Seven Wonders of the Sun and Other Stars

Seven Wonders of the Sun and Other Stars — page 7 — The Extreme Ultraviolet Imaging Telescope took this picture of the Sun The telescope is on board the Solar and Heliospheric Observatory SOHO a spacecraft that orbits the Sun OUR AMAZING SUN The Sun measures about 860,000 miles 1,384,000 kilometers across That’s one hundred times wider than Earth If the Sun were hollow more than one million planets the size of Earth would ﬁt inside it The Sun is extremely heavy too It is about six hundred times heavier than all the planets in our solar system put together Like most other stars the Sun is a huge ball of hot burning gases The surface of the Sun burns at about 10,000 F 5,537 C The core or center of the Sun is even hotter The core burns at about 27 million F 15 million C 10

Seven Wonders of the Sun and Other Stars — page 8 — The Sun is vital to life because its light makes plants grow When you eat a plant a carrot a banana a slice of bread you are eating the product of sunlight Ken Croswell U S astronomer 2007 The Sun’s core is like a giant furnace Inside this furnace hydrogen turns into helium This change is called a nuclear reaction Nuclear reactions release huge amounts of energy The energy boils up from the core all the way to the Sun’s surface Like Earth the Sun has an atmosphere a layer of gases surrounding its surface The outermost layer of the Sun’s atmosphere is called the corona which means crown The corona looks a little like a halo or crown of light around the Sun From the corona the energy created in the Sun’s core ﬂows into space The Sun releases this energy in two main ways First the Sun sends out waves of radiation These waves include the sunlight we can see and the warm rays of heat we can feel Second the Sun sends out tiny electrically charged particles The constant stream of radiation and particles from the Sun is called the solar wind This wind from the Sun is very different from any wind on Earth As the solar wind ﬂows out toward Earth and far beyond it carries the light heat and other energy of the Sun The Sun’s light and heat are vitally important to our planet Without sunlight there would be no life on Earth Green plants could not grow Animals and people would have nothing to eat And Earth itself would be a frozen lifeless world SUNSPOTS Like Earth the Sun rotates or spins around The areas near the equator the widest part of the Sun spin faster than its north and south poles Also like Earth the Sun has a magnetic ﬁeld The magnetic ﬁeld is made up of invisible ﬁeld lines They run between the Sun’s north and south poles At the equator where the Sun rotates fastest these lines get stretched out This stretching tangles up the magnetic ﬁeld lines like an old garden hose or a twisted computer cord Solar Storms 11

Seven Wonders of the Sun and Other Stars — page 9 — THE SUN’S MAGNETIC FIELD north pole Sun’s rotation north pole north pole Equator magnetic field lines south pole south pole south pole The Sun’s untwisted magnetic field Over time the Sun’s rotation distorts the magnetic field These tangled areas are where sunspots often occur A sunspot is a dark circular area on the Sun’s surface The magnetic ﬁeld of a sunspot can be up to four thousand times stronger than Earth’s magnetic ﬁeld The strong magnetic ﬁelds in sunspots block the burning gases rising from the Sun’s core That’s why the sunspots are cooler and darker than the rest of the Sun’s surface Seven Wonders of the Sun and Other Stars SOLAR FLARES Sunspots often appear in pairs or groups Magnetic ﬁeld lines rise up from one sunspot and loop down into another These lines too can get tangled Tension builds up and up until 12 Sunspots are the black spots on this photo of the Sun They group together along magnetic ﬁeld lines

Seven Wonders of the Sun and Other Stars — page 10 — SPOTTING Sunspots An Italian astronomer named Galileo Galilei 1564 1642 studied the Sun He used his homemade telescope to see the Sun more closely As he watched he noticed some dark spots on the Sun’s face Galileo had discovered sunspots After Galileo no one learned much more about sunspots for hundreds of years Then in the early 1900s U S astronomer George Ellery Hale below began studying the Sun In 1908 Hale found that sunspots have powerful magnetic ﬁelds His discovery was a big breakthrough for scientists Before Hale made his discovery people thought that only Earth had magnetic ﬁelds ﬁnally something snaps This sudden release of energy results in a huge explosion a solar ﬂare Solar ﬂares can extend many thousands of miles into space They can last from a few seconds to several hours Flares release an amazing amount of energy Sunspots occur in twenty-two year cycles Each cycle starts slowly Gradually more and more sunspots pop up As the cycle moves toward its peak solar ﬂares and other solar storms break out The buildup reaches a peak after about eleven years After the peak the activity gradually slows down over another eleven years STORMY WEATHER ON THE SUN Scientists call the stormy activity on the Sun its weather When the sunspot cycle is at its height the Sun’s weather is usually most severe Solar ﬂares are the shortest and the most violent of any stormy weather on the Sun But other solar storms are powerful too Solar prominences and coronal mass ejections are two other kinds of solar storms A solar prominence happens when a dense tongue of gas loops out from the surface of the Sun It arches high into the corona Prominences Solar Storms 13

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