy of stars, MACS064-JD would be the oldest star system in the tree, acting as a sort of intergalactic matriarch.
The Milky Way forms
The Milky Way galaxy, while much larger than this progenitor galaxy, only came into existence about 10 billion years ago. Our home galaxy was born as a froth of heated plasma plunged in on itself and set off a not-so-Big Bang. This explosion scattered star seeds at roughly 40 times faster than the rate of expansion observed at present (Weaver). Although there is much speculated and some small amount known about the Milky Way, far more is unknown as astronomers from Earth work within the limited perspective afforded to them as stranded citizens in the Milky Way’s 15,000 light year wide disc (Weaver). According to NASA, “Astronomers don’t have baby pictures of our Milky Way’s formative years to trace the history of stellar growth so they studied galaxies similar in mass to our Milky Way, found in deep surveys of the universe” (Weaver).
Astronomers have built a system of understanding from their space- and ground-based telescopes, coupled with the most advanced scientific theories regarding stellar genesis to comprehend the Milky Way. All that serious hard work aside, if an astronomer or planetarium guide shows you a picture of the Milky Way, keep in mind that it is an extrapolation, not a literal picture since no space craft or satellite has traveled outside our galaxy.
However, our sun, the Earth and our solar system’s central power source, can very much be directly and literally observed. The sun came into existence around 5 billion years ago, near the end of the Milky Way’s star birthing phase. The late start means that our solar system contained the rare and heavy elements that were necessary to create the planets we call neighbors and, more importantly, the life-bearing planet Earth. (Weaver).
Our sun, like all stars, is driven by nuclear reactions. The visible aspect of the sun is 10,000 degrees Fahrenheit or 5,500 degrees Celsius, a temperature that happens to be just right thanks to the exact orbit of the Earth (Choi B). Were it any closer or farther away, the oceans would either boil or freeze, completely precluding any chance of life. Since the Earth has a precise proximity to the sun, the only major sun-related risk posed to Earth is the sun’s own death. According to estimates made from the observation of other stars a yellow dwarf star will eventually expand into red dwarf star that is 0.08 to 0.6 times as massive as the sun is presently (Gregersen). At this time, the Earth will either be burned to a cinder unless it is protected or moved by some currently unknown natural or man-made efforts.
The sun’s future as a red dwarf star is explained by nuclear fusion. Nuclear fusion is the primary way by which stars generate light, heat, and new elements that in turn give the galaxies their shape, luminosity, and warmth. This occurs as the star’s hydrogen is consumed and its other elements collapse on themselves due to the pull and mass of the star’s own inner gravity. This process occurs through the proton-proton chain, each iteration of which takes hundreds of years to complete (Impey).
The fusion process in this case involves a hydrogen-1 atom plus a hydrogen-1 atom to make a hydrogen-2 molecule with an additional electron and neutron. The hydrogen-2 combines with another hydrogen-1 to make helium-3 with a proton. Finally, helium 3 is combined with another helium-3 to make helium-4 with a hydrogen-1, another hydrogen-1, and a proton (Impey). In heavier stars, such as blue giants, the process goes to higher levels where elements of a higher number are combined with each other to create even more complex elements (Impey). The finding goes that a single beam of light may actually be 1012 years old as it leaves the sun making each strand a veritable piece of ancient history (Impey).
Planet Earth is a fortunate rock orbiting a typical star of color and light in the Milky Way galaxy. Stars are both the engine and the fuel that drives the universe as we know it, giving light and warmth, but also generating the elements that form the world around us. Though they won’t last forever, the scale of time from birth to death for stars is so vast that humanity barely has numbers to describe it. In all of human knowledge, we will be fortunate to decode even a small portion of what makes stars tick and every little revelation will be a tremendous step forward in understanding our universe.
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Choi, Charles Q, B. Earth’s Sun: Facts About the Sun’s Age Size and History. Space.com, 2014. Web. July 23, 2016. http://www.space.com/58-the-sun-formation-facts-and-characteristics.html.
Crowley, Aleister. Liber vel Legis. Thelema 101, n.d. Web. July 21, 2016. http://www.thelema101.com/liber-al.
Impey, Chis. Nuclear Reactions in Main Sequence Stars. Teach Astronomy, 2012. Web. July 23, 2016. http://m.teachastronomy.com/astropedia/article/Nuclear-Reactions-in-Main-Sequence-Stars.
Moskowitz, Clara. Farthest Known Galaxy in the Universe Discovered. Space.com, 2012. Web. July 23, 2016. http://www.space.com/18502-farthest-galaxy-discovery-hubble-photos.html
Smith, Rene. Space Facts, Science Kids, 2007. Web. July 22, 2016. http://www.sciencekids.co.nz/sciencefacts/space/stars.html.
Weaver, Donna. Our Sun Came Late to the Milky Way’s Star-Birth Party. NASA.Gov, 2015. http://www.nasa.gov/content/goddard/our-sun-came-late-to-the-milky-way-s-star-birth-party.