I'm glad you are here. I've made these notes for you to read while I'm presenting, and I've tried to say only what is most important. If you want to learn more, please use your interpreter, if you have one, to communicate any questions, any time. Are you ready to learn about the fantastic story of our Sun? This story is about other stars in the sky too, and it's even about all of us. Look at this picture of our wonderful star, shining bright from Earth orbit! This photo was taken by the crew of the International Space station - from space. I hope we all appreciate how far we've come since Galileo first used a telescope in 1609 - only 400 years ago! Along the way, we've learned so much about the Universe, but we still wonder and ask questions. We ask questions. Like this one. What does this word make you think of? What is the first "thing" you think of? Hold on to that thought a minute. Like most people, you probably thought of something like the things you see pictured here. We usually think of nature as many different things on Earth. But nature, in a larger scale, is far more rich, diverse and full of beauty than just the Earth. Itʼs everything we see beyond the Earth too. But Iʼll bet you didnʼt think of something ASTRONOMICAL, did you? Like STARS. Look at how many there are in this picture! Even while visiting McDonald Observatory, we hardly ever think of stars as part of nature. But they are. ALL the stars in this picture are just SOME of the stars in our GALAXY of stars, called the Milky Way. Our Sun is one of hundreds of billions of other stars in our galaxy. Since Galileo, weʼve learned that the whole Universe contains hundreds of billions of other GALAXIES. Each one full of stars. You see, there are more stars than anything else in nature.
When we look down to Earth, we see life just forming, life flourishing in bloom, and life that has reached the end, leaving new life in its place. New beginnings. Just the same, when we look up to our galaxy above we see stars just forming, stars living out their incredibly long lives, and stars reaching their end, leaving behind material that will form new astronomical objects. New beginnings. Our sun, the Earth, and the Solar System formed from cosmic material left behind by stars of the past. Itʼs a cosmic cycle that the Earth, all life, and every star in every galaxy are part of. If you think our Galaxy of stars is beautiful to see from the inside, looking up, you should see what it looks like from the outside. If we could actually see it from the outside, it would look like this. This isn't a real photograph because no-one and nothing has ever traveled far enough outside our Galaxy to take a picture like this. Like a garden full of young sprouts, blooming flowers and aging plants, our Galaxy is full of stars at different stages of thier life. Do you see the red, Hydrogen rich clouds? Stars have formed there and shine for tens of millions or billions of years. But in this picture there are also stars reaching a peaceful, or sometimes violent end, leaving behind dark clouds of stellar remains. Those dark clouds mix with the red Hydrogen clouds, forming other objects. But where is the Sun in this picture? Which star is ours? Well, it's not in the center, if that's what you thought. We've shown you the location of the our Sun, right in the middle of the white circle. Do you see it? Remember, this isn't a real photograph. It's a model we are using to represent scientific observations of our Galaxy. The scale of this model is huge. Sunlight would need 10,000 years to traverse two concentric circles outward. That means that all the bright stars you see in the sky, outside at night, are STILL close enough to the sun to be located WITHIN the white circle. When we view our Galaxy from the outside, our wonderful star is lost among so many others. But it's so important to us. Our Sun is a basic, garden variety star among many, many others, made from a Hydrogen cloud seasoned with material of giant stars of the past. It's small to medium sized, middle aged, and closeby. Some stars are much hotter than our warm, 10.000 degree star. Knowing many things, like what atoms and thier abundancies make up the sun, it's mass, temperature, and where in the Galaxy it's located can tell us how old the sun is. We also know that stars are not all the same. They're not the same size, mass, tempurature or age. But they all form the same way.
This is a real picture of a star forming region called M42, a cloud of dense gas and dust also called the Orion Nebula. This cloud of gas and dust is just part of a huge, cooler and less dense molecular cloud. You see, when we let go of a ball, it falls down or towards the center of Earth. For the same reason, GRAVITY, dense pockets of cool gas and dust fall together to form this beautiful structure. The gas begins to rotate and fall inward, heating to enormous temperature and pressure in the core, and eventually becoming a star, emitting great energy. M42 will produce 1000ʼs of stars like the Sun in this way. But thatʼs not all that forms! Some of the nearby gas and tiny dust particles will NOT form with the star. Instead, static forces will start clinging them together, like the ones that make your socks cling to your sheets. Eventually gravitational forces will fuse larger pieces. Those new clumps of material become PLANETS, that continue to rotate around the star, or ORBIT the star. This is how systems of planets form around stars, and it happens all the time in our Galaxy. Did you know that Astronomers have confirmed nearly 800 planets that orbit OTHER stars? Astronomers have discovered 1000ʼs, but confirming them takes more observation. The Sun has layers of atmosphere that surrounds its super dense, gas core. The yellowishorange layer here is called the Photosphere and is 10,000 F. Galileo was one of the first people to notice that the Sun rotates. He noticed this the same way you can now. Do you see the dark sunspots? He simply watched as sunspots, like these, rotated in view, and then out of view. Why are they dark? You can watch me demonstrate that a faint light bulb filament appears dark when viewed against the brighter overhead projector. In the same way, sunspots are not as hot and bright as surrounding gas, so the cooler sunspots appear dark. Let me know demonstrate WHY the sunspots are cooler. Can you see the loop pattern made by the magnetic field that surrounds the magnet? Big sweeping, arched loops that extend from pole to pole, and extending away from the poles closer to the ends. You can see those same patterns surrounding the sunspot here. The magnetic field causes the gas temperature at the sunspot to drop, making it appear dark. When the magnetic field that cooled the gas weakens, the gas temperature rises again and the sunspot disappears.
The twisted and contorted magnetic field of the sun causes electrically charged gas to be carried up through the photosphere in big arching loops. The giant loop of super-heated gas that rises through the Photosphere is called a Solar Prominence. Prominences appear as fantastic wisps of gas that make beautiful patterns... - sometimes loop patterns......other times they appear as drifting sheets of gas flowing through the magnetic field, like a giant jelly fish gliding through the cosmic sea....watch for the loop Prominence!
Another fantastic feature caused by the Sunʼs magnetic field is called a Solar Flare. In this picture, the Flare is the bright region between the two sunspots. A Flare occurs when the magnetic field that caused the sunspots suddenly weakens and releases huge amounts of energy. Here is a strong magnetic field that has caused two sunspots. Watch the sudden release of energy! That burst of gas flows throughout the magnetic field lines, while some of the gas can break free from the sun and travel out into space. Here is more incredible footage of flares...and more. Truly amazing footage, thanks to the newly deployed Solar Dynamics Observatory - in space!
Coronal Mass Ejections are powerful eruptions from the sun. They are blasts of super-heated electrically charged gas, called plasma. Here is what they look like. Do you see the giant plume of gas radiating outwards? That is a Coronal Mass Ejection. The electrically charged gas can collide with the Earth, and be trapped by our magnetic field. This movie is from a telescope in space called SOHO. When that electrically charged gas, or plasma, is trapped in our magnetic field, it causes our atmosphere to illuminate in beautiful sheets, or ribbonʼs of light. We call this the Aurora Borealis, or Northern Lights. Do you remember the first picture I showed you of the sun, photographed by the Astronauts aboard the International Space Station? Look at this next picture... The Aurora Borealis photographed from the International Space Station! You donʼt normally hear Texans talking about Northern Lights, because Texas is too far south. But rarely, we CAN see Northern Lights in Texas.
Believe it or not, this movie of the Aurora Borealis WAS taken here, at the Visitors Center at McDonald Observatory! As in so much of nature, the sun goes through cycles. In this picture, Iʼm showing you how the sun goes through a Sunspot Cycle that is roughly 11 years. No star can last forever. Stars like our Sun have a lifetime of about 10 billion years. At the end of its life, our Sun will become a beautiful object called a Planetary Nebula. These are pictures of stars, like our sun, that have become a Planetary Nebula. Notice that each is a ring, bubble, or shell of gas. This is the material that made up the atmosphere of the star, and now has been expelled into space, expanding in beautiful patterns. All that remains of the star is the exposed core, in the center, called a white dwarf. The white dwarf is similar in size to our Earth, very hot, but not so easy to see because itʼs so small. To the left is a brown building, that has a roof that slides away, to expose the telescope you see on the right. Weʼre now going to use that telescope to explore the sun! Watch with me and see if you can find some of the features that you have studied with me today. Look for sunspots on the face of the sun, solar prominences along the edge of the sun, and finally, if weʼre lucky we might even see a flare!
Itʼs time to leave for our tour! Remember to bring your camera and jacket along with you! I hope you enjoyed the wonderful story of our sun! Thank you for participating with us, and I sincerely hope you enjoy the rest of your visit at the UT McDonald Observatory.