Astronomy 101: Studying the Sun

Lesson 8: Visiting Close to Home

Image of our sun, Sol.
Image of our sun, Sol. NASA

What Is a Solar System?

Everyone knows we live in a neighborhood of space called the solar system. What is it, exactly? It turns out that our knowledge of our place in space is changing radically as we send spacecraft to explore it. It's doubly important to know what a solar system as telescopes study planetary systems around other stars, as well.

Let's examine the basics of the solar system.

First, it consists of a star, orbited by planets or smaller rocky bodies. The gravitational pull of the star holds the system together. Our solar system consists of our sun, which is a star called Sol, nine planets including the one we live on, Earth, along with the satellites of those planets, a number of asteroids, comets, and other smaller objects. For this lesson, we'll concentrate on our star, the Sun.

The Sun

While some stars in our galaxy are nearly as old as the universe, about 13.75 billion years, our Sun is a second-generation star. It is only 4.6 billion years old. Some of its material came from former stars.

Stars are designated by a letter and a number combination roughly according to their surface temperature. The classes from hottest to coolest are: W, O, B, A, F, G, K, M, R, N, and S. The number is a subcategory of each designation and sometimes a third letter is added in to refine the type even further. Our Sun is designated as a G2V star. Most of the time, the rest of us call it "the Sun" or "Sol". Astronomers describe it as a very ordinary star. 

Since its creation, our star has used up about half of the hydrogen in its core. Over the next 5 billion years or so, it will grow steadily brighter as more helium accumulates in its core. As the supply of hydrogen dwindles, the Sun's core must keep producing enough pressure to keep the Sun from collapsing in on itself. The only way it can do this is to increase its temperature. Eventually, it will run out of hydrogen fuel. At that point, the Sun will go through a radical change which will most likely result in the complete destruction of the planet Earth. First, its outer layers will expand, and engulf the inner solar system. The layers will escape out to space, creating a ring-like nebula around the Sun. What's left of the Sun will light up that cloud of gases and dust, ​creating a planetary nebula.  That remaining remnant of our star will shrink down to become a white dwarf, taking billions of years to cool. 

Observing the Sun

Of course, astronomers study the Sun every day, using ground-based solar observatories and orbiting spacecraft specially designed to study our star.

A very interesting phenomenon associated with the Sun is called an eclipse. It happens when our own Moon passes between the Earth and the Sun, blocking out all or part of the Sun from view. 

Warning: observing the Sun on your own can be quite dangerous. It should never be viewed directly, either with or without a magnifying device. Follow good viewing advice when seeing the Sun. Permanent damage can be done to your eyes in a fraction of a second unless proper precautions are taken. There are filters which can be utilized with many telescopes.Consult someone with a lot of experience before attempting solar viewing. Or better yet, go to an observatory or science center that offers solar viewing and take advantage of their expertise. 

Sun Statistics:

  • diameter: 1,390,000 km.
  • mass: 1.989e30 kg
  • temperature: 5800 K (surface) 15,600,000 K (core)

In our next lesson, we'll take a closer look at the inner solar system, including Mercury, Venus, Earth, and Mars. 


Read more about star color classification, the Milky Way, and eclipses

Ninth Lesson > Visiting Close to Home: The Inner Solar System > Lesson 9, 10

Edited and updated by Carolyn Collins Petersen.