Is the sun dying?

Without sun's existence, there wouldn't be life on Earth. In the grand scheme of things, however, our sun is simply another star among star among the other hundreds of billions of stars in the universe.Officially, the Sun is a class G2V star- in other words,a main-sequence yellow dwarf have a temperature range of 5,000 to 6,000 degrees Celsius and their mass is about 80-120 percent of the mass of the sun. That means that the Sun is one of the biggest yellow dwarfs in the group.

Like other yellow dwarfs, the Sun converts hydrogen to helium in its core through nuclear fusion,which generates massive amounts of energy and light.The Sun fuses about 620 million metric tons (683 million short tons) of hydrogen per sec. Based on the speed, astronomers believes that the sun is about halfway through its life cycle. About 40 percent of the hydrogen has been converted,leaving another 3 to 5 billion years before the Sun evolves into the next stage in its life cycle:a red giant.

 

But let's start at the beginning.The Sun formed approximately 4-5 billion years ago, at the same time as the rest of the solar system. At this time a spinning molecular cloud of dust, hydrogen and helium flattened out into a disk, With a gaseous sphere at its center that contained most of the mass.This sphere had a gravitational pull that attracted dust and other materials from the disk,which caused the sphere to compress until it begin converting the hydrogen to helium.A star-in this case, Our Sun-was born.

The Sun can't keep fusing hydrogen indefinitely, though - there's a finite supply. Nuclear fusion occurs in the Sun's core due to gravitational pressure, which heats the core to 15 million degrees (27 million degrees  Fahrenheit) and splits the hydrogen atoms.There's dedicates balance,known as 'hydrostatic' equilibrium 'between the inward compression exerted by gravity and the outward pressure from the energy created by nuclear reaction.As the Sun's hydrogen supply is used up,the nuclear fusion in its core will decrease, and the core will contract. The core will heat up to a temperature of 100 billion degrees Celsius and begin fusing helium into carbon.The outer layers of the Sun will expand as it become a red giant.This means that the Sun's radius will be 250 times larger than its current radius,and it will swallow the Earth.

       Astronomers once thought that because the Sun's gravitational pull will weaken when it becomes a red giant, the associated planetary movement outwards away from the Sun might spare our planet. However, the most recent projections show that Earth would likely still be in the outer layer of Sun,where it will be pulled in and vaporized.Even if the Earth itself is spared,astronomers still believe that the increasing heat from the Sun will eliminate life on Earth about one billion years from now.

Source - How it Works Book and Internet

What are Saturn’s Rings Made Of?

Saturn's rings are made of billions of pieces of ice, dust and rocks. Some of these particles are as small as a grain of salt, while others are as big as houses. These chucks of rock and ice are thought to be pieces of comets, asteroids or even moons which were torn apart by the strong gravity of Saturn before they could reach the planet.

Galileo Galilei was the first to observe the rings of Saturn in 1610 using his telescope, but was unable to identify them as such.

Ring theory and observations

In 1655, Christiaan Huygens became the first person to suggest that Saturn was surrounded by a ring. Using a 50 power refracting telescope that he designed himself, far superior to those available to Galileo, Huygens observed Saturn and wrote that "It [Saturn] is surrounded by a thin, flat, ring, nowhere touching, inclined to the ecliptic" Robert Hooke was another early observer of the rings of Saturn, and noted the casting of shadows on the rings. 

In 1675, Giovanni Domenico Cassini determined that Saturn's ring was composed of multiple smaller rings with gaps between them; the largest of these gaps was later named the Cassini Division. This division is a 4,800 km-wide region between the A Ring and B Ring.

In 1787, Pierre-Simon Laplace suggested that the rings were composed of a large number of solid ringlets.

In 1859, James Clerk Maxwell demonstrated that the rings could not be solid or they would become unstable and break apart. He proposed that the rings must be composed of numerous small particles, all independently orbiting Saturn. Maxwell's theory was proven correct in 1895 through spectroscopic studies of the rings carried out by James Keeler of Allegheny Observatory.

The rings are named alphabetically in the order they were discovered. The main rings are, working outward from the planet, C, B and A, with the Cassini Division, the largest gap, separating Rings B and A. Several fainter rings were discovered more recently. The D Ring is exceedingly faint and closest to the planet. The narrow F Ring is just outside the A Ring. Beyond that are two far fainter rings named G and E. The rings show a tremendous amount of structure on all scales, some related to perturbations by Saturn's moons, but much unexplained.






Saturn is sometimes called the ”Jewel of the Solar System” because its ring system looks like a crown. The rings are well known, but often the question ”what are Saturn’s rings made of” arises. Those rings are made up of dust, rock, and ice accumulated from passing comets, meteorite impacts on Saturn’s moons, and the planet’s gravity pulling material from the moons. Some of the material in the ring system are as small as grains of sand, others are larger than tall buildings, while a few are up to a kilometer across. Deepening the mystery about the moons is the fact that each ring orbits at a different speed around the planet. 
 
Saturn is not the only planet with a ring system. All of the gas giants have rings, in fact. Saturn’s rings stand out because they are the largest and most vivid. The rings have a thickness of up to one kilometer and they span up to 482,000 km from the center of the planet.

Below is a list of the main rings and gaps between them along with distances from the center of the planet and their widths.

To view Image Right Click on Image and Select View Image

• The D ring is closest to the planet. It is at a distance of 66,970 – 74,490 km and has a width of 7,500 km.
• C ring is at a distance of 74,490 – 91,980 km and has a width of 17,500 km.
• Columbo Gap is at a distance of 77,800 km and has a width of 100 km.
• Maxwell Gap is at a distance of 87,500 km and has a width of 270 km.
• Bond Gap is at a distance of 88,690 – 88,720 km and has a width of 30 km.
• Dawes Gap is at a distance of 90,200 – 90,220 km and has a width 20 km.
• B ring is at a distance of 91,980 – 117,580 km with a width: 25,500 km.
• The Cassini Division sits at a distance of 117,500 – 122,050 km and has a width of 4,700 km.
• Huygens gap starts at 117,680 km and has a width of 285 km – 440 km.
• The Herschel Gap is at a distance of 118,183 – 118,285 km with a width of 102 km.
• Russell Gap is at a distance of 118,597 – 118,630 km and has a width of 33 km.
• Jeffreys Gap sits at a distance of 118,931 – 118,969 km with a width of 38 km.
• Kuiper Gap ranges from 119,403 -119,406 km giving it a width of 3 km.
• Leplace Gap is at a distance of 119,848 – 120,086 km and a width of 238 km.
• Bessel Gap is at 120,305 – 120,318 km with a width of 10 km.
• Barnard Gap is at a distance of 120,305 – 120,318 km giving it a width of 3 km.
• A ring is at a distance of 122,050 – 136,770 km with a width of 14,600 km.
• Encke Gap sits between 133,570-133,895 km for a width of 325 km.
• Keeler Gap is at a distance of 136,530-136,565 km with a width of 35 km.
• The Roche Division is at 136,770 – 139,380 km for a width 2600 km.
• F ring is begins at 140,224 km, but debate remains as to whether it is 30 or 500 km in width.
• G ring is between 166,000 – 174,000 km and has a width of 8,000 km.
• Finally, we get to the E ring. It is between 180,000 – 480,000 km giving it a width of 300,000 km.

As you can see, a great deal of observation has been dedicated to understanding and defining Saturn’s rings. Hopefully, having the answer to ”what are Saturn’s rings made of” will inspire you to look more deeply into the topic.

How the Seasons Work?

It turns out that the elliptical orbit of the Earth has little effect on the seasons. Instead, it is the 23.45-degree tilt of the planet's rotational axis that causes us to have winter and summer.
The diagram below demonstrates what happens.

In this diagram, you can see the axis of rotation and the equator. The Northern Hemisphere (at the top) is currently experiencing winter, and the Southern Hemisphere is experiencing summer. By looking at how sunlight is landing on the planet in the diagram, you can clearly see two things:

• The Southern Hemisphere is getting about three times as much sunlight as the Northern Hemisphere.
• The North Pole is getting zero sunlight, which is why it experiences 24 hours of darkness in January.

That huge difference in the amount of sunlight reaching the ground in the different hemispheres is what causes the seasons.

How do orbits work?

We might take it for granted, but why do stars, moons, planets or any celestial bodies constantly move around one another?

 What an Orbit Really Is

The drawings at the right simplify the physics of orbiting Earth. We see Earth with a huge, tall mountain rising from it. The mountain, as Isaac Newton first envisioned, has a cannon at the top. When the cannon is fired, the cannonball follows its ballistic arc, falling as a result of Earth's gravity, and it hits Earth some distance away from the mountain. If we put more gunpowder in the cannon, the next time it's fired, the cannonball goes halfway around the planet before it hits the ground. With still more gunpowder, the cannonball goes so far that it never touches down at all. It falls completely around Earth. It has achieved orbit.
If you were riding along with the cannonball, you would feel as if you were falling. The condition is called free fall. You'd find yourself falling at the same rate as the cannonball, which would appear to be floating there (falling) beside you. You'd never hit the ground. Notice that the cannonball has not escaped Earth's gravity, which is very much present -- it is causing the mass to fall. It just happens to be balanced out by the speed provided by the cannon.   

How do orbits work?

Although we don’t encounter orbits day to day, it’s common knowledge that in space, satellites, asteroids, moons, planets and even stars move around other celestial bodies in a seemingly perpetual dance. With the right conditions, anything will fall into orbit around Earth. But what are those conditions?

A terrestrial orbit is actually a freefall along the curve of the Earth’s gravity that never touches down. The basic physics is the same for any planet or star, no matter its size. For an Earth-like planet, if an object is at the right altitude so that the thinner atmosphere doesn’t drag too much – around 160 kilometres (99 miles) up – and the acceleration is enough – about 28,080 kilometres (17,450 miles) per hour – it will continue to tumble around the planet.

To put a satellite or shuttle into a circular ‘high’ orbit, the craft makes use of boosters to go from low orbit into a transfer orbit to achieve the required height, technically known as its apogee. Left to its own devices, the spacecraft would fall into an elliptical orbit, so an additional rocket motor called an ‘apogee kick’ (AKM) fires at the appropriate point. This gives the vessel the extra boost it needs to remain at that specific altitude in a high orbit.

When does sky become space?

The Kármán line (Karman line) is an official boundary between the Earth’s atmosphere and space, lying 100km (approximately 62 miles) above sea level. The governing body for air sports and aeronautical world records, Federation Aeronautique Internationale (FAI), recognizes it as the Line where aeronautics ends and astronautics begins.   

The line was named after Theodore von Kármán, (1881–1963) a Hungarian-American engineer and physicist who was active primarily in the fields of aeronautics and astronautics. He first calculated that around this altitude the Earth's atmosphere becomes too thin for aeronautical purposes (because any vehicle at this altitude would have to travel faster than orbital velocity in order to derive sufficient aerodynamic lift from the atmosphere to support itself, neglecting centrifugal force). There is an abrupt increase in atmospheric temperature and interaction with solar radiation just below the line, which places the line within the greater thermosphere.

Thin air also explains why the Earth‘s sky looks blue and space is black. Atmospheric gases scatter blue light more than other colours, turning the sky blue. At higher altitudes, less air exists to scatter light.

Some people (including the FAI in some of their publications) also use the expression "edge of space" to refer to a region below the conventional 100 km boundary to space, which is often meant to include substantially lower regions as well. Thus, certain balloon or airplane flights might be described as "reaching the edge of space". In such statements, "reaching the edge of space" merely refers to going higher than average aeronautical vehicles commonly would.

Astronomy - July 2013

The world's best-selling astronomy magazine offers you the most exciting, visually stunning, and timely coverage of the heavens above. Each monthly issue includes expert science reporting, vivid color photography, complete sky coverage, spot-on observing tips, informative telescope reviews, and much more! All this in an easy-to-understand, user-friendly style that's perfect for astronomers at any level.

• Hardcover: 80 pages
• File size: 27.2 MB   |  File Format: PDF

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Hardcover: 1622 pages

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Hardcover: 1622 pagesFile Size: 45.0 Mb | File Format: PDF

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Physics for Scientists and Engineers with Modern Physics (9th Ed)

Book Details:

• Hardcover: 1622 pages
• Publisher: Cengage Learning; 9 edition (January 17, 2013)
• Language: English
• ISBN-10: 1133954057
• ISBN-13: 978-1133954057
• File Size: 45.0 Mb | File Format: PDF

Book Description:
Achieve success in your physics course by making the most of what PHYSICS FOR SCIENTISTS AND ENGINEERS WITH MODERN PHYSICS has to offer. From a host of in-text features to a range of outstanding technology resources, you’ll have everything you need to understand the natural forces and principles of physics. Throughout every chapter, the authors have built in a wide range of examples, exercises, and illustrations that will help you understand the laws of physics AND succeed in your course!

Table of Contents

Part 1: Mechanics

Ch 1: Physics and Measurement
Ch 2: Motion in One Dimension
Ch 3: Vectors
Ch 4: Motion in Two Dimensions
Ch 5: The Laws of Motion
Ch 6: Circular Motion and Other Applications of Newton’s Laws
Ch 7: Energy of a System
Ch 8: Conservation of Energy
Ch 9: Linear Momentum and Collisions
Ch 10: Rotation of a Rigid Object About a Fixed Axis
Ch 11: Angular Momentum
Ch 12: Static Equilibrium and Elasticity
Ch 13: Universal Gravitation
Ch 14: Fluid Mechanics

Part 2: Oscillations and Mechanical Waves

Ch 15: Oscillatory Motion
Ch 16: Wave Motion
Ch 17: Sound Waves
Ch 18: Superposition and Standing Waves

Part 3: Thermodynamics

Ch 19: Temperature
Ch 20: The First Law of Thermodynamics
Ch 21: The Kinetic Theory of Gases
Ch 22: Heat Engines, Entropy, and the Second Law of Thermodynamics

Part 4: Electricity and Magnetism

Ch 23: Electric Fields
Ch 24: Gauss’s Law
Ch 25: Electric Potential
Ch 26: Capacitance and Dielectrics
Ch 27: Current and Resistance
Ch 28: Direct-Current Circuits
Ch 29: Magnetic Fields
Ch 30: Sources of the Magnetic Field
Ch 31: Faraday’s Law
Ch 32: Inductance
Ch 33: Alternating-Current Circuits
Ch 34: Electromagnetic Waves

Part 5: Light and Optics

Ch 35: The Nature of Light and the Principles of Ray Optics
Ch 36: Image Formation
Ch 37: Wave Optics
Ch 38: Diffraction Patterns and Polarization

Part 6: Modern Physics

Ch 39: Relativity
Ch 40: Introduction to Quantum Physics
Ch 41: Quantum Mechanics
Ch 42: Atomic Physics
Ch 43: Molecules and Solids
Ch 44: Nuclear Structure
Ch 45: Applications of Nuclear Physics
Ch 46: Particle Physics and Cosmology

Time,Space,Stars and Man-The Story of the Big Bang

• Hardcover: 496 pages
• Publisher: World Scientific Publishing Company (April 2009)
• Language: English
• ISBN-10: 1848162723
• ISBN-13: 978-1848162723

Most well-read, but non-scientific, people will have heard of the term 'Big Bang' as a description of the origin of the Universe. They will recognize that DNA identifies individuals and will know that the origin of life is one of the great unsolved scientific mysteries. This book brings together all of that material. Starting with the creation of space and time - known as the Big Bang - the book traces causally related steps through the formation of matter, of stars and planets, the Earth itself, the evolution of the Earth's surface and atmosphere, and then through to the beginnings of life and the evolution of man. The material is presented in such a way that an intelligent non-scientist can comprehend it, without using formulae or equations but still preserving the integrity of the involved science.This book does not solve the mysteries of what initiated the Big Bang or how life evolved from inanimate matter, but it does make clear the nature of those problems. The reader will be left with a sense of wonderment that he or she actually exists!