THE WONDERFUL CALICUT SKY

 

Setting: A sky observation programme at Calicut Beach. An assembly of ten students of varying ages. The sky is clear with moon at the eastern sky nearing its first quarter. The jubilant group is awaiting for the planetarian to come and introduce them to the fantastic night sky, thereby unveiling the numerous mysteries associated with it as discovered by our astronomers, scientists and engineers.

 

Planetarian (pl): Good evening every body and welcome to the observation programme.

          

Visitors (chorus): Good evening sir.

                     

           v1: Is it evening throughout the Globe?

                    

           pl: No, for example now it’s afternoon at London. Let me elaborate. The earth rotates from west to east about its axis.

 

           The two points where the earth’s imaginary axis of rotation meets the surface of the earth are the north and the south poles .

 

           The circle , whose plane contains the centre of earth and is perpendicular to the earth’s axis is called the terestrial equator.

 

           The section of earth’s surface cut by a plane passing through the earth’s axis of rotation is called a terrestrial meridian.

 

           Thus every place has a meridian.

 

           The meridian of Greenwich in England is taken to be the prime meridian.

 

The latitude of a place is its distance north or south of the equator, measured in degrees between equator and meridian of the place.

 

           The longitude of a place is the distance east or west of the equator between the prime meridian and the meridian of the place.

 

Again, since the earth rotates from west to east, at a place, which is to the east; the sun or, a fixed star, crosses the meridian earlier than a place, which is to the west.

           The sun describes a complete circle in the sky in course of 24 hours and the same is with all other fixed stars.

 

So, for places separated by one degree, the time difference would be 4 minutes. Here we have to remember that 360 degrees equals 24 hours or 1440 minutes, as 1 hour equals 60 minutes.

 

The Greenwich time is taken as the international standard. For any place to the east of Greenwich, we are to add 4 minutes per degree.

 

           Similarly for any place to the west of Greenwich, we are to subtract 4 minutes per degree.

 

           The longitude of Calicut is 79.5 degrees. Hence, we have to add 5 hours 18 minutes to Greenwich mean time.

 

           In our country, the centre along the breadth has been adopted as the central station.

 

           Accordingly, we get local mean time of this central station, which is known as the Indian Standard Time or IST.

 

India’s western most tip in Gujarat is located at 68 degrees east longitude and its North eastern edge in Aranuchal Pradesh lies at about 97 degrees east longitude.

 

Hence, the people of Gujarat will witness sunrise one and half hour after the people in Aranuchal pradesh see it. Isn’t it wonderful?

 

          

           I have learnt from books that they are formed by the exhaust from Jet plane.

 

           But I fail to understand, how these smoke stay intact in the path for such long time?

 

pl: Actually the condensation trail, or contrail left behind as a jet streaks across the sky is just another form of cloud, due to extreme cold condition at these height which is 10 to 13 kilometers.

 

           v3: I had seen illuminated circles around sun. But many times I have seen such circles around Moon. What are they?

 

pl: These circles, also called HALOS, are formed when light strikes certain ice crystals in the atmosphere.

 

           v4: The sky is so beautifully touching the Arabian sea. This is our horizon. Isn’t it sir?

 

pl: Exactly, but it is an illusion. Our Earth is spheroid in shape. So, due to perception, the sky appears to touch the ground in form of a circle.

 

v5: Sir, what is that bright object in the sky?

 

           pl: It is the planet Jupiter.

 

           v6: How are you so sure about it?

 

pl: Well, your query can be split into two parts. First, how do I know that its a planet and not a star. Secondly, how do I identify it as the planet Jupiter?

 

            v6: Exactly sir, that’s what I meant.

                   

           pl: So, regarding the first part ; if you observe this bright object regularly for a couple of months, you would see that its           position changes with respect to the surrounding dots of light. Further, the dots of light twinkle whereas this bright object does not. These properties make us identify this object as a planet. The surrounding relatively fixed twinkling dots of light are called stars.

                     

           v2: But sir, how did you certainly tell us that it’s the planet Jupiter?

                     

 

pl: Well, there are two ways. First, you may point a telescope or binocular to this object and conclude it to be Jupiter. Secondly, you may refer to a star chart.

                   

             v3: Star chart! What’s that?

                 

pl: It’s a specially designed chart in pictorial form which indicates the position of various stars. The brighter a star, the bigger it would appear on the chart. You should hold this chart over-head and turn it in such a way that the North, South, East and West marked on the star chart point to the correct directions. Now you can identify correspondingly.

 

v4: Ok, then how do we know, where the correct directions are ?

 

           pl: The Earth spins about its axis.

 

So, all the celestial objects rise in the east and set in the west. If we stand in such a way that our right hand is towards the East and left hand towards West, then our face will be towards North and our back towards South.

                   

           v5: How will Jupiter look like through a telescope?

                   

pl: Let’s see with our telescope. Can you observe the central disc of light with features on its surface? It’s the planet Jupiter. It is the largest planet in our solar system. 1300 Earths can be accommodated inside it.

 

            Also see the dots surrounding the central image. They are the satellites of Jupiter.

 

In 1610, Galelio was the first person to observe Jupiter with a telescope. He could locate four satellites with his telescope. These are called Galilean moons .Our astronomers have discovered thirty-nine satellites of Jupiter so far.

 

                                          

v6: Sir, how did Galelio conclude that these specks of light surrounding Jupiter are the satellites of Jupiter and not neighboring stars?

 

           pl: Yes, you have asked an intelligent question. Actually, if you observe Jupiter daily, you will find that these specks of light s           urrounding Jupiter change their positions around it in few days.

 

           So, Galelio interpreted these as satellites. Also, the observation of the satellites of Jupiter has other credentials to its credit.

 

           . The proof of Newton’s theory of Gravitation and the finite velocity of light were first confirmed by such observations

 

v1 : Sir, now the sky is totally dark with stars shining. But how do we remember the night sky? 

 

pl: Well, our ancestors were keen observers. They identified some patterns in the sky resembling some terrestrial or imaginary objects. Theses are called constellations. Here, you should understand that there is no intimate relation between stars of a particular constellation. They are very far apart from one another. As seen from earth, they appear to be grouped together.

                           

           v2: So, how do we remember the constellations?

                           

           pl: For that you must make some reference points. Just now, the most prominent constellation in sky is that one.

 

            Can you all locate that trapezium, which is intercepted at the middle by a line joining those three bright stars?

 

           That is the constellation of Orion. This is seen in sky during the months of January, February and March annually.

 

Mythological it represents a hunter or a warrior with his shield and club raised against the snorting charge of neighboring Taurus, the Bull. Next, there,...... that’s Taurus.

                       

           v3: Which is the brightest star in the Orion constellation?

 

pl: Can you see that bright red star. That is called Betelguese.

          

           It lies 310 light years away from us. A light year is the distance traveled by light in one year. It approximately equals 95 followed by 11 zeros in kilometers.

 

Now under those three stars forming the belt of Orion, if we focus our telescope, we observe an object of faint nebulosity. Its actually called Orion Nebula.

 

           A nebula is a cloud of gas and dust; the birthplace of a star.

 

           Orion nebula is estimated to contain enough gas to make a cluster of thousands of stars.

 

Remember those three stars forming the belt of Orion. If you move along the line joining them, you reach that bright star there. It’s the brightest star in the sky. Its called Sirius, in the constellation of Canis Major.

 

v4: We know that planets of our solar system reflect light falling on them. Our sun and other stars produce light by energy released from nuclear reactions. But how do nebulae emit light?

 

pl: There are nebulae which glow brightly, while there are others which are dark.

 

           In bright nebulae, the gas and dust is lit up by the stars that lie within or very close to them.

 

Remember the Orion Nebulae. Its a bright nebulae. By contrast, dark nebulae are visible only because they blot out light from object behind them.

          

 

Look there. This is the smallest constellation in our sky. Its called Crux, the southern cross. Coalsac nebulae, a dark nebulae is located there. Orion constellation also contains a dark nebula - The Horsehead nebula

           Some dark nebulae are seen as silhouette against bright

nebulae.

 

                         

 v5: Some time back you said that Orion nebulae is estimated to have enough gas to form a cluster of thousands of stars. What is a cluster of stars?

                         

pl: Stars sometimes group together in clusters of which there are two main types: Open clusters and globular clusters. Among them, the open cluster is less densely packed and irregular in shape.

 

Remember Taurus. There, can you see that V-shaped cluster of stars. That’s called Hyades Cluster.

 

           Further see there. Try to count the number of stars visible there. How many can you find?

                           

           v6: Six

                           

           v1: Eight

                          

           pl: Ok. Now let’s focus our telescope in that region of sky. Just observe. Hundreds of stars are visible.

 

           Its the Pleiades cluster.

 

Globular cluster are dense, ball shaped aggregations that can contain hundreds of thousands of stars. These clusters are much far away from us than open clusters. So, with small telescopes its difficult to see a Globular cluster.

 

v2: In school, we were told that nearly hundred thousand million stars make a galaxy. Then sir, how are these clusters able to remain as separate units within a galaxy?

                      

           pl: Some stars of a galaxy are gravitationally bound as a unit and have a common motion around the centre of Galaxy.

 

chorus: What are stars?

          

           pl: As explained earlier stars are born in giant clouds and dust called Nebulas.

 

           Due to some perturbation by other celestial masses, the materials in a Nebula get shaken and break into smaller nebulae.

 

           The internal gravity causes an individual small nebula to collapse inwards.

 

When the pressure rises to a certain level, the core of the nebula gets heated up. Then gradually over a period of one-lakh years, the nebula gets transformed into stars.

 

           The baby star continues to form and its force of gravitational collapse continues heating up the star’s centre.

 

When the core temperature reaches millions of degrees, thermo nuclear reaction starts. The star starts radiating energy in all forms including visible light.

 

The star stops shrinking, and blows off the remains of the nebula into space.

               

           v3: See that streak of light. Again there....shooting stars. Isn’t it?

 

 

 

pl: Yes, shooting stars, also called Meteor, are the light phenomenon which results from the entry of particles from space into Earth’s atmosphere.

 

v4: Sir, in text books we see Newton’s law of Gravitation. But I have heard something called Einstein’s law of Gravitation. How do they differ?

                     

pl: Actually they are different explanations for the same phenomenon, which explains the cause for planets moving around the sun.

 

According to Sir Isaac Newton, between any two material bodies there exist a force of gravitation, i.e., an influence for example, between sun and planets.

          

          

           But Albert Einstein said that there is no independent existence of space and time. We should speak of space-time.

 

          

 

Further, presence of a mass of matter distorts space-time around it, and other surrounding material bodies moves in path, which makes their motion easy.

 

v6:  Our nearest galaxy is -- Andromeda Galaxy. Isn’t it?

                     

pl: Correct, Andromeda galaxy is our nearest regular galaxy. Light takes more than 2 million years to reach us from Andromeda.  Can all of you observe that W-shaped constellation?

                 

           Chorus: Yes.

                     

           pl: Its the constellation of Cassiopea. Near it is located the Andromeda Galaxy. Let’s focus our telescope there.

 

Can you all see? Its Andromeda galaxy. Further, if you bisect the W and draw a straight line towards north, you reach the star there. This star never rises or sets. It lies along the axis of rotation of earth. It’s our pole star, Polaris.

                    

                      Long ago, there lived a king in India. He had two queens having a son each.

 

           The younger son was dear to the king, having the fortune to sit on his lap.

 

The elder son, named Dhruva yearned for this privilege. But no one cared for him. He was hated by the king, and ultimately thrown out of the kingdom.

 

 

 

With deep sorrow in his heart, Dhruva preceded towards forest, to seek help from the lord, the almighty. He meditated and pleased the lord.

 

           The lord appeared.

 

           On enquiring about Dhruva’s sorrow, the lord learnt that Dhruva wanted to be loved by his father and be on his lap.

 

          

Then came the boon from the lord that Dhruva will not only be cared by his father but would be immortalised in the sky in the form of a star. The whole humanity would see him for generations on Earth.

 

Ancient Indians immortalised this tale by identifying the Pole star by Dhruva.

 

v1: Look there.... those seven stars. Is it Saptirishi?

 

            pl: Yes. Its called Saptharishi. With the help of this constellation you can locate some more constellations.

 

            Astronomers call this constellation as Ursa Major.

 

           Now, join those two stars by an imaginary line and extend it. You will reach that particular constellation. Its called Leo.

 

           v4: So many stars, some blue, some red, some white. What is the significance of colour of stars?

 

           pl: Good observation. For many centuries scientists were trying to crack this puzzle.

 

           It was the genius of Meghnad Saha, an Indian scientist who showed that the colour represents the temperature of the star.

 

          

                      A blue star is a very hot star, and Red is a cool star. In between falls a white, yellow, and orange star.

 

 

So, now you may understand that red is not the hottest. Blue colour of a heat source indicates hottest temperature and red as coolest.

 

v1: Lets see moon through the telescope.

                    

          

 

pl: Yes, observe the craters. These are not revealed without a telescope. There lies the importance of resolving power. Also note that, we can see only one face of the moon. The other is hidden from us. This is due to the synchronization of rotation and revolution of moon around earth.

 

v2: Sir so many stars are there in the sky. Some are bigger than our sun. But still why is our night sky dark? It should be actually flooded with light, even in the absence of sun. Isn’t it?

 

pl: Actually, the number of stars, their luminous lifetime and the present size of expanding universe are such that the total starlight is too feeble to illuminate the night sky.       

 

Further as light has finite velocity, so some of the starlight, which you are seeing, now has actually left the star millions of years ago.

 

So, if a star 1000 light years away, stops shining now, we would come to know regarding the same after 1000 years.

 

 

           Sunlight takes around eight and half minutes to reach us.

 

 

 

           Light can travel seven and a half times around Earth in one second.

 

 

Before concluding, let me tell all of you our position in the universe. We are staying at a place called Calicut, a small city in Kerala, one among the Indian states, also called “God’s own country”. India is in the southern part of Asia, which is one of the five continents in a small planet called the Earth.

 

Here, mother nature presents the infinite variety of our wonderful planet, a kaleidoscope of towering mountains, thundering water falls, dense forests, unpleasant volcanic eruptions, ice polar regions, killer earth quakes, evergreen country sides and much more.

 

The earth along with other 8 planets revolves round an ordinary star called the Sun.

 

 

 

The sun is one among the hundred million stars in our Galaxy, the Milky way. Astronomers have estimated that there are ten thousand million galaxies in the universe.

 

           Now it’s late. We have been observing for quite some time. What I have shown is a part of the night sky.

 

          

 

           As Earth revolves around Sun, different constellations are visible at night in different part of a year.

 

          

 

           What you all didn’t see now may rise above the horizon late night or early morning.

 

          

 

           Some of them are in the daytime sky when sunlight dominates and forbids us to see them. So, lets conclude.

 

           Goodbye to all of you.

 

 

Chorus: Thank you sir.

 

 

******************************************************