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Chapter 15 16 Astronomy Notes.docx - Chapter 15 Astronomy...

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Chapter 15 Astronomy NotesTHE SUN: A GARDEN VARIETY STAR“Space Weather” refers to changing conditions in space. These effects can have profound effectson Earth.Even though the Sun is a far distance off, there are solar storms that affect us and cause changesin the magnetic field of Earth.How does the composition of the Sun differ from that of Earth?What are the various layers of the Sun and their functions?Explain what happens in different parts of the Sun’s atmosphere.The Sun could fit 109 Earths side-by-side across its diameter, and has enough volume to holdabout 1.3 million Earths.The Sun does not have a solid surface or a solid core. Think of the Sun like an onion.Composition of the Sun’s AtmosphereSolar Atmosphere? We can use a star’sabsorption line spectrumto determine what elements arepresent.The Sun contains the same elements as Earth but not in the same proportions.73% of the Sun’s mass ishydrogenand 25% ishelium. All other chemical elements, even thosein our own bodies (like carbon, oxygen, nitrogen) make up only 2% of our star.The 10 most abundant gasses in the Sun’s visible surface layer are listed. The composition of theSun’s outer layer is very different from Earth’s crust, where we live. (In Earths crust, the threemost abundant elements are oxygen, silicon and aluminum).The fact that our Sun and the stars all have similar compositions and are made up of mostlyhydrogen and heliumwas first shown in a thesis in 1925 byCecelia Payne-Gaposchkin, thefirst woman to get a PhD in astronomy in the United States.The idea that the simplest of light gasses were the most abundant element in stars was sounexpected and shocking that she assumed her analysis of data must be wrong.Before her work, everyone assumed that the composition of the Sun and stars would be like thatof Earth. It was only 3 years after her thesis that other studies proved beyond a doubt that theabundance of hydrogen and helium in the Sun is real.Most of the elements found in the Sun are in the form of atoms, with a small number ofmolecules, all in the form of gasses. The Sun is so hot that no matter of liquid can survive, or asolid. The Sun in fact, ionizes the atoms. The removal of electrons from their atoms means that
there is a large quantity of free electrons and positively charged ions in the Sun making it anelectrically charged environment.Scientists call this hot ionized gasplasma.Scientists observed a spectral line at 530.3 nanometers in the Sun’s outer atmosphere called thecorona. This layer had never been seen before and so it was assumed that this line was the resultof a new element found in the corona, namedcoronium.The Sun’s layers are different from each other and each plays a part in producing energy that theSun emits.The Sun’scoreis extremely dense and is the source of all its energy. There, nuclear energy isreleased. It is approximately 20% of the size of the solar interior and is thought to have a

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Term
Summer
Professor
NESTOR CASTELLANOS
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