Eagle nebula discovered by Jean-Philippe de Cheseaux

The Eagle Nebula is a young open cluster of stars in the constellation Serpens, discovered by Jean-Philippe de Cheseaux in 1745-46. Its name derives from its shape that is thought to resemble an eagle.

• Location:  Constellation Serpens
• Distance to Earth: 6,500 light years
• Size: 9.5 light years 

What are the Pillars of Creation?

One of the best-known pictures of the Eagle Nebula is the Hubble Space Telescope image taken in 1995, highlighting the "Pillars of Creation." The three columns contain the materials for building new stars, and stretch four light-years out into space. Newborn stars outside of the famous Hubble image are responsible for sculpting the pillars, using ultraviolet light to burn away some of the gas within the clouds.

 In 2010, images of the pillars taken by NASA's Chandra X-ray Observatory peered inside the pillars to reveal only a handful of x-ray sources. Because new stars are supposed to be a hot bed of x-ray activity, scientists speculated that the star-forming days of the pillars were coming to an end.

What are EGGs?

Evaporating gaseous globules, or EGGs, are dense pockets of gas that lie at the top of the columns. Some EGGs appear as tiny bumps in the surface, while others have been completely uncovered or cut off completely from the pillars.
Although some EGGs will collapse down into new stars, others lack sufficient gas to create a new stellar candidate.
The EGGs are about a hundred times the Earth's distance to the sun, so the solar system would fit comfortably inside most of them. They last ten thousand to twenty thousand years.

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What is a Supernova Remnant ?

A supernova remnant is simply what is left over (i.e. the remnant) of a supernova. That probably isn't a very helpful definition, so I'll try to explain what I mean. First, I should probably define what is meant by the term "supernova." A supernova is simply the explosion of a star.

 The energy released in a typical supernova is on the order of 10⁴⁴ joules. (A joule is simply a unit of energy that physicists use). 10⁴⁴ is a 1 followed by 44 zeroes! There is no comparison for this amount of energy that is even meaningful. Supernovae are so powerful that they can be seen from halfway across the universe (billions of light years!). Here we can draw a comparison. The farthest star you can see with your eye on a dark night is only a few thousand light-years away.

What causes a supernova ?

Stars live out their lives by burning (via nuclear fusion reactions) light elements like hydrogen into heavier elements like helium in their core. For a star like the sun, this process will go on for about 10 billion years
before it runs out of fuel. More massive stars have more fuel to burn, but they go through it much more rapidly, so they actually live shorter lives. When a star runs out of hydrogen, it will try to burn helium into even heavier elements, like carbon, nitrogen, and oxygen. If those elements sound familiar, they should. You're a carbon-based lifeform, and you're breathing nitrogen and oxygen as we speak. All of those materials came from the core of some ancient star that exploded and spread its materials around the galaxy, before the Sun and the Earth were even formed!

What happens after a star goes supernova?

An explosion of that magnitude doesn't simply dissipate in a short amount of time (at least not by human standards). A supernova remnant is simply the expanding blast wave from the explosion plowing through outer space, as well as the remains of what was once the star following behind it.

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What is a Nebula ?

A cloud of gas and dust in outer space, visible in the night sky either as an indistinct bright patch or as a dark silhouette against... (in general use) Any indistinct bright area in the night sky, e.g., a distant galaxy.

 A nebula is an interstellar cloud of hydrogen, helium, plasma and dust. They are often called "stellar nurseries" because stars are "born" within them.

There are many types of Nebula, some stars have nebula's around them when they approach the final stages of their lives as in Wolf Rayet stars.

Diffuse nebula which are nebula which have no defining shape or boundary.

 

Dark nebula are so dense that it obscures the light from the background(Such as the Horsehead Nebula), or that it blocks out background stars(Such as the Coalsack Nebula).

Reflection nebula are clouds of dust which are simply reflecting the light of a nearby star or stars. Such as the Witch Head Nebula.

Emission nebula is a cloud of ionized gas (plasma) emitting light of various colors. Such as the Eagle nebula.

Planetary nebula which forms from the shells of stars when they transform into white dwarfs. Such as the Cats Eye Nebula

Protoplanetary nebula which is formed from the rapid creation of a star via stellar evolution. Such as the Egg Nebula

Supernova remnants, the remains of a massive star when it explodes in a supernova explosion The resulting expanding shell of gas creates a diffuse nebula. Such as the Crab Nebula.

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How to become an Astronomer ? (A Guide for Students of All Ages)

Introduction - 

Astronomy is a very exciting and challenging subject which involves many of the other sciences such as physics, mathematics, chemistry and geology, and, more recently, even paleontology and biology.
Many people are fascinated by the splendour and enormity of objects in space and become amateur astronomers while still at school. Astronomy can be an engrossing hobby for people of all ages, and there are many clubs and societies in Australia which provide information and facilities for looking through quite large telescopes that would be out of the range of most lone amateurs. Because of the wide public interest in astronomy, many universities and colleges organise evening courses on the subject, designed for people who do not have an advanced scientific background. Some offer online courses in astronomy. There is a very well produced local magazine, Australian Sky & Telescope, which has lots of useful information for the keen amateur.

Professional Astronomy as a Career -

 Some people decide at some stage in their lives that they would like to earn their living by working on a particular aspect of astronomical research. They may not have had an amateur interest in astronomy from an early age, but have turned to this science through an interest in some astronomical application of mathematics, physics or another subject. Present day astronomers have a wide variety of backgrounds but with a common thread linking them all together. They have demonstrated the ability to master a particular facet of astronomical research, and they have a curiosity about nature that can drive them to spend long hours in an endeavour to reveal something new about the Universe. Note though that the employment situation in professional astronomy is very competitive, even for students who graduate with excellent PhDs.

How to Start -

A professional astronomer is a scientist. The path to becoming a scientist starts with the subject choices made during high-school. Here, the study of the sciences, especially Physics, as well as Mathematics is recommended. However, as for many other careers, a large part of a research scientist's job is also dependent upon the ability to write (a thesis, research papers, telescope proposals, grant applications,...) so English should not be undervalued. After high-school, the vast majority of those who go on to become professional astronomers will go on to university to continue their studies in physics, mathematics, engineering or computing. As part of university studies, students often undertake research projects in astronomy, although maintaining a breadth of studies beyond astronomy can only improve future prospects.
Being a professional astronomer is an intellectually challenging career, and after the completion of an undergraduate degree, those seeking to become professional astronomers continue into postgraduate research degrees, usually a PhD. This path can be either via a Research Masters degree or by achieving a first class Honours degree with a significant research component to demonstrate the ability to undertake research.
This marks the transition from being simply a learner of skills and knowledge to becoming an active researcher.
The move into postgraduate research also provides another opportunity, the chance to travel. Many Australian students make their choice for undergraduate study based upon their personal circumstances, such as the chance to remain living at home. For postgraduate studies, you may have to change university, either because your current university does not offer a research project in the area you are interested in, or you may want to join a large, internationally recognised group. Making such a choice requires you to do your homework and seek out where you want to go; in making such a decision, you should have decided what area of astronomy you wish to follow. There are a number of Summer School Scholarships and projects offered by the major institutions - these provide an excellent opportunity to mix with students already involved in the field as well as researchers and get an idea what is really involved.

What skills do professional astronomers need?

Many astronomers possess skills that are particular to their field. However, there are a number of generic skills that astronomers need to call on (starting with astronomy projects as undergraduates). These include:

Computer skills: All astronomers need to use computers, for tasks ranging from email and web access to extremely complex computations. These may be numerical simulations of the growth of the universe to handling of very large data sets or the design of the next generation of instruments. One issue that often comes as a shock to new students is that astronomers generally do not use WINDOWS-based systems, but rely on UNIX-like systems. Skill in this area can smooth the beginning stages of postgraduate study, and so experience gained as an undergraduate can be very useful. 

Scientific Writing: All scientists must write; papers, reports and even lecture notes, and the skill of scientific
writing is extremely important, and a lot harder to learn than many envision. It is a skill that can be gained through practice, and so reading and writing scientific reports as an undergraduate will give important experience that can be taken into a postgraduate degree and developed further.




Public Speaking: As with scientific writing, all scientists must be able to orally present their results to their peers. While some have a flair for public speaking, to others this skill must be learnt through continual experience. For many, the first experience of scientific public speaking comes during their undergraduate years with the public speaker is also a valuable skill. Local astronomy clubs welcome astronomers to speak at their meetings, while universities have outreach opportunities that also offer valuable experience.
presentation of research projects. Again, these can provide important experience that can be taken into postgraduate studies, but it can take quite a while to hone teaching skills and become an effective scientific speaker. Being an effective

Where to Go

Most universities can give you a good grounding in science, but it does help to attend a university that has an

astronomy department or that can provide some astronomy courses taught by astronomers, usually as part of an undergraduate BSc teaching programme. This becomes more important in the honours year of a degree course, or a masters degree, when staff in an astronomy or mathematics department can supervise a research project that can count for a large fraction of the marks for the course. Another advantage is that your ability and interests will be known to the astronomers at your university, who will support you when you apply to commence the next stage of your career as a postgraduate student undertaking an MSc or PhD degree.

The Daily Life of a Professional Astronomer

Professional astronomers are research scientists who strive to understand the properties and behaviour of objects in the Universe beyond (and including) our little planet. Astronomers may

• be involved in taking astronomical observations, using optical, infrared, millimetre or radio ground-based telescopes, or a range of satellite-based telescopes and detectors,
• work on developing astronomical theories, which make predictions which can in turn be tested by observation or computational analysis,
• interpret observations or theories using their knowledge of astronomy and other sciences and use computers to test their ideas mathematically.

The instruments used to analyse radiation from objects in the sky are often at the cutting edge of technology, and astronomers are also heavy users of the latest in computer technology, including the use of supercomputer techniques and robotic telescopes.
Contrary to popular belief, most astronomers do not spend most of their time at telescopes. An astronomer will often record enough data in a week's observations at a telescope to be kept busy back at their home institution for much of the year. Most of the work is done using computer analysis, so computer skills are very important, and astronomy graduates gain a wide range of computer skills.

Where to Find Employment

Here we must be careful not give a false idea of the number of positions available in astronomical research. After finishing your initial training and obtaining your research (PhD) degree, it is a important to gain some experience working as a research fellow at one or more local or overseas universities or observatories. Indeed, most astronomers find it necessary to take a succession of fellowships, each lasting two or three years and often in different countries. There is great demand for these positions and you will need to have a very good academic record to be offered one. There is a similar, if not even greater, demand for almost any kind of position in astronomical research within Australia. If you are able to join the staff of a university, then you will be likely to spend a significant proportion of your time teaching undergraduate and/or postgraduate students.
The typical astronomy postgraduate student becomes very expert in many aspects of computing, mathematical analysis, data reduction and instrumentation. These skills make astronomy MSc and PhD graduates very employable in many fields other than astronomy, with many find employment in areas such as high-performance computing and the finance industry.
As an example of where astronomy can lead a young person, look at the brief description of the career so far of

• Joss Bland-Hawthorn, Federation Fellow at the University of Sydney
  (see http://asa.astronomy.org.au/profiles/joss.html).
• Michael Burton, Associate Professor at the University of New South Wales
  (see http://science.uniserve.edu.au/faces/michael/michael.html).
• Marc Elmouttie, Teacher
  (see http://asa.astronomy.org.au/profiles/elmouttie.html).
• Tanya Hill, Astronomer at Melbourne Planetarium
  (see http://asa.astronomy.org.au/profiles/hill.html).
• Bryan Gaensler, Laureate Fellow at the University of Sydney
  (see http://www.physics.usyd.edu.au/profiles/profiles_gaensler.html).

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How to Tell the Difference Between Planets and Stars ?

Astronomy can be confusing! There's so much jargon involved, and it can be very difficult to tell things apart, both visually and verbally. However, there are telltale signs that seperate stars from planets. Here's how to do it with observations.

Steps - 

1. Get a good set of star charts. These always come in handy. Google Sky Map is functional and simple for the novice. Astronomy books, such as David Levy'sA Guide to Skywatching, go more in depth with diagrams, showing individual constellation boundaries and best viewing times. If you are looking for Uranus or Neptune, you'll need even more accurate star charts, such as Uranometria 2000.0.
   
   
2. Planets lie within a band known as the ecliptic, which contains the 13 constellations of the zodiac. It wraps around the sky, starting at the constellation Pisces, continuing through Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius, Ophiuchus, Sagittarius, Capricornus, and Aquarius. (These are also the names of astrological houses.) Remember that there are some bright stars on or near the ecliptic that may be mistaken for planets. These include Aldebaran (in Taurus), Pollux, Castor (in Gemini), Regulus (in Leo), Spica (in Virgo), and Antares (in Scorpius). These can also help you find planets on your own.
   
   
3. Planets don't twinkle. They are disks, like the sun and moon, and shine steadily. However, this is only apparent when weather conditions are not very good.
   
   
4.  All of the planets (except for Uranus, Neptune, and sometimes Saturn) are brighter than the brightest star in the night sky (Sirius). If it outshines every other star in the sky, it may be a planet.
   
   
5.  Note its color. Planets normally have more intense colors than stars. Mercury is grayish-orange, Venus is yellow, Mars is blood-red, Jupiter is silver, Saturn is yellow, and Uranus and Neptune are blue. Note that Aldebaran and Antares are also reddish.
   
   
6.  Planets move across the night sky with relation to other stars. If you find a suspected planet, check its position every day, and see if it moves around. Mercury and Venus will move against the background of stars for half their orbits.
   
   
7.  Through a large telescope, some planets will show detail, such as cloud bands or moons. Any detail will confirm it to be a planet. No matter how much you magnify a star, it won't show any detail. Jupiter, Saturn, Uranus, and Neptune have moons, which appear like small dots that accompany the planet. They also move around, but on shorter distances and timescales.
   
   
8.  If you can defocus the light from a star, it will make a pattern called an Airy disk, which is a set of concentric rings. Defocusing the light from a planet will cause it to turn into a simple blur.

Tips - 

• If you find a fuzzball that you cannot focus, nothing's wrong with you or your telescope. You've probably found a nebula or galaxy. If you see a bunch of stars in a ball, you've found a star cluster.
  
  
• If you find an object that moves around on the order of days but does not present a disk, it may be one of the brighter asteroids.
  
  
• If it moves around on the order of seconds, it's probably a satellite.
  
  
• If it has a tail, it's probably a comet. But comets brighter than most of the stars are extremely rare.
  
  
• If you have a telescope, you can track its position against the stars and sketch its movement every day. You can do the the same for its moons relative to the planet.

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How to Choose the Right Telescope ?

Ever been interested in space and the night sky? Well, these steps will start you off on a great adventure.

Steps -

 

1. The diameter of the objective lens or mirror is the most important number describing a telescope. Larger diameter lenses or mirrors allow higher resolution (ability to separate closely spaced objects) and will gather more light from faint astronomical objects. They also cost more. A good size for a first telescope is roughly four inches (100mm). Bigger tends to be considerably more expensive and more inconvenient. Bigger works better, of course, though not shockingly so.

    

    
   
   
   2. Magnification is relatively unimportant and is often hyped in advertising claims for inexpensive telescopes. In astronomy, the purpose of a telescope is mostly to collect light from faint objects, not to magnify them. Most visual observing is done between 50 and 200 power.

    

   
   
   
   3. Too much magnification just gives you a useless blur. A good rule of thumb to determine the maximum usable magnification is to multiply the diameter of the objective in millimeters by 2.5 (which means that the typical department store 60mm scope is only usable to 150x). In actual practice, on nights of extremely unusual atmospheric stability, you -may- be able to use a somewhat higher power, but don't count on it.
   

    

   

   
   

   4. The better eyepieces have larger "eye relief," which represents how close you have to get your eye to the eyepiece to observer clearly. If the eye relief is too small you will have to bring your eye very close to the eyepiece, and it will be all but impossible to observe for more than a few seconds at a time.
   

   
   

   

   
   

    5. Look for a steady mounting, an unstable or shaky mounting will ruin your observing experience. In general, the more massive the mount looks, the better it performs. When in doubt, spend more on a mount.
   

   
   

   

   
   

   6. Join an astronomy club and learn to use someone else's telescope before buying your own.
   

   
   

   

   
   

   7. Start with a pair of binoculars and learn to find things in the sky before buying a telescope. (Or, if you just want to see pretty objects, get a GoTo mount.)
   

   
   

   

   
   

   8. Don't expect a small telescope to show the same images that you see in astronomy textbooks, which are usually long time exposures and may have been taken by much larger professional grade telescopes. No telescope practical for most individuals to own will show significant color in nebulae to the naked eye, although bigger ones will show shape well, and many can reveal color through time-exposure photographs.
   

   
   

   

   
   

   
   

   
   
   

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How to Calculate a Light Year ?

A light-year is measured by the distance ( NOT time! ) light will travel in one year. This can be calculated by multiplying seconds in a year × the speed of light.

Steps -

Calculate Seconds in a year

 

1. The formula for working out seconds in a year.
   • Seconds in a minute × minutes in a hour × hours in a day × days in a year.
2. Multiply 60 seconds by 60 minutes.
   • 60 × 60 = 3,600 seconds.
3. Multiply 3,600 seconds by 24 hours.
   • 3,600 × 24 = 86,400 seconds.
4. Multiply 86,400 seconds by 365 days.
   • 86,400 × 365 = 31,536,000 seconds in a year.

Speed of Light

 

1. • 186,000 miles per second.
   • Roughly 300,000 kilometres per second.

Multiply by Speed of Light

 

1. • 31,536,000 × 186,000 = 5,865,696,000,000 miles per year. ( 5.865696 × 10¹² )
   • 31,536,000 × 300,000 = 9,460,800,000,000 kilometres per year. ( 9.4608 × 10¹² )

One light-year in words

 

1. Five Trillion, Eight Hundred Sixty-Five Billion, Six Hundred Ninety-Six Million miles.
2. Nine Trillion, Four Hundred Sixty Billion, Eight Hundred Million kilometres.

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The International Space Station: Inside and Out

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How to make an Astronomical Telescope at home ?

To make a simple telescope at home, you will need the following:

 

1. two magnifying glasses - perhaps 1 - 1.5 inches (2.5-3 cm) diameter (it works best if one is larger than the other)
2. a cardboard tube - paper towel roll or gift-wrapping paper roll (it helps if it is long)
3. duct tape
4. scissors
5. a ruler, yard stick, or tape measure
6. sheet of printed paper - newspaper or magazine will do

To assemble your telescope, do the following:

 

1. Get the two magnifying glasses and a sheet of printed paper.
2. Hold one magnifying glass (the bigger one) between you and the paper. The image of the print will look blurry.
3. Place the second magnifying glass between your eye and the first magnifying glass.
4. Move the second glass forward or backward until the print comes into sharp focus. You will notice that the print appears larger and upside down.
5. Have a friend measure the distance between the two magnifying glasses and write the distance down.
6. Cut a slot in the cardboard tube near the front opening about an inch (2.5 cm) away. Do not cut all the way through the tube. The slot should be able to hold the large magnifying glass.
7. Cut a second slot in the tube the same distance from the first slot as your friend wrote down. This is where the second magnifying glass will go.
8. Place the two magnifying glasses in their slots (big one at front, little one at back) and tape them in with the duct tape
9. Leave about 0.5 - 1 inch (1 - 2 cm) of tube behind the small magnifying glass and cut off any excess tube remaining.
10. Check to see that it works by looking at the printed page. You may have to play slightly to get the exact distances between the two glasses right so that the image comes to a focus.

You should be able to see the moon and some star clusters as well as terrestrial objects (i.e. birds).

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Astronomy - A Self Teaching Guide - Dinah L.Moche

Astronomy is a user-friendly guide for beginners. Chapters make it easy for you to quickly learn the main topics of a college level course. Sections clarify basic principles and contemporary advances. The Index enables you to look up concepts, definitions, facts and famous astronomers, fast. You can use the book alone or with a conventional textbook, Internet based or distance-learning course, computer software, telescope manual, or as a handy reference.

A list of objectives for each chapter tells you instantly what information is contained there. The first time a new term is introduced, it appears in bold type and is defined. Topics in each chapter are presented in short, numbered sections. Each section contains new information and usually asks you to answer a question or asks you to suggest an explanation, analyze, or summarize as you go along. You will always see the answer to the question right after you have answered it. If your answer agrees with the book’s, you understand the material and are ready to proceed to the next section. If it does not, you should review some previous sections to make sure you understand the material before you proceed.

A self-test at the end of each chapter lets you find out fast how well you understand the material in the chapter. You may test yourself right after completing a chapter, or you might take a break and then take the self-test as a review before beginning a new chapter. Compare your answers with the book’s. If your answers do not agree with the printed ones, review the appropriate sections (listed next to each answer).

On a clear night in a place where the sky is really dark, you can see about 2000 stars with your unaided eye. You can look trillions of kilometers into space and peer thousands of years back into the distant past. As you gaze at the stars you may wonder: What is the pattern or meaning of the starry heavens? What is my place in the vast cosmos? You are not alone in asking these questions. The beauty and mystery of space have always fascinated people.

Astronomy is the oldest science—and the newest. Exciting discoveries are being made today with the most sophisticated tools and techniques ever available. Yet dedicated amateurs can still make important contributions. This book will teach you the basic concepts of astronomy and space exploration. You will more fully enjoy observing the stars as your knowledge and understanding grow. You will be better able to surf the Web and to read more on topics that intrigue you, from ancient astronomy to the latest astrophysical theories and spaceflights. Now, begin reading about the enormous tracts of space and time we call the universe, and stretch your mind!

 Ebook Size : 10.1 MB

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Ideas and Opinions by Albert Einstein

A new edition of the most definitive collection of Albert Einstein's popular writings, gathered under the supervision of Einstein himself. The selections range from his earliest days as a theoretical physicist to his death in 1955; from such subjects as relativity, nuclear war or peace, and religion and science, to human rights, economics, and government.

IDEAS AND OPINIONS contains essays by eminent scientist Albert Einstein on subjects ranging from atomic energy, relativity, and religion to human rights, government, and economics. Previously published articles, speeches, and letters are gathered here to create a fascinating collection of meditations by one of the world's greatest minds. --This text refers to an out of print or unavailable edition of this title.

"Ideas and Opinions reveals Albert Einstein, perhaps the greatest scientist of all time, as a whole human being . . . a deeply moral and philosophical thinker, whose clarity in human affairs matched his clarity in science. . . .
Purity and inspiration shine through every page of this extraordinary book."

--Alan Lightman --This text refers to the Hardcover edition.

 Ebook Size : 13.4 MB

 

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Introduction to Astronomy and Cosmology - Ian Morison (eBook)

Astronomy is probably the oldest of all the sciences. It differs from virtually all other science disciplines in that it is not possible to carry out experimental tests in the laboratory. Instead, the astronomer can only observe what he sees in the Universe and see if his observations fit the theories that have been put forward. 

Astronomers do, however, have one great advantage: in the Universe, there exist extreme states of matter which would be impossible to create here on Earth. This allows astronomers to make tests of key theories, such as Albert Einstein’s General Theory of Relativity. In this fi rst chapter, we will see how two precise sets of obser-vations, made with very simple instruments in the sixteenth century, were able to lead to a significant understanding of our Solar System. In turn, these helped in the formulation of Newton’s Theory of Gravity and subsequently Einstein’s General Theory of Relativity – a theory of gravity which underpins the whole of modern cosmology. In order that these observations may be understood, some of the basics of observational astronomy are also discussed.

One of the first triumphs of observational astronomy was Galileo’s series of obsevations of Venus which showed that the Sun, not the Earth, was at the center of the Solar System so proving that the Copernican, rather than the Ptolemaic, model was correct In the Ptolemaic model of the Solar System (which is more subtle than is often acknowledged), the planets move around circular ‘epicycles’ whose centres move around the Earth in larger circles, called deferents.  This enables it to account for the ‘retrograde’ motion of planets like Mars and Jupiter when they appear to move backwards in the sky. It also models the motion of Mercury and Venus.

Galileo’s observations, made with the simplest possible astronomical instrument, were able to show which of the two competing models of the Solar System was correct. In just the same way, but using vastly more sophisticated instruments, astronomers have been able to choose between competing theories of the Universe.

Looking up at the heavens on a clear night, we can imagine that the stars are located on the inside of a sphere, called the celestial sphere, whose centre is the centre of the Earth. 

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Encyclopedia of Astronomy & Astrophysics (eBook)

Publisher: Taylor & Francis | ISBN: 0750304405 | edition 2001 | DJVU | 5306 pages | 143 MB

Encyclopedia of Astronomy and Astrophysics is truly a landmark publication. Not only is it the most comprehensive and up-to-date work of its kind but it is also the first astronomy encyclopedia to be released in both print and Web formats. From astrophysical theories to astronomical objects to historical events to current space exploration, this work covers the entire range of human investigation of the cosmos.
The print version consists of more than 3,000 entries, of which 630 are primary articles discussing important theoretical and observational results of astronomical research, including entries as varied as Climate, Galaxies, Jupiter, and Telescope engineering. The work is especially strong in its coverage of topics related to the sun and solar physics. All of these lengthy articles provide both an overview and state-of-the-art review of the subject matter. Each includes at least three illustrations and a bibliography of relevant print and Web resources.

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What causes gravity?

Though some scientists theorize that gravity is caused by particles called gravitons, most agree that gravity is a product of mass. Everything with mass, from a dust mote to a star, exerts a gravitational pull. The force of the pull, however, increases with mass and proximity to the object. So a small object can only attract another small object that's nearby, but a large object, like a planet or a star, can pull in objects from across a vast distance. Einstein revised this theory further, saying that when a large mass causes a distortion in space, objects that come within that distortion will be attracted to the mass.

Of course, gravity in the movies can be quite different from real-life gravity. Often, weightlessness is depicted in the movies as the absence of gravity; however, the absence of gravity does not actually cause weightlessness. The people inside a spacecraft are actually in a state of what's called "free fall," as is the craft itself. In movies, free fall usually is staged by using wires and pulleys to make the actors seem to float. For Apollo 13 in 1995, the crew actually filmed short bouts of free fall aboard NASA's KC-135 "Vomit Comet" aircraft [source: NASA].

In general, it's easier to film without having to deal with weightlessness, and in real life, too much time spent in micro-gravity conditions can be unhealthy. For both these reasons, sci-fi movies often invent ways to artificially increase or decrease gravity. Spacecraft in both Star Trek and Star Wars movies have gravity fields that can be turned on during flight, and space suits have thrusters to keep astronauts grounded. Some movies, such as 2001: A Space Odyssey and Mission to Mars, depict the use of centrifugal force, which is actually a known way to produce artificial gravityOthers depict future technologies not yet known to us.

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Astronomy: The Solar System and Beyond, 6 Edition (ebook)

Description -

Michael A. Seeds, Dana Backman, "Astronomy: The Solar System and Beyond, 6 Edition"
Br..ks.C.e | 2009 |512 pages | PDF | 61.8 MB

With this newly revised 6th edition of ASTRONOMY: THE SOLAR SYSTEM AND BEYOND, Mike Seeds and Dana Backman's goal is to help students use astronomy to understand science and use science to understand what we are. Fascinating and engaging, this text illustrates the scientific method and guides students to these fundamental questions: "What are we?" and "How do we know?" In discussing the interplay between evidence and hypothesis, The authors provide not just facts, but a conceptual framework for understanding the logic of science. The book vividly conveys their love of astronomy, and illustrates how students can comprehend their place in the universe by grasping a small set of physical laws. Crafting a story about astronomy, The authors show students how to ask questions to gradually puzzle out the beautiful secrets of the physical world. With the use of mathematics set off in boxes, the book's presentation is flexible and allows instructors to teach to differing student levels. This is the only Seeds/Backman text to be written using a traditional planets-first approach. The revision addresses new developments in astrophysics and cosmology, plus the latest discoveries, from Mars' buried water to proto-galaxies at the limits of the observable universe.

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Where Did The Moon Come From? (eBook)

The current standard theory of the origin of the Moon is that the Earth was hit by a giant impactor the size of Mars causing ejection of iron poor impactor mantle debris that coalesced to form the Moon. But where did this Mars-sized impactor come from? Isotopic evidence suggests that it came from 1AU radius in the solar nebula and computer simulations are consistent with it approaching Earth on a zero-energy parabolic trajectory. But how could such a large object form in the disk of planetesimals at 1AU without colliding with the Earth early-on before having a chance to grow large or before its or the Earth's iron core had formed? We propose that the giant impactor could have formed in a stable orbit among debris at the Earth's Lagrange point $L_4$ (or $L_5$). We show such a configuration is stable, even for a Mars-sized impactor. It could grow gradually by accretion at $L_4$ (or $L_5$), but eventually gravitational interactions with other growing planetesimals could kick it out into a chaotic creeping orbit which we show would likely cause it to hit the Earth on a zero-energy parabolic trajectory. This paper argues that this scenario is possible and should be further studied.

 Comments: 64 pages, 27 figures, accepted for publication in AJ
 Subjects: Astrophysics

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The Birth And Death Of The Sun (eBook)

How did our sun come into being? What keeps it hot and luminous, and what will be its ultimate fate? In this fascinating and informative book, George Gamow - renowned physicist and author of the best-seller One Two Three... Infinity - outlines the discoveries and theories that illuminate the evolution of our world. One of the founders of Big Bang theory, Gamow employs language that's both scientifically accurate and simple enough for nonspecialists to trace the development of atomic theory from its earliest articulation in 375 B.C. through studies of nuclear reactions and radioactive decay. Along the way, he discusses the formation of the stars and planets, the nature of red and white dwarfs, the dimensions of our stellar system, and the infinity of space. 1952 ed. 60 figures. 18 halftones.

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