![]() Most of the elements found in the Sun are in the form of atoms, with a small number of molecules, all in the form of gases: the Sun is so hot that no matter can survive as a liquid or a solid. (And, as we will see, the composition of the Sun and the stars is much more typical of the makeup of the universe than the odd concentration of heavier elements that characterizes our planet.) It was 3 years after her thesis that other studies proved beyond a doubt that the enormous abundance of hydrogen and helium in the Sun is indeed real. At the time, she wrote, “The enormous abundance derived for these elements in the stellar atmosphere is almost certainly not real.” Even scientists sometimes find it hard to accept new ideas that do not agree with what everyone “knows” to be right.īefore Payne-Gaposchkin’s work, everyone assumed that the composition of the Sun and stars would be much like that of Earth. ![]() However, the idea that the simplest light gases-hydrogen and helium-were the most abundant elements in stars was so unexpected and so shocking that she assumed her analysis of the data must be wrong. The fact that our Sun and the stars all have similar compositions and are made up of mostly hydrogen and helium was first shown in a brilliant thesis in 1925 by Cecilia Payne-Gaposchkin, the first woman to get a PhD in astronomy in the United States (Figure 2). Yet, being a woman, she was not given a formal appointment at Harvard, where she worked, until 1938 and was not appointed a professor until 1956. Cecilia Payne-Gaposchkin (1900–1979): Her 1925 doctoral thesis laid the foundations for understanding the composition of the Sun and the stars. The Abundance of Elements in the Sunįigure 2. (In our planet’s crust, the three most abundant elements are oxygen, silicon, and aluminum.) Although not like our planet’s, the makeup of the Sun is quite typical of stars in general. Examine that table and notice that the composition of the Sun’s outer layer is very different from Earth’s crust, where we live. The 10 most abundant gases in the Sun’s visible surface layer are listed in Table 1. All the other chemical elements (including those we know and love in our own bodies, such as carbon, oxygen, and nitrogen) make up only 2% of our star. About 73% of the Sun’s mass is hydrogen, and another 25% is helium. It turns out that the Sun contains the same elements as Earth but not in the same proportions. As explained in Radiation and Spectra, we can use a star’s absorption line spectrum to determine what elements are present. Let’s begin by asking what the solar atmosphere is made of. Sunspots and Doppler shift in spectra taken at the edge of the Sun Solar constant × area of spherical surface 1 AU in radiusĭerived from luminosity and radius of the Sun Instrument sensitive to radiation at all wavelengths Gravitational acceleration at photosphere (surface gravity) Although some of the terms in that table may be unfamiliar to you right now, you will get to know them as you read further. Some of the basic characteristics of the Sun are listed in Table 1. ![]() (credit: modification of work by SOHO/EIT/ESA) Earth and the Sun: Here, Earth is shown to scale with part of the Sun and a giant loop of hot gas erupting from its surface. Unlike many faint objects in the night sky, the Sun is easy to locate and track during the day.Figure 1. Solar observing has many benefits for amateur astronomers. With the right equipment, many fascinating and beautiful features can be seen on the visible face of the Sun with a small telescope or binoculars, and you can enjoy special events such as total and partial solar eclipses and transits of planets and other objects across the face of the Sun. As you are about to discover, when you become a regular observer of our home star, there's quite a bit for you to see. But the daytime sky offers an opportunity to examine-close up-the seething face of a major star, the Sun, the nearest star to Earth. Most stargazers spend most of their time observing sights in the night sky. Color Correction & Minus Violet Filtersįigure 1.1 – An image of the solar disk showing light emitted at the hydrogen-alpha wavelength of 656.3 nm.Correctors, Focal Reducers & Flatteners. ![]()
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