# Essay: Astronomy Questions

###### Essay: Astronomy Questions

Sample Essay

Question A-J. Answer with approx. 50 words. Short correct answers are ok.

a.       Light is one form of electromagnetic radiation. What are electromagnetic waves and what other types are there besides visible light? Compare the wavelengths of the different type of electromagnetic radiation. What is the relationship of frequency and wavelength for electromagnetic waves? What is the Speed of Electromagnetic Waves as they travel through space?

Electromagnetic waves consist of two components. One is electrical and the other is magnetic. Their speed is equivalent to that of light (300000 kilometers/sec) when they travel through space. Light contains waves which have wavelengths of about 10-7 meters. Other types of electromagnetic radiations are X-rays which have shorter wavelengths then light ranging from 10-9 to 10-12 meters and microwaves which have wavelengths from 0.001 to 0.3 m. The frequency of electromagnetic waves also increases and decreases with wavelength (European Space Agency, 2004).

b.       How can the temperature, composition, and motion of a star be determined from its light spectrum?   What is the definition of Luminosity?

Cooler object tends to give out more radiations of higher wavelengths then hotter ones. Determining the position at which the spectrum peaks will determine its temperature. Since each element gives out or absorbs light of a particular wavelength, by analyzing the light spectrum of the star, we can figure out the corresponding elements from the wavelengths and thus find the composition of the star. The motion of the star can be determined by measuring the number of crests that are met. Luminosity is defined as the amount of energy released by a body per unit time (Bennett, Donahue, Schneider & Voit, 2000).

c.       Why do astronomers infer that the Sun’s energy comes from nuclear fusion reactions rather than chemical reactions? How do we know it cannot possibly come from a chemical process? Who was responsible for proposing nuclear energy powers the stars (not Einstein)?

Astronomers believe that the source of Sun’s energy is nuclear fusion reactions because that age of the sun is estimated to be at least 4.54 billion years. No chemical reaction can sustain itself for such a long time. We know it for sure, because the temperature at the core of sun is in millions of Kelvin which is too high for bonds to exist and thus chemical reactions cannot happen. Sir Arthur Eddington was the person who, in 1920, proposed that the nuclear energy powers the stars (Hsu, Chaniotakis, Damelin & Carlisle, 2009).

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