02 The Sun-online

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School

University of Texas, Rio Grande Valley *

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1402

Subject

Astronomy

Date

Feb 20, 2024

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docx

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Uploaded by CorporalCrocodileMaster789

Astronomy 1402 - Online The Sun The purpose of this laboratory activity is to learn about the sun including its apparent motion, sunspots and layers.

p. 2 Part 1: Background Galileo was the first person to record the sunspots and their motion and realize that this meant that the sun was rotating on its own axis. This was a surprising and exciting idea in the 1600s because it meant that the Earth was not the center of all motions. When Galileo made his first discoveries there were no cameras, and all images had to be drawn. Each sunspot has a position on the sun’s surface, which can be specified by latitude and a longitude, just as places on the Earth. Because the sun spins on its own axis, it has an equator as well as a north pole and south pole. Since the plane of the Earth’s orbit around the sun is almost in the same plane as the sun’s equator, we see the sun’s equator almost in the middle of the sun’s face. As the sun appears to move in the daytime sky, its height or altitude increases from sunrise until local noon, then decreases until sunset. As the altitude changes, so does the length of a shadow. When the sun is low on the horizon, a shadow can be very long (in fact, it may not even be measured). When the sun reaches its zenith or high point at noon, a shadow is very small. Some people would say that there is no shadow. By measuring the length of a shadow, the altitude of the sun can be determined. Altitudes on the celestial sphere are measured by angles because earthbound observers have no concept of depth beyond a few hundred meters. During the day, the sun’s direction from North or azimuth or bearing also changes. In the northern hemisphere above the tropics, the sun is always in the southern sky, but travels across it form east to west. Refraction of light by the atmosphere causes the sun to appear to be in the northern half of the sky at times especially close to sunrise and sunset. By holding a compass in a shadow, the sun’s azimuth or direction can be measured. The sun contains different layers that can be divided into two categories. The inner layers include the Inner Core, the Radiative Zone and

p. 3 Convection Zone. Photosphere, Chromosphere, and the Corona comprised the outer layers of the sun. In the Core, the temperature is at its highest temperature, and it begins to decrease from the core to the convection zone. Then, in the outer layers, the temperature increases from the photosphere to the corona. Below is a diagram that illustrates the layers of the sun. Solar Vocabulary: Aurora - Faint lights in the night sky caused by the sun’s emissions. Corona - The part of the solar atmosphere only visible to the naked eye during a solar eclipse. Differential Rotation - The different speeds of rotation of the Sun’s surface. Disk - The round appearance of the surface to the sun against the sky Penumbra - The outside area of a sunspot made up of dark and bright features. Photosphere - The surface of the sun that is visible to us, where sunspots can be seen. Plage - A faint, large, bright area around most sunspots. Prominence - Dark filaments seen on the sun’s surface which stand off from the limb when viewed on edge.

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