SSDO | Solar Dynamics Observatory - Living With a Star

LIVING WITH A STAR

Did you know that our Sun is actually a star?

If not, don't feel bad... many adults don't even know! Go ahead, ask your parents and see what they say. Hey, you might even teach them something they didn't know!

Many people don't realize our Sun is a star because it doesn't look like the ones we are used to seeing in the sky, it "appears" much much bigger. But actually, it isn't bigger... it's just much closer to us. Our Sun is really only an average star. There are billions of other stars out there that are much larger than our star and just as many that are much smaller!

The average lifespan of a star like ours is 10 billion years. Our sun is about 5 billions years old... halfway through its life cycle. In about 5 billion years, when the Sun nears the end of its life it will grow to be a huge, red burning ball, called a red giant, swallowing up Mercury, Venus, Earth, and maybe even Mars! Who knows, by this time, we may even be living on other planets or in other Solar Systems! Then it will start to shrink down, to much smaller than its current size, and become a white dwarf. It will burn like that for a long time and then eventually simply burn out or explode as a supernova.

OK, now that you know that the Sun is an average Star and you know about its life cycle, what else do you know about the Sun?

Did you know that the Sun is the center of our Solar System and everything in our solar system (Earth, the other planets, comets, asteroids...) orbits around it? This is due to its mass, gravity, something called inertia and a whole lot of other strange laws of physics. Nonetheless, we are going around and around and around, 24 hours a day seven days a week. In fact, we have hours, days, weeks and even years because everything in the solar system is constantly moving.

Our Sun is mostly made of hydrogen and much of the rest of it is helium. There are a few other ingredients in there but all together they only make up about 0.1% of the Sun. The Sun is actually a plasma, not quite a solid but not quite a gas either.

THE SUN HAS SIX LAYERS

CORE:

The innermost layer of the Sun where all of the Sun's energy is produced through nuclear fusion. This conversion of hydrogen to helium powers the Sun and produces all of the heat and light we receive on Earth. The core has a density of more than 150 times that of water!

RADIATIVE ZONE:

The innermost shell right above the core where energy is carried outwards by radiation. Here the plasma density is very high and the radiation gets bounced around following a zig-zag path outward. It takes about 170 thousand years for radiation to make its way from the core to the top of the radiative zone!

CONVECTIVE ZONE:

The outermost shell surrounding the core where plasma is too cool and opaque to allow radiation to pass. Instead, huge convection currents form and large bubbles of hot plasma move up towards the surface (similar to a boiling pot of water heated on a stove).

PHOTOSPHERE:

The Sun's visible surface has a temperature of about 6,000K. It is often marked by the presence of sunspots which appear dark because they are about 2,500K cooler than the surrounding photosphere.

CHROMOSPHERE:

A thin layer just above the photosphere. The name chromosphere is derived from the word chroma, the Greek word for Color. It can be detected in red hydrogen-alpha light meaning that it appears bright red. The chromosphere is often seen for a few seconds just as a total eclipse begins and ends.

CORONA:

The outermost layer of the Sun. The corona extends millions of kilometers into space and is visible only during total solar eclipses. Its temperature is about 2,000,000K.

When the light finally escapes the Sun's surface, it only takes it about eight minutes to reach us on Earth. Can you believe that the light and heat we get today on Earth was created over 200 million years ago in the middle of the Sun!