The Sun

[image credit NASA]

Solar Filter Warning

CRITICAL SAFETY WARNING — READ BEFORE doing THIS ACTIVITY

NEVER look directly at the Sun without proper eye protection. Looking at the Sun through a telescope without proper protection can cause permanent blindness.

The telescope MUST have the solar filter properly installed to be able to complete this activity!

Page 1: Information

The Sun is a 4.5 billion-year-old yellow dwarf star sitting at the heart of our Solar System, approximately 93 million miles from Earth. Composed almost entirely of hydrogen and helium, it is the largest object in our Solar System and by far the closest star to Earth. It is so massive, that over 1.3 million Earths could fit inside it! Its gravity holds everything in our Solar System in orbit, from the largest planets to the smallest fragments of debris.

Despite its size, the Sun is considered an average star. What makes it remarkable is its immense energy output. At its core, nuclear fusion reactions reach temperatures of 27 million degrees Fahrenheit, fusing hydrogen into helium and generating the heat and light that make life on Earth possible. The visible surface, called the photosphere, is a comparatively cooler 10,000 degrees Fahrenheit, still hot enough to vaporize diamonds.

The Sun has several distinct layers. Energy produced in the core travels outward through the radiative zone, a process that takes roughly 170,000 years, before reaching the convection zone where hot plasma rises toward the surface. Beyond the photosphere lie the chromosphere and the corona, which is the Sun's outer atmosphere. The corona paradoxically reaches temperatures of up to 3.5 million degrees Fahrenheit, far hotter than the surface below it.

The Sun orbits the center of the Milky Way, completing one full trip approximately every 230 million years. Scientists estimate it is roughly halfway through its 10-billion-year lifespan. When it eventually dies, it will expand into a red giant, potentially engulfing the inner planets, before collapsing into a white dwarf.

Every beam of sunlight you see through this telescope began its journey at the Sun's core hundreds of thousands of years ago.

Page 2: Questions

1. Why do sunspots appear dark if they are still thousands of degrees?
2. Sunspot activity follows an 11-year cycle, swinging between a solar minimum with very few sunspots and a solar maximum with many. How does this compare to what you counted in your observations, and what phase of the cycle might the Sun currently be in?
3. Astronomers began counting solar cycles in 1755. If Solar Cycle 1 ended that year, what solar cycle is the Sun in now?
4. The Sun is a star. Do you think other stars have sunspots?

Solar Filter

• Treat the solar filter like glass. Once it is damaged it must be destroyed and disposed of so that no-one can mistakenly use it. A damaged filter can damage your eyesight.
• Supervise students at all times when the telescope is pointed at the Sun.
• Only use a solar filter that is designed for YOUR telescope.

Finder Scope

• Even looking through the Finder Scope at the Sun can cause permanent blindness. Even though it has no lens, you would still be staring at the unfiltered Sun. Do not use the finder scope when observing the Sun.

Page 3: Directions

1. DO NOT complete this activity or view the Sun unless you have a solar filter.
2. Inspect your solar filter carefully for any damage before attaching it.
3. Attach the solar filter securely to the front (objective) end of the telescope before pointing the telescope towards the Sun.
4. Point the telescope toward the Sun using the shadow of the telescope tube to guide you and align the tube so its shadow is as small and circular as possible.
5. Once aligned, look through the eyepiece. You should see an orange-tinted disk. Adjust focus slowly until the edge of the Sun appears sharp.
6. Scan the surface for sunspots. They appear as small dark spots or clusters. Note their location (center, edge, north, south) and count them.
7. Fill in the recording table and sketch what you see in the circles.
8. Point the telescope away from the Sun before removing the solar filter.
9. Repeat on different days to track how sunspots move and change.

Page 4: Recording Sheet

Observation Log

Sunspot Sketches

In each section below, sketch the Sun as you see it. Mark sunspots with small filled dots and label any notable clusters.