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Natural Hazards: Impacts of Catastrophic Collisions
“I have grown, looking at sky and stars.” Many people can say this, including me. We loved to watch stars in night. We enjoyed the Sunrise and Sunsets. And offcourse, millions of people loves NASA’s Astronomy Pic Of the Day and they like to add APOD as their wallpapers. There are many more beautiful phenomena in the universe, like Solar Eclipse, Eagle Nebula, Aurora etc. We feel safe, cheer and enjoy our life. However, it does not mean that a smaller strike of any tragedy cannot happen even as you are reading this blog. For a horrible example, who was knowing about the latest Tsunami in Japan, before the date it occured?
The theory of gravity is not enough developed that you can exactly state the motion of a planet or star or any other material in the space. Some bodies, like dwarf planets, sattelites, meteoroids, have random motions. The most fearful motion is of meteoroids, the rock like structures. Usually these are found in between Mars and Jupiter as a belt. But when a meteoroid leaves the belt, the gravitational attraction of the earth, nearest planet to mars, can pull that into it. When a meteoroid enters the atmosphere, friction causes it to heat up and glow. Then we call it a shooting star or a meteor. Small meteors burn up completely as they pass through the atmosphere. Larger ones end up on earth as meteoroid. Impact craters are formed when a large meteoroid or comet crashes into a planet. One such massive natural hazard happened in past, which destroyed all the Dinosaurs.
Its a Mystery! – Simulacrum in Eagle Nebula
One of the Strangest photos that have Ever Been taken of space is that of the Eagle Nebula. The photo itself is supposed to show the birth of a star from the gaseous clouds.
When the photo was shown on CNN, [See Image1] hundreds of calls came in from people reporting — they could see a face in the cloud. When the color of the photo was adjusted, a large human form seemed to appear within the cloud. [See Image2]
Image 1: Simulacrum in Eagle Nebula-
Image 2
So What did you see here?
This is what attracts us to mysteries. Mystreries are beautiful.
Scientists have not been ab
le to explain this beautiful phenomenon.
Related Articles
- Picture of the Day – The Eagle Has Risen (spacefellowship.com)
- A star wrapped in the beautiful colors of the nebula that birthed it [Space Porn] (io9.com)
- The Pelican Nebula: Facts and FAQs (brighthub.com)
Introduction to Universe: Part IV: Black Holes
Image by NASA's Marshall Space Flight Center via Flickr
Black Holes
What are they?
Strange things happen to a star at the end of its life, as it converts to a red giant, black dwarf, white dwarf, supernova etc. (To know more read Part I of this series.)
Consider a star, having its mass is more than 3 times of the mass of the Sun. At the end of its life, it will collapse and will become more and more compact. This collapse will continue until the star becomes so compact and dense that Nothing…Nothing, not even light , would be able to pass through or escape from its gravity. Hence the star will become dark and it cann’t be viewed directly.
Now we say that our Considered Star is A Black Hole.
Nature and More about Black Holes
As of now, our star is a black hole. Now it will emit strong gravitational waves due to its giant mass-density. These waves will be strongest near the black hole and weakest at last approach of the black hole. Thus the shape of black hole’s effect area, will look like Whirl. This is the same as washing machine whirl. . 
Read Part I of this series Here
Introduction to Universe: Part III: Our Sun & Its Structure
Image via Wikipedia
So are you ready to enter into the Sun?
We may divide the internals of the Sun into following major parts:
• Corona
• Chromosphere
• Photosphere
• Solar Envelope
• The Core
Corona
Corona is the outermost part of the sun & you may see it when Full Solar Eclipses occur. The temperature of corona is about 2.7million°C, which is hot enough to emit ultravoilet and X-rays. The corona extends millions of kilometers into space above the photosphere and is very hot- millions of degree celcius.
Chromosphere
In a solar eclipse, a red circle around the outside of the Sun can be seen sometime. This is the chromosphere. The chromosphere is made up of the gases that extend away from the photosphere.Chromosphere is of red color, caused by the abundance of hydrogen. It has a greater (than Photosphere) temperature of about 10000°C. The Chromosphere merges into Corona & Photosphere.
Photosphere
The photosphere is the zone from where the sunlight we see is emitted. The photosphere is a layer of low pressure gasses surrounding the envelope. It is 400 km thick, with a temperature of 4500°C to 6000°C.
The Core:
The innermost layer of the sun is the core with a density of 160g/cm³ (10 times that of lead). The core might be expected to be solid. However, the core’s temperature of 15 million°C keeps it in a gaseous state. In the core, fusion reactions produce energy in the form of γ rays and neutrinos.
From the photosphere of the sun to the chromosphere and to the Corona , the temperature increases, while the same procedure follows up from the photosphere to the core of the sun (I mean temperature increases). Thus you may say in other words that the Photosphere is the COOLEST PLACE in the sun.
Spots in Sun? — SunSpots
The sun has enormous organized magnetic fields that reach from pole to pole. Loops of the magnetic field oppose convection in the convective envelope and stop the flow of energy to the surface. This results in cool spots (i.e. SUNSPOTS) at the surface which produce less light than the warmer part.
Sunspots are dark spots on the photosphere, typically with the same diameter as the Earth.
Sunspots have cooler temperatures than the photosphere. So our thoughts again changes here, that photosphere is the coolest part on the Sun— Now it is the sunspots.
The center of a spot is called the umbra, looks dark gray if heavily filtered & is only 4200°C (as compared to the photosphere at 6000°C).
Penumbra is the portion around the umbra, which looks lighter gray (if filtered).
Sunspots come in cycles, increasing sharply (in numbers) & then decreasing sharply. The period of this solar cycle is about eleven years. The largest spot ever measured (APRIL 1974) covered 18130 million km² i.e., 0.7% of the Sun’s visible surface. The life periods of these spots also vary—from a few hours to many weeks.
Polar Auroras
It is an effect of sunlight.
Polar Auroras are two auroras, the Aurora Borealis or Nothern Lights and the Aurora Australis or Southern Lights. These are lights that sweep across the sky in waves or streamers or folds. They are very often multi-colored and provide one of the finest spectacles in nature. They occur in Arctic and the Antarctic regions respectively. But the Northern lights can be seen as far south as New Orleans in America and the Southern lights as far north as Australia.
Comments and Suggestions are invited from the readers. You may mail me to gaurav.phys@gmail.com
Introduction to Universe: PART I : Stars and their types
Image via Wikipedia
What is it?
There are many millions of stars in the sky. In the whole heavens, fewer than 6000 stars are bright enough to be visible and at any one time, less than 2500 stars are visible above the horizon.
Stars account for 98% of the matter in a galaxy. The rest of 2% consists of interstellar or galactic gas & dust in a very attenuated form. The normal density of interstellar gas throughout the galaxy is about one tenth of a hydrogen atome per cm³ volume. Stars tend to form groups.
What I shall discuss here?
There are many types of stars in the universe having different name & definitions. I’ll discuss a few of them!
Major kinds of Stars according to numbers
• Lone Stars :These are alone and going on their own. Lone stars are exception in the Universe.
These donot follow up the condition to be in galaxy. And this is the difference between it & Single stars.
•Single Stars These are found in galaxy & are single (for example Our Sun). These do not number more than 25% of Stellar (Star) Population.
•Binary Stars or Double Stars These exist as couples of stars (e.g., Antares in Scorpio is actually two stars) and they are some 33% of stellar population.
The rest are •Multiple Stars (e.g., Capella & Alpha Centuri comprize 3 stars each, while Castor consists of 6 stars).
Note that, stars which appear single to the naked eyes are sometimes double stars. There are two stars revolving around a common center of gravity. They are also found in orbital motion round each other, in periods varying from about one year to many thousands of years.
Vivid types of Stars according to their nature
Red Giants
When the hydrogen, the main element in a star, is depleted, its outer regions swell and redden. This is the first sign of age. Such stars are called Red Giants.
Our Star, the Sun, is expected to turn into a red giant in another 5 billion years. Red giants are dying stars that has expanded greatly from its original size and gives off red light. They have gigantic dimensions.
Black Dwarf
It is the blackened corpse of a star. Ultimately it disappears into the blackness of the space.
White Dwarf
It is a tiny, dense, hot star, representing a late stage in the life of a star. The matter in it is so incredibly dense that a single teaspoonful of it would weigh several tonnes.
Supergiants
These are huge stars, with all their hydrogen fuel used up in their core, but continue to expand hundred of times bigger than its original size before they finally die.
Novae & SuperNovae
These are kind of stars, whose brightness increases suddenly by 10 to 20 times are more and then fades gradually into normal brightness. The sudden increase in brightness is attributed to a partial or outright explosion. In Nova, it seems that only the outer shell explodes, whereas in SuperNova the entire star explodes.
Variable Stars
There are stars that show varying degrees of luminosity.
Quasars
These are variable stars and are powerful quasi stellar sources of radio radiations.
Pulsars
These are also variable stars which emit regular pulses of electro-magnetic waves of very short duration.
© Gaurav Happy Tiwari, 2011
