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Chapter 10Book Notes

Chapter 10Book Notes - Astronomy 180 Chapter 10 The Sun Our...

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Astronomy 180 Chapter 10: The Sun: Our Extraordinary Ordinary Star (Pages 267-288) The sun shows a brilliant disk of light no larger than then moon, yet is of staggering mass and size The sun contains as much mass as 333,000 Earths Some of the energy rushing into space from the Sun is essential to maintaining Earth’s habitability: ultraviolet radiation, visible light, and infrared radiation By studying the Sun, astronomers have come to learn how most stars in the universe work, despite the fact that the Sun is not ordinary among most stars I. The Sun’s Atmosphere Although there is a solar “surface,” the Sun is so hot that it has neither liquid or solid matter inside of it (only gas) II. The Sun’s Atmosphere: The photosphere is the visible layer of the Sun Photosphere “sphere of light” the region in the solar atmosphere from which most of the visible light escapes into space; innermost of the 3 layers of the Sun’s atmosphere The photosphere is 0.01% as thick as the air we breathe, has a blackbody spectrum and an average temp of 5800K The upper two layers are transparent to most wavelengths of visible light, so we can see through them; everything below the photosphere is considered the Sun’s interior Limb – the apparent edge of the Sun as seen in the sky Limb darkening – the phenomenon whereby the Sun is darker near its limb than near the center of its disk Granules – lightly colored convection features about 1000 km in diameter seen constantly in the solar photosphere The gasses in granules rise and fall, caused by convection III. The Sun’s Atmosphere: The chromosphere is characterized by spikes of gas called spicules Chromosphere “sphere of color” the layer in the solar atmosphere between the photosphere and the corona During an eclipse, the chromosphere is a visible pinkish strip ~2000 km thick around the edge of the dark moon Spicule – a narrow jet of rising gas in the solar chromosphere Supergranule – a large convective cell in the Sun’s chromospheres containing many granules IV. The Sun’s Atmosphere: Temperatures increase higher in the Sun’s atmosphere Corona – the Sun’s outer atmosphere Transition zone – region between the Sun’s chormosphere and corona where the temperature skyrockets to about 1 million K The hotter a gas is, the more it is ionized; the corona contains a large number of highly ionized elements The density of gas in the corona is VERY low, attributing to the dimness of the corona Solar wind – an outward flow of particles (mostly electrons and protons) from the Sun Heliosphere – a bubble in space containing the Sun and planets created by the solar wind that prevents most of the gases flowing in space from other stars from entering our solarsystem Electrons and hydrogen and helium nuclei comprise 99.9% of the solar wind By the time that the solar particles reach the vicinity of the Earth, they are very spread out V. The Active Sun
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