Welcome to Gaia! :: View User's Journal | Gaia Journals

How heavy is the Sun?
Although we cannot actually weigh the Sun with a scale, we can compute its weight by studying the way it affects other objects, like the Earth. We do know that it contains virtually all the mass in our solar system! We can also understand this better by making some comparisons. Since the Sun is so much more massive than the Earth (over 300,000 times heavier) its gravitational pull is also much larger. A child that weighs 75 pounds on Earth would weigh about a ton on the Sun. The weight increases by a factor of 30. (Of course, we cannot really stand on the Sun, for it is too hot and has no solid surface.)

How old is the Sun?
The Sun is about 4 1/2 billion years old. Humans have only been around for a tiny, tiny fraction of this time. As a comparison, if you think of 4.5 billion years as the length of a 12 inch ruler, then the time humans have existed wouldn't even be the width of the lines marking the inches. (Metric equivalent is 30.5cm and it would still be just the width of the markings.)

The Sun will remain more or less the way it is now for about another 5 billion years. After that, it will exhaust the hydrogen it currently "burns" and will enter a new phase of existence. During this phase the Sun will begin "burning" helium and will expand to about 100 times its current size and become what is called a red giant. Once it runs out of helium it will collapse into a much smaller object called a white dwarf.

How hot is the Sun?
The Sun is extremely HOT! The middle of the Sun is at least 10 million degrees. The "surface" of the Sun (what we see) is only 5800 degrees. This is cool for the Sun, but is actually about 16 times hotter than boiling water (ouch!). The outer atmosphere of the Sun (which we don't really see with our eyes) gets extremely hot again, about 1.5 to 2 million degrees. These huge temperature changes are very interesting to scientists.

Can the Sun be dangerous?
Never look directly at the Sun, even with sunglasses. The human eye is not made to look at an object that bright. It is so bright it could easily blind you in just a few seconds. Have you ever looked at a bright light bulb and then had to look away after a short time? Well, the Sun is about a million times brighter than a household light bulb. This is why you can injure your eyes: if you look directly at the Sun, the inside of your eyes can burn severely and may never heal again. You could lose your sight permanently. In order to study the Sun, scientists look directly at the Sun only with the aid of special instruments that are made to tolerate the extreme brightness.

The Sun also emits harmful ultraviolet (UV) radiation, which can damage your skin and eyes. In fact, any tan is a sign of damage to your skin! A sunburn may hurt for a while, but damaging your skin over many years can cause many problems, including skin cancer. That is why you should always wear sunscreen of SPF 15 or higher when you will be out in the Sun for more than a few minutes. This applies even for cloudy days -- though not as bright as sunny days, much of the harmful UV light still comes through. Note that having a tan is little protection from skin damage, providing an SPF of only about 2.

To help protect your eyes, use sunglasses that filter 100% of UV light. When you buy glasses, check for labels that say 100% UV Protection. People who don't protect their eyes when they are young run the risk of loss of sight when older, including getting cataracts .
Why do we study the Sun?
Without the Sun, life on Earth would not exist. Our planet would be a frozen dark ball, drifting dead in space. We need the Sun for light, heat and energy. With the Sun, plants can grow, and animals can eat. The Sun's output changes over time. These changes affect not only our daily lives and climate, but also our communications, such as by satellites. The more we know about the Sun, the better we can deal with these changes.

In the past, we know the Sun was a little different than it is now, and at those times the Earth experienced ice ages. During the most recent ice age, almost all of Canada and the Northern US was covered in a huge sheet of ice about a mile thick! (That's about 1.6 km.) Even recently (the late 1600s) Europe and North America were a bit cooler than they are now, experiencing a little ice age, and changes in the Sun were most likely responsible.