The Formation of Stars - Essay Example

Essay: Star Formation Table of contents ………………………………………………………………………………….3 Introduction………………………………………………………………………...........4 Star formation…………………………………………………………………………....4 Protostars…………………………………………………………………………….......5 Evolution of T-Tauri star………………………………………………………………...7 Main Sequence stars……………………………………………………………………...8 Stars and their fate………………………………………………………………………..9 Conclusion……………………………………………………………………………….10 References………………………………………………………………………………..11 Abstract Formation of stars is a process through which dense areas inside molecular clouds in stellar nurseries also called star-forming areas collapse leading to formation of stars. Star formation is a branch of astronomy and comprises the study of gigantic molecular clouds(GMC) and interstellar medium as predecessor to the process of star formation and the learning of young stellar objects and protostars as its direct products. Planet formation is another branch of astronomy closely related to star formation. The theory of star formation together with accounting for the formation of one star must also put into account the statistics of initial mass function and binary stars. Key words: Molecular clouds, star formation, astronomy, gigantic molecular clouds (GMC), interstellar medium, initial mass function, binary stars Introduction Some of the widely known astronomical substances that represent mainly the basic building blocks of most galaxies are stars. This therefore means that the composition, age and distribution of stars in a galaxy usually suggest the dynamics, evolution and history of that particular galaxy. Furthermore stars are mostly responsible for the manufacturing and dispensing of heavy elements for instance oxygen, carbon and nitrogen and therefore their distinctiveness is closely tied to the uniqueness of the planetary systems that may possibly unite around them. As a result the study of the origin, life and ultimately death of stars is key to the astronomical field (Whitworth, Thompson, 2012). Star formation Stars usually are formed within comparatively dense concentrations of interstellar dust and gas referred to as molecular clouds. These areas are mostly very cold and temperatures may fall to around 10 to 20K, just over absolute zero. Gases under these temperatures become molecular which means that there is binding together of atoms. Within the interstellar gas clouds are mostly Hydrogen and carbon monoxide molecules .These low temperatures result in extremely cold conditions causing the gases to clump together to high densities. It is when the density attains a specific point when stars are formed. The regions are mostly dense and consequently opaque to any visible light and are referred to by the name dark nebula. They also do not shine by light that is optical which means that they are observed and investigated by use of IR as well as radio telescopes (Whitworth, Thompson, 2012). Formation of stars starts when the denser regions of the cloud’s core collapse due to their own gravity or weight. The cloud’s core usually has got masses to the tune of 104 solar masses and is mostly in the structure of dust and gas. Being of higher density than the outside clouds, the cores collapse being the first ones. As they collapse, the cores fragment into clumps of about 0.1 parsecs in dimension and in masses of around ten to fifty solar masses. It is these clumps that lead to the formation of protostars, with the whole process taking about ten million years. This is known because many of the cloud cores have got IR sources which give evidence of energy that results from collapsing protostars. This is potential that is later converted into kinetic energy. Another piece of evidence is found in young stars that are bordered by gas clouds, which is the dark molecular cloud leftover. These occur in what is known as clusters-which are groups of stars forming from similar cloud core. Protostars The moment a clump breaks free from other regions of cloud’s core, it usually has its own distinct identity and gravity and this is what is known as a protostar. During the formation of protostar, loose gas simultaneously falls into its center. This infalling gas discharges kinetic energy in heat form and the pressure and temperature in the interior of the protostar rises. Thus as its heat draws near thousands of degrees, it is converted into a IR source (Naveed, 2008). During the preliminary collapse, the clump is typically transparent to any radiation and thus the collapsing progresses quite quickly. While the clump becomes denser, it turns opaque. Consequently, trapping of any escaping IR radiation occurs and the pressure and temperature in the middle starts to increase. The pressure later on at some particular point stops the infalling of more gas inside the core and the substance becomes stabilized as a protostar. Initially the protostar has got around 1% of its ultimate mass. However the star’s envelope goes on to develop as infalling substance is accreted (Lee, 2000). Thermonuclear fusion starts in the core of the star once a few million years have elapsed and subsequent production of a tough cosmological wind stopping any further infalling of new mass. This protostar is now taken as a young star because it’s fixed mass and the fact that its potential evolution is now firmly set.3 dimensional models from computers of formation of stars forecasts that the revolving clouds of breaking up dust and gas collapse into 2 or 3 blobs; and this probably would explain the reason why several of the stars within the Milky Way are in clusters of multiple stars or rather paired (Lee, 2000). Collapsing of the cloud leads to formation of a very hot dense core which starts gathering gas and dust. It’s not all this material that ends up becoming part of the star –the remnants turns into asteroids, comets, planets or still may stay behind as dust. There are instances when clouds may not necessarily collapse at a pace that is steady. For instance in January 2004, James McNeil an amateur astronomer found out a tiny nebula that suddenly emerged close to nebula Messier 78, which is in the Orion constellation. After pointing their telescopes at McNeil’s Nebula, observers discovered something exciting-its level of brightness seems to differ. Observations using Chandra X-ray Observatory of NASA gave a possible explanation; the relations between the adjoining gas and the magnetic field of the young star lead to episodic brightness increases (Peter, 2011). The moment a protostar becomes a star that is burning hydrogen; there is formation of a very strong cosmological wind mostly alongside the alignment of rotation. This therefore means that several young stars have got a bipolar outflow which simply is a flow of gas outside the star’s pole. This characteristic is readily witnessed by use of radio telescopes. Thus this initial phase in a star’s life is referred to as the T-Tauri phase. A very prominent result of this breaking up is the fact that youthful T Tauri stars are generally bordered by enormous circumstellar disks that are opaque. These disks later on accrete onto the cosmological surface thereby radiating energy from both the disk (infrared wavelengths) as well as from the location where substance cascades onto the star at (ultraviolet and optical wavelengths).in some way some of the fraction of substance accreted onto the star is evicted upright to the disk’s plane in an exceedingly collimated stellar jet. Thus the circumstellar disk eventually scatters most likely when the planets start forming. Youthful stars usually have got spots that are dark on their surfaces and are similar to sunspots but they however cover a much bigger fraction of the star’s surface area. Thus T Tauri stage can be described as the phase when stars have strong cosmological winds, surface activity (eruptions, flares) that is vigorous, irregular and variable light curves. Stars while at T-Tauri stage can lose up to half of its initial mass before finally settling down as a major sequence star. Thus stars at this stage are known as pre-main sequence stars (Peter, 2011). Evolution of T-Tauri stars T-Tauri stars will eventually evolve onto the major sequence. They usually start their lives as somewhat cool stars, heats up and later becomes bluer and somewhat fainter, something which is dependent on their original mass. Very huge youthful stars are born so quickly that they just emerge on the major sequence with a very small T-Tauri stage that no one ever observes them. T-Tauri stars are constantly found entrenched in the gas clouds from which they were originally born. For instance, the Trapezium cluster of stars within the Orion Nebula is a classic example (Lee, 2000). The Evolution of youthful stars is from a group of protostars inside the core of molecular clouds, to a group of stars of T-Tauri phase whose cosmological winds and hot surfaces warm up the neighboring gas forming an HII(H-two or ionized hydrogen) region. Afterwards the group collapses, blowing the gas away, making stars to evolve into other forms. Frequently in galaxies, we discover groups of young stars close to other youthful stars, a phenomenon referred to as supernova induced star formation. Thus the very huge stars first form and then explode into supernova, making shock waves into molecular cloud leading to compressing of nearby gas thus forming more stars. A type of stellar coherence is allowed to form and is usually the reason for the pinwheel patterns that are mostly seen in galaxies (Lee, 2000). Main sequence stars Large stars such as the Sun needs around fifty million years to become mature from the starting of the break up to adulthood. The Sun will stay in this state of maturity for another estimated ten billion years. Nuclear fuses with hydrogen forming helium deep inside their cores. This energy outflow from the star’s core regions gives pressure that is necessary to maintain the star from breaking up due to its own weight and also the energy which enables it to shine. Main sequence stars have a wide range span of colors and luminosities and can thus be categorized according to such features (Naveed, 2008). The tiniest stars referred to as red dwarfs may hold as small as 10% of Sun’s mass and usually gives off only 0.01% energy, glowing weakly at temperature range of 3000-4000K.In spite of them being tiny, red dwarfs are definitely the most abundant stars in the whole Universe and their life spans range to tens of billions of years. Alternatively, big stars referred to as hyper giants may be more than 100 times larger than the Sun, with surface temperatures of over 30,000 K. These massive stars give out more energy over hundred thousand times more than the Sun, however they have a short lifespan of only a few million in years. Whereas stars such as these of great extremes are thought to have been widespread in the era of early universe, they are extremely rare nowadays and for instance the whole Milky Way galaxy has got only a few of them. Stars and their fate Generally, the bigger the star, the shorter is its life span even though the very massive ones may exist for a several billion years. Nuclear reaction stops the moment a star’s hydrogen inside its core is completely fused. Dispossessed of all the energy production required to sustain it, the star’s core starts to break up into itself becoming much hotter. There is still some hydrogen available outside of its core and thus fusion of hydrogen goes on in a shell neighboring the core. The outside layers of star are pushed outwards by the progressively hotter core leading to their expansion and cooling, making the star to become one red giant(Naveed,2008). For stars that are average such as the Sun, the process of ejection of its outward layers goes on till the exposure of the stellar core. This extinct but still viciously hot cosmological cinder is referred to as White Dwarf. They are usually Earth’s size even though they contain the mass of a star and are kept from breaking up by pressure from fast moving electrons. The large the core of the star the denser will be the white dwarf that is created. Interestingly the smaller the white dwarf’s diameter, the bigger it’s mass will be! Availability of these paradoxical stars is widespread and the Sun will become a white dwarf a few billion years from now. Because of their diminutive nature and lacking any energy production source, white dwarfs are typically very faint .They thus slowly fade into nothingness as they cool down gradually. This kind of fate is experienced by stars whose mass is about 1.4 times the Sun’s mass. If the mass is above that, electron pressure will not sustain the core against any more collapsing. Such kinds of stars experience a different kind of fate. Conclusion Formation of stars is thus a complex process which happens under very extreme temperatures and speeds. Key components of formation of stars are only obtainable by observation in terms of wavelengths rather than optical. Thus some stages of cosmological existence like protestellar is almost perpetually hidden away deep within the very dense dust and gas clouds left behind from the gigantic molecular clouds (GMC) .The formation of specific stars can only directly be observed within our galaxy. However in far away galaxies, formation of stars has been noticed through its distinct spectral signature. On 24th February this year, NASA reviewed that a significantly upgraded database for polycyclic aromatic hydrocarbons (PAHs) tracking within the universe. Scientists believe that over 20% of the total carbon within the universe may be related with these PAHs, which according to them are probable beginning substances for life formation. PAHs are likely to have been created a short while following the Big Bang, are common throughout the universe and are related with formation of new exoplanets and stars (John, 2005). References John, T. (2005). Advances in Astronomy:From the Big Bang to the Solar System. London: Imperial College Press. Lee, H. (2000). Accretion Processes in Star Formation. New York: Cambridge University Press. Naveen, R. (2008). A Multi-Wavelength Census of Star Formation at Redshift. New York: Naveen Reddy. Peter, B. (2011). Principles of Star Formation. New York: Springer. Tenorio, T. (2000). Violent Star Formation. London: Cambridge University Press. Whitworth A, Thompson. D. (2012). An Introduction to Star Formation. New York: Cambridge. Read More