The Sun And Stars

1. The Sun And Stars McKenzie Brown and Kayla Walthall

2. The Sun formed over four and a half billion years ago! It originally came from clouds of dust and gas in space and gravity pulled the clouds together, gaining mass, with the most in the middle, least on the outer sides. Once it had enough mass, the mass in the middle sparked and then ignitedinto the Sun. The Sun’s diameter is about 87,000 mi wide. It is 110 times bigger than the Earth, and is 333,000 times heavier. How was the Sun created?How Big is the sun?

3. If you could take the Sun apart, and stack up its various elements, you would find that the Sun is made of hydrogen (74%) and helium (about 24%). Astronomers consider anything heavier than helium to be a metal. The remaining amount of the Sun is made of iron, nickel, oxygen, silicon, sulfur, magnesium, carbon, neon, calcium and chromium. In fact, the Sun is 1% oxygen; and everything else comes out of that last 1%. What is the sun made of?

4. How is the sun? • At the core of the sun, gravitational attraction produces immense pressure and temperature, which can reach more than 27 million degrees F (15 million degrees C). Hydrogen atoms get compressed and fuse together, creating helium. This process is called nuclear fusion. • Nuclear fusion produces huge amounts of energy. The energy radiates outward to the sun's surface, atmosphere and beyond. From the core, energy moves to the radiative zone, where it bounces around for up to 1 million years before moving up to the convective zone, the upper layer of the sun's interior. The temperature here drops below 3.5 million degrees F (2 million degrees C). Large bubbles of hot plasma form a soup of ionized atoms and move upwards to the photosphere. The temperature in the photosphere is about 10,000 degrees F (5,500 degrees C). It is here that the sun's radiation is detected as sunlight. Sunspots on the photosphere are cooler and darker than the surrounding area. At the center of big sunspots the temperature can be as low as 7,300 degrees F (4,000 degrees C). • The chromosphere, the next layer of the sun's atmosphere is a bit cooler — about  7,800 degrees F (4,320 degrees C). Visible light from the chromosphere is usually too weak to be seen against the brighter photosphere, but during total solar eclipses, when the moon covers the photosphere, the chromosphere can be seen as a red rim around the sun. • Temperatures rise dramatically in the corona, which can also only be seen during an eclipse as plasma streams outward like points on a crown. The corona can get about 3.5 million degrees F (2 million degrees C). As the corona cools, losing heat and radiation, matter is blown off as the solar wind.

5. Yes of course, the sun gives us sun burns, makes the sidewalk hot to burn our feet, and melts our ice-cream, but have you ever thought of how much the sun helps us? The sun provides warmth to all living organisms down on earth, and also gives light to all plants to help them grow and produce oxygen. Without the sun nothing would be able to survive. So next time your at the beach or even in your backyard when the sun gives you a sunburn or melts your ice-cream, don’t be mad because the sun is actually helping you no matter how bad you wanted to eat that ice-cream. WHAT DOES THE SUN DO?

6. FUN FACTS ABOUT THE SUN • The Sun is one among the 200 billion stars in our Milky Way galaxy. • The Sun is one among the 6000 stars, which is visible to naked eye from the Earth. • The mass of Sun is  1.989 x 1030 kg (Approximately 2 million trillion trillionkilograms). • Each second the Sun loses 5 million tons of material. • If a drop sized matter from the core of the Sun is placed on the surface of the Earth, no living organism will survive for a distance of 150 km from that drop. • The volume of Sun is equivalent to the volume of 1.3 million earths. • A man weighing 60 kg in the Earth will weigh 1680 kg in the Sun. • The Sun's gravitational pull is so strong that, even Pluto, a planet 5.9 billion kilometer away from Sun, is kept in it's orbit. • The Sun orbits around the center of our Milky Way galaxy once every 240 million years. • The Sun has circledthe Milky Way galaxy for about 20 times only since it's formation. • Solar flares are violent explosions taking place in the Sun's atmosphere occasionally. Solar flares can reach more than 100,000 miles away from the sun. • The luminosity of the Sun is equivalent to the luminosity of 4 trillion trillion light bulbs of 100 watt

7. STARS

8. We can only see a few thousand stars at most with our naked eyes. These are a mixture of stars which are nearby, and bright stars which are further away; but they are only a tiny fraction of the 100,000,000,000 stars in our own galaxy. We can't see stars in other galaxies without powerful telescopes. In fact the entire brightest neighboring galaxy (M31, the Andromeda galaxy), which contains more stars than our own, is only as bright as an average star visible to the unaided eye. How many stars are in our galaxy?

9. The Constellations are totally imaginary things that poets, farmers and astronomers have made up over the past 6,000 years (and probably even more!). The real purpose for the constellations is to help us tell which stars are which, nothing more. On a really dark night, you can see about 1000 to 1500 stars. Trying to tell which is which is hard. The constellations help by breaking up the sky into more managable bits. They are used as mnemonics, or memory aids. For example, if you spot three bright stars in a row in the winter evening, you might realize, "Oh! That's part of Orion!" Suddenly, the rest of the constellation falls into place and you can declare: "There's Betelgeuse in Orion's left shoulder and Rigel is his foot." And once you recognize Orion, you can remember that Orion's Hunting Dogs are always nearby. Then you might recognize the two bright stars in the upper and lower left of the photograph as Procyon in Canis Minor and Sirius in Canis Major, respectively. Where did the constellations come from? OK, so we know the constellations are helpful for remembering the stars, but why would people want to do that (besides astronomers, that is)? After all, I said at the beginning that farmers  invented the constellations. Why did they do that? Was it for some religious purpose? Yes and no. Around the world, farmers know that for most crops, you plant in the spring and harvest in the fall. But in some regions, there is not much differentiation between the seasons. Since different constellations are visible at different times of the year, you can use them to tell what month it is. For example, Scorpius is only visible in the northern hemisphere's evening sky in the summer. Some historians suspect that many of the myths associated with the constellations were invented to help the farmers remember them. When they saw certain constellations, they would know it was time to begin the planting or the reaping. What are constellations?

10. Different types of stars • When we think of stars we usually imagine our Sun. But the simple fact is that the Universeis made up of many different types of stars. In fact looking into the heavens most stars look very different, and some aren't really stars at all. So here is a run down of the most common types of stars in the galaxy. • A star is said to be born once nuclear fusion commences in its core. At this point it is, regardless of mass, considered a main sequence star. This is where the majority of a star's life is lived. Our Sun has been on the main sequence for about 5 billion years, and will persist for another 5 billion years or so before it transitions to become a Red Giant Star. • Once a star has used up all of its hydrogen fuel in its core it transitions off the main sequence and becomes a red giant. Depending on the mass of the star it can oscillate between various states before ultimately becoming either a white dwarf, neutron star or black hole. One of our nearest neighbors (galactically speaking), Betlegeuse is currently in its red giant phase and is expected to go supernovaat any time. • When low-mass stars, like our Sun, reach the end of their lives they enter the red giant phase. But the outward radiation pressure overwhelms the gravitational pressure and the star expands farther and farther out into space. Eventually, the outer envelope of the star begins to merge with interstellar space and all that is left behind is the remnant of the star's core. This core is a smoldering ball of carbon and other various elements that glows as it cools. While often referred to as a star, a white dwarf is not technically a star as it does not undergo nuclear fusion. Rather it is a stellar remnant, like a black hole or neutron star. Eventually it is this type of object that will be the sole remains of our Sun billions of years from now.

11. Types of stars…continued • A neutron star, like a white dwarf or black hole, is actually not a star but a stellar remnant. When a massive star reaches the end of its life it undergoes a supernova explosion, leaving behind its incredibly dense core. A soup-can full of neutron star material would have about the same mass as our Moon. There only objects known to exist in the Universe that have greater density are black holes. • Black holes are the result of very massive stars collapsing in on themselves due to the massive gravity they create. When the star reaches the end of its main sequence life cycle, the ensuing supernova drives the outer part of the star outward, leaving only the core behind. The core will have become so dense that not even light can escape its grasp. These objects are so exotic that the laws of physics break down • Brown Dwarfs are not actually stars, but rather "failed" stars. They form in the same manner as normal stars, however they never quite accumulate enough mass to ignite nuclear fusion in their cores. Therefore they are noticeably smaller than main sequence stars. In fact those that have been detected are more similar to the planet Jupiter in size, though much more massive (and hence much denser). • Most stars we see in the night sky maintain a constant brightness (the twinkling we sometimes see is actually an atmospheric effect and not a variation of the star), but some stars actually do vary. While some stars owe their variation to their rotation (like rotating neutron stars, called pulsars) most variable stars change brightness because of their continual expansion and contraction. The period of pulsation observed is directly proportional to its intrinsic brightness. For this reason, variable stars are used to measure distances since their period and apparent brightness (how bright they appear to us on Earth) can be sued to calculate how far away they are from us.

12. Questions • What is the center of the sun called? • How was the sun formed? • Name one thing the sun does for us. • What are constellations? • Name one type of star.