A) Our Sun

What is the closest star to our planet? That’s right, the Sun. The Sun is Earth’s source of light. Sunlight is important for life here on Earth. The plants on Earth use energy from sunlight to grow. This process is called photosynthesis. Sunlight is also a great source of Vitamin D for us kids.

In fact, if we did not have the Sun’s warm rays our Earth would be a frozen ball of ice. Only a small amount of heat comes from the Earth itself from sources such as hot springs and volcanic eruptions.

We know sunlight warms the Earth and feeds the plants that nourish our bodies with important vitamins; but the Sun’s rays also can be harmful. Over time ultraviolet rays can harm plants’ photosynthesis. These rays also can burn our skin, even causing cancers. Ultraviolet rays are part of the Sun’s natural radiation, and projects like NASA’s SORCE takes measurements of incoming solar radiation so that we can learn more about sunlight that reaches the Earth.

The Sun’s energy is such a powerful force in all human activity which is why NASA began to launching satellites into space so we can understand the Sun and its affect on Earth. When the United States launched its very first satellite in 1958, called the Explorer 1, this satellite carried an instrument for detecting cosmic rays. Cosmic rays are particles that constantly come to Earth from space; much like a steady rain falling on Earth, only this is constantly coming from space.

What is the Sun like?
Like the Earth, the Sun is made up of six different layers. However, unlike the Earth, the Sun is a gigantic ball of gas that has no solid surface. The Sun is so big that more than a million Earths could fit inside. NASA’s satellite instruments of the SoHO and the IRIS missions help us to better understand what is in the inside of the Sun.

B) Our Solar System

What is the Solar System?
At the center of our Solar System is the Sun, a yellow star. The Solar System is also made up of planets, moons, comets, asteroids and space rocks, ice, and several dwarf planets that all orbit around the Sun. In the 16th and 17th centuries, Galileo and Isaac Newton studied the Sun, and learned that the planets orbit the Sun due to gravity.

If you and your friends sit on a merry-go-round and don’t hold onto anything, you’ll move from the center as it spins. But what if strong grown-ups sitting in the center are holding onto you? Then you will stay in place, right? The Sun’s gravitational pull acts much the same way with the planets. Everything in the Solar System revolves around the Sun while the Sun’s gravity holds the planets in an orbit at a stable distance instead of moving farther away – just like the grown-ups on the merry-go-round. In addition to planets, the Solar System consists of Moons, comets, asteroids, minor planets, dust and gas, all orbiting around the Sun.

How did the Sun and the Solar System form?
The creation of our Solar System took place about 5 billion years ago.Scientists believe that the Solar System formed from a giant cloud of dust and gas. This dust and gas began to collapse into a small spinning pancake because of its own gravity. At the center of this spinning flat cloud, a small star began to form and clumps in the cloud began to form the planets. This star grew larger and larger as it collected more and more of the dust and gas that collapsed into it becoming hotter and hotter. Eventually, when it reached a temperature of around 1 million degrees, its core ignited and the Sun began to produce energy.

How scientists go about solving a mystery like how the Solar System was created can be every bit as exciting as the answers they find. If our Solar System were a puzzle, the planets would be the larger puzzle pieces, and comets would be the smaller puzzle pieces. Comets are small pieces of ice and dust that fly in the big spaces between planets. Studying comets can help us see the big picture of how the Solar System may once have fit together, and how it began. The challenge for us is, comets are hard to catch! In 2004, the European Space Agency launched a spacecraft called Rosetta designed to orbit a moving comet and then send some NASA instruments to the comet’s surface to see what the comet is made of. Rosetta and other spacecraft today uses solar cells for power which are similar to the solar panels we use on Earth to convert the Sun’s energy into power. So, to study the Sun and Solar System we can use the Sun’s own energy. Thanks again, Sun!

C) Sunspots and Space Weather

The Sun is far too hot for an astronaut to ever visit, but there are areas on the Sun that are slightly cooler than others. These areas are known as sunspots. Sunspots are still very hot - thousands of degrees! Because they are slightly cooler than the rest of the Sun’s surface, they appear slightly darker in color.

Of course, you cannot look directly at the Sun to see these spots because you would hurt your eyes. Astronomers have to use special telescopes with filters and other instruments to view the cooler spots on the surface of the Sun.

A sunspot can last for an hour or two, or, as long as several months. The number of sunspots that can be seen on the surface of the Sun changes in a regular pattern, known as the solar cycle, with the most sunspots occurring every 11 years.

On January 1, 2014, the Solar Dynamics Observatory, or SDO for short, caught sight of the largest sunspot ever. It measured two entire Earths wide, which is really big especially considering that you can only line up 109 Earths across the face of the Sun. The SDO is part of NASA’s Heliophysics System Observatory, or HSO, which studies the dynamics of our Solar System and helps predict space weather.

Space Weather
Our star–the Sun–is a bubbling, boiling ball of fire. It constantly belches out great clouds of hot gas. This gas is all charged up with electricity and travels at astounding speeds, some of it right toward Earth! This means that Earth’s weather happens inside the Sun’s weather!

Thank goodness Earth’s magnetic field and atmosphere protect us from most of this blast. Otherwise, the Sun’s weather would be OUR weather. Yikes!

However, we are still affected by the Sun’s atmosphere and its violent activities. We call this part of our weather "space weather," because it comes to us through space from the Sun.

D) The Sun’s Impact on Earth

Effect on communication
Solar flares cause eruptions of gas and energy near the Sun’s surface. They often are linked to sunspots. When solar flares erupt, they release an enourmous amount of energy!

Because they are so powerful, these flares can cause satellites orbiting the Earth to malfunction and could disrupt electricity to our cities and towns.

Before we had phones and televisions, a very powerful solar flare erupted in 1859. Called the “Carrington Event,” a cloud of energetic gas struch Earth squarely. If such an event happened today, it would fry computers, cell phones, new cars and would probably melt major transformers that help deliver electicity to our homes, schools, and businesses. Fortunately, NASA’s Living with a Star Program is studying the Sun and how its solar flares can affect the Earth. With the help of NASA missions, we should be able to have a pretty good idea of what our ever-changing Sun has in store for us.

Aurora borealis
There is another effect of the Sun on Earth when energetic gas from the Sun runs into Earth’s magnetic field. When this happens, impressive and beautiful light shows occur over the North and South Poles. These are known as the Northern and Southern lights. In the northern hemisphere, these lights are commonly known as the Aurora Borealis. This phenomenon is truly one of those spectacles of beauty in nature that you have to see it to believe it!

So as you can see, the International Space Station is a very important spacecraft finding new ways to improve our lives on Earth and helping us build a better future in space.

E) Solar Eclipses

What is an eclipse of the Sun?
One of the sky’s most spectacular events is a solar eclipse. A solar eclipse happens when the Moon passes in front of the Sun and blocks most of the Sun’s light from the Earth. When the Moon passes in front of the Sun, it naturally casts a shadow. As the eclipse continues and the Moon blocks more and more of the Sun, the sky gets darker and darker until it is dark outside even if it is daytime. The temperature outside also gets cooler. It is dangerous to look at a solar eclipse directly, even if you wear sunglasses. One safe way to view a solar eclipse is using a pinhole projector.

What causes solar eclipses and why?
There are three different kinds of solar eclipses. The most amazing is a total solar eclipse, which happens when the Moon completely blocks the face of the Sun. A partial solar eclipse happens when the Moon passes in front of the Sun, but does not hide it completely from view. It looks like someone took a big bite out of the Sun. The third type of solar eclipse is called an annular eclipse. This eclipses happen when the Moon passes directly in front of the Sun but, because of the Moon’s distance from Earth, the Sun is not completely hidden. During an annular eclipse, a small ring of the Sun’s surface will still be visible around the Moon.

The Moon’s Shadow
During an eclipse, we see two general parts of the Moon’s shadow. The lighter part of the shadow is called the penumbra. If the eclipse is a total eclipse, the darkest part of the shadow is called the umbra. If you are ever lucky enough to be in the path of the darkest part of the eclipse, also called the totality, you will first see the sky gradually get darker and darker until it is completely dark. When this happens, you are actually standing in the path of the shadow.

Before we knew about eclipses, some cultures believed that dragons or demons attacked the Sun whenever these events happened. Now we know better and needn’t be afraid. Instead, we think solar eclipses are pretty cool! People have studied the Sun for thousands of years and are still learning more about it every day. Since 1959, many space missions have observed and studied the Sun. These missions have studied many topics including solar winds and sunspots. This information has given us a better understanding of the Sun and how it affects us as we continue to learn more about our fascinating Sun and Solar System.

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