Understanding Our Sun

Understanding Our Sun — page 3 — The All Important Sun All life on Earth exists because of the Sun The Sun gives out energy in the form of light and heat This energy supports all life on Earth It warms the oceans and the atmosphere Green plants convert sunlight into food for themselves and for animals The Sun's gravity also holds Earth in its regular orbit If Earth drifted out of its orbit and off into space the planet would become bitterly cold and all life would end As gas and dust clumped together at the center of this cloud it formed a star As the star attracted more material its gravity grew stronger This gravity made the cloud around it spin More clumps of matter became planets and dwarf planets They were made from the same materials as the Sun itself The Sun generates a huge amount of energy and magnetism Magnetism is a force that attracts or repels other objects The Sun's magnetism forms the heliosheath This is a magnetic field that extends beyond our Solar System This acts as a shield to protect our Solar System from harmful cosmic radiation from deep space The Center of It All More than 4 6 billion years ago our Solar System did not yet exist There was nothing but a cloud of gas and dust This interstellar dust occurs throughout our galaxy The Sun's magnetic field may protect our whole Solar System as it orbits the center of the Milky Way Galaxy Saturn Uranus Neptune 6 Sun Mercury Venus Earth Mars Jupiter

Understanding Our Sun — page 4 — About 10 percent of the stars in our Milky Way galaxy are yellow dwarfs like our Sun Dwarfs and Giants The Sun is a G-type main sequence star also known as a yellow dwarf This is a type of star that is a little more than a million times larger than Earth More than 70 percent of the Sun is made up of hydrogen which acts as the fuel for the star Most of the rest is helium with small amounts of other elements Yellow dwarfs can keep burning their hydrogen for up to 10 billion years Many stars in the universe are bigger and burn brighter than yellow dwarfs These stars called giants supergiants and hypergiants only last for a few million years before they run out of fuel Other stars called red dwarfs last much longer but do not burn as brightly By providing a lot of energy but also burning for billions of years the Sun may be an ideal star for supporting life on the planets that orbit around it 7

Understanding Our Sun — page 5 — Solar flares erupting from the Sun’s surface are up to 35 times the diameter of Earth Why Study the Sun It is difficult to study the Sun It shines so brightly it can blind anyone who looks directly at it Astronomers use special filters to protect their eyes from harmful light They also study the Sun using instruments to detect invisible radiation such as X-rays This has allowed them to understand a lot more about the Sun They have figured out that Earth is lucky to be in a part of our Solar System called the Goldilocks Zone This means that Earth is not so far from the Sun that we freeze and not so close that the Sun makes it too hot for anything to live The Power of the Sun Earth and everyone on it depends on the Sun It has existed longer than Earth and it is easy to assume that it will always be there In fact the Sun is a huge explosion that has been burning for more than 4 6 billion years Eventually it will run out of fuel and die Every second Earth receives enough energy from the Sun to light 17 4 quadrillion lightbulbs a quadrillion is a 1 followed by 15 zeros A small backyard receives enough solar energy to power 10 houses for the whole day 8

Understanding Our Sun — page 6 — Only about 1 billionth of the energy the Sun releases reaches Earth The way the Sun releases its energy is inconsistent Sunspots solar flares and changes within the Sun can unleash coronal mass ejections CMEs which are jets of energy If these charged particles hit Earth they could destroy electricity grids The power system could be out for years A Need to Know Astronomers observe the Sun closely through special telescopes and solar observatories on Earth and in space Not only does studying the Sun tell us more about the other stars in the sky but it can also help predict future changes in the Sun’s behavior This might allow us to be better prepared for whatever our nearest star throws at us MISSION Space Science The Solar and Heliospheric Observatory SOHO is a satellite launched in 1995 by the National Aeronautics and Space Agency NASA and the European Space Agency ESA NASA almost lost the satellite due to problems with its navigation system but was able to recover the ship Since then SOHO has helped scientists observe how the Sun has changed over 20 years and discovered more than 3,000 comets SOHO weighs 1,345 pounds 610 kg It carries 12 different instruments that look at the Sun in a range of ways 9

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