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Student Guide to Activity 1: Features of the Sun

Problem: What do the following features look like on photographs of the Sun: sunspots, plages, solar flares, prominences, filaments, the corona, helmet streamers, and coronal holes? How do these features compare and contrast?

Caution: Never look directly at the Sun. To view the Sun, project an image through a card or sheet of notebook paper, pierced with pin sized hole, onto a sheet of white paper. The Sun’s inverted image will appear on the paper below.

Introduction

Our Sun is a middle-aged, medium sized star, big enough to hold a million Earths. The ancient Greeks thought that the Sun was a perfect sphere of fire. Today we know that the Sun is a variable (changeable) star that produces life giving light and heat as well as harmful radiation. It causes space weather that can harm astronauts working in space and can interfere with satellites orbiting our planet.

Features of the Sun’s Surface and Atmosphere:

Although the average distance from Earth to the Sun is a whopping 149,600,000 kilometers (93,000,000 miles), careful observation from Earth reveals a surprisingly large number of different visible features. The most obvious and best known feature is the sunspot. Typically moving in groups, these dark (in visible light), planet-sized features have been known to humankind for centuries. As sunspots form and disappear over periods of days or weeks, they also appear to move across the Sun’s surface. Composed of strong magnetic fields, sunspots are shaped much like a horseshoe magnet that rises from below the Sun’s surface. More accurately, however, flexible magnetic tubes, or “flux tubes,” probably give rise to the magnetic fields that we see. The rising hot gas is trapped by the sunspots’ intense magnetic field which cools the sunspots from 6000 ½C to about 4200 ½C. The cool area appears dark compared to the area around it. Sunspots N

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Student Guide, Activity 1: Features of the Sun

© Space Science Institute, 1999. All Rights Reserved

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