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JOURNEY THROUGH THE SOLAR SYSTEM

 

Our ancestors identified some patterns in the sky, which we call constellations. There are altogether eighty-eight constellations in the sky, of which the one called Hydra is the largest. Can you see it? In olden days this was believed to represent a celestial water snake, the multiheaded monster overcome by Hercules as one of his twelve labours. The smallest constellation is Crux- the Southern Cross.
 

Let me introduce my wonderful imaginative machine. I call it the time machine. It has the capability to transport us safely deep into the past or the future in the twinkling of an eye. Further in it we can pass months or even years in seconds. You may think that I am crazy. But, please suspend your disbelief and join me.
 

Inside the time machine, lets see how our sky changes as our earth complete one revolution around the sun, which we call a year. Note those bright objects in the sky. We would be passing one year in few seconds to see the changes that occurs in the sky. Ohhhhhh! Did you observe that those objects are shifting their positions very peculiarly with respect to the background, which is also changing, but not in the same way as those bright objects? If you were a keen observer, you would notice that the stars at the background maintain their relative positions with respect to one another. So, those bright objects cannot be stars. They wander among the stars. They are the planets – the other planets of our solar system. Well from earth with the unaided eye you can observe five planets on our solar system. But the astronomers have found out that there are altogether nine planets in the solar system.
 

 Our ancestors were keen observers. They observed the yearlong change in position of the planets. They observed this year after year. Particular reference may be made to the Alexandrian school in Egypt, where Appolonous, Hipparchus and Ptolemy studied in different periods. In those days people gave a lot of importance to the Earth. They thought that Earth was the center of the universe, the geocentric concept. They suggested that the forward and backward motion of the planets is due to the fact that planets move in epicycles, meaning that planets move in circles and simultaneously circle the Earth. At this juncture it would be worth mentioning that our ancient astronomer Aryabhatta also suggested the diurnal motion of earth, there by departing from the then popular static concept of the earth. But it was Copernicus who said that the earth and all other planets move around the sun. This is known as the heliocentric concept of the solar system.
 

Now let’s move with our time machine far away from earth, and observe how our solar system would look like. There you observe the planets moving around the sun. Further you observe so much dust and rocks, some as big as mountains mostly in-between those two planets- the red one we call Mars and the other one called Jupiter. These objects are called asteroids. What else is moving out there? Did you notice as it approaches the sun, a kind of tail develops and the direction of this is just opposite to the sun? These objects are called comets. They are actually chunks of ice and dust expelled from that region surrounding the sun much further than the last planet Pluto. That cloudy region is called Oort cloud, after its discoverer. The sun, the planets, asteroids, satellites of planets, comets, interplanetary dust; all these constitute what we generally mean by the solar system.

Observe our sun. It’s just like a golden disc. It’s shining in the darkness of space. This we generally never experience from the surface of Earth. As seen from Earth, whenever the sun rises the sky is full of light. The blue colour of the sky is infact due to the scattering of the blue portion of the sun’s visible spectrum by the dust particles in our Earth’s atmosphere. To study the sun in detail, astronomers from Earth have sent the Solar and heliosperic observatory, called SOHO. What do you feel about a trip to the sun with our time machine?

 

Infact it will never be physically possible to land on the sun. But our time machine will work wonders. Let’s start. Just as we go, lets use the onboard artificial eclipsing technique to eclipse the sun. Nature plays this game by moving the moon to block the visibility of sun’s disc from us on Earth for a maximum duration of seven and half minutes. But we can recreate this with our artificial techniques. As we do so, just go on observing, see, there…, the visible disc of the sun is completely blocked and we observe the visible halo of the sun. Astronomers call this halo the corona. Actually this is the outermost layer of the sun’s atmosphere. In this layer the charged particles move out from the sun at an enormous supersonic speed of five thousand kilometers per second. But from Earth the glare of the photosphere so dominates the sky that we miss (to see) the corona. Here we dock our time machine with SOHO. In a rare celestial spectacle two comets were seen plunging into the sun’s atmosphere in close succession on June 1 and 2 of the year 2001 by SOHO. The demise of the comets was followed the same day by a dramatic ejection of hot gas and magnetic energy known as coronal mass ejection. Remember we are in a place where one can never send instruments, let alone humans. Here the coronal temperature is million of degrees. Moving more closer we observe another layer, which is different from the corona. Here we observe fire arches and jets moving out. This layer is called chromo sphere. Ultimately we come to the layer, which is visible from the surface of the Earth. This layer is called photosphere.

Let’s move to Mercury - the first planet and the smallest in the solar system with the exception of Pluto. Mercury’s one-day equals nearly two months of Earth time, and one year is nearly three earth months. This planet is one of the hottest as well as the coldest in our solar system in the sense that, during rotation the part exposed to the sun is the hottest while the unexposed half is the coldest. But the distinction of the hottest region in the solar region goes to some one else, keep guessing!

Whatever photographs we have gathered about this planet were taken from the Mariner 10 spacecraft during the year 1974. Further, what a surprise! See, if your weight on Earth were one hundred kilograms, then you would weigh only forty-one kilograms on Mercury. Our astronomers are planning to send the space probe Bepi Colombo in 2009. The mission gets its name after the Italian mathematician Giuseppe “Bepi” Colombo.

Next let us proceed to Venus. Named for the Greek goddess of love and beauty, the second planet from the sun is often called Earth’s Sister. Although both of them have the same size, the differences between them outweigh the similarities. Venus can be spotted early in the morning or late evening depending on the season and is, therefore, called the morning or evening star.

 
 
 

Let’s take a close look at this planet.
 
 
 

What a strange world it is, a noxious atmosphere consisting chiefly of carbon dioxide and sulphuric acid. The temperature is so high that “lead” would melt. This is the hottest place next to the sun in our solar system. Further, look over there. Did you observe? The sun is rising in the west. This is because Venus rotates retrograde. This planet’s year is shorter than its day: lest this statement appears confusing, the time taken for one revolution round the sun is less than the time taken for Venus to rotate on its axis once. Its atmospheric pressure is nearly ninety times that of Earth’s. If we physically stand on this planet, we would be completely crushed.
 
 
 

It’s literally hell here. Humans can never never think of colonizing Venus. Further there are no natural satellites for this planet. Let us rush away in our time machine to Mars, the red planet.
 
 
 

This planet, red in colour due to the presence of rusty iron in the soil, is named after the roman god of war. It is very similar to our earth in many respects and, like the moon, the most targeted by humans to explore on foot. Here we observe from the time machine that the length of a year and that of a day is nearly same as ours on Earth. Further, it has mountains, valleys, riverbeds and polar ice caps. We also observe that it has seasons, a thin atmosphere consisting chiefly of carbon dioxide, nitrogen and argon. Then there are clouds, wind, dust storms, and a solid rocky surface. Due to its very thin atmosphere, the atmospheric pressure is also very low. Although we observe no water here, but there are lots of riverbeds visible, giving an impression that water might once have flowed on its surface. The Viking orbiter had photographed Tharsis Bulge, a cluster of shield volcanoes that reach heights of eighteen to twenty six kilometers, much higher than any mountain range on Earth.
 
 
 

The sky is pink in colour. This is the result of sunlight being scattered by fine dust particles suspended in Mar’s atmosphere. In 1877 Mars was discovered to have two small moons, the Phobos and Deimos, named after the god Mar’s chariot horses, “Fear” and “Panic”, respectively.

[DEIMOS]                [PHOBOS]

Have you ever watched a meteor shower?
 
 
 

The best way to watch a meteor shower on Earth is to sit back and relax under the night sky. Simply spread a blanket on the ground, spray your self with favorite insect repellant, layback and enjoy nature’s own fireworks display. But Meteor showers on Mars would be very different with explosions, shock waves, and violent lightning flashes. (Effects HUGE SOUND AND LIGHTNING)See that lightning. May be a meteor had crashed there!
 
 
 

Meteors are space debris that enters a planet’s atmosphere.
 
 

[MARS GLOBAL SURVEYOR]
 

In the middle of February 2001 The Planetary Society’s Red Rover Goes to Mars mission made planetary exploration unique. Students were the first members of the public to direct a camera aboard a spacecraft orbiting another world, the Mars Global Surveyor.

 

Scientists now speculate that about an area of one million square miles of Mars might be green, unfortunately not like grass or vegetation, but green as in olivine- a mineral of iron, magnesium and silica.
 
 
 

Any way we have to explore Mars in greater detail to refine our knowledge of this earth- like planet. But lets not stop. Lets aim towards Jupiter, the largest planet in our solar system. We may have strange encounters in the space between Mars and Jupiter. Lets GO!!
 
 
 

Hey!! Observe those rocks ranging from pebble size to as large as mountains floating in space. This region is a potential danger point; a collision may destroy any space ship. Ooh! Don’t worry; we are in a time machine. This region is called Asteroid belt.
 
 
 

Some of the asteroids are categorized as Potentially hazardous, due to their closeness of approach to our planet Earth. On the morning of September 1, 2000 an asteroid at a distance about twelve times the moon’s distance further away from earth, named QW7 was discovered.
 
 
 

On February12, 2001 Shoemaker spacecraft made history. To know about it lets go back to that date with our time machine. It is around 3:04 EST. What a wonder! Shoemaker is touching down on the asteroid called Eros. Just watch …….it survived the touchdown. This is the first time a spacecraft has landed on an asteroid.
 
 
 

Now we are near Jupiter.With the help of our time machine we can spend a Jupiter year very fast. Here the year is pretty long, equals nearly twelve earth Years. But the days are very short; little less than half the earth day. Further the mass of Jupiter is nearly three hundred and seventeen times that of earth and you can accommodate around 1300 Earth’s inside Jupiter.

  
SATURN

This giant planet is more massive than all the other planets in the solar system combined, plus the atellites, the asteroids and all the Comets! Its largest satellite, Ganymede is larger than the Planet Mercury. Each of the “Gallelian Moons”, discovered by Galileo in 1610, are larger than the planet Pluto. In total our astronomers have discovered twenty satellites of planet Jupiter.
 
 
 
 

Jupiter is a gas giant consisting chiefly of Hydrogen and Helium. The atmospheric pressure is so high that there is no clear boundary between its liquid and gaseous phase. Look there, did you see that vast red area in the atmospheric surface of Jupiter, yes that one. That is called the great red spot of Jupiter. The diameter of the red spot is so big that it can easily engulf two Earths. It has been known since the 1970’s that Jupiter has rings rotating in the same direction as their parent planet. But, recently a new ring rotating opposite to the rotation of Jupiter and its moons has been discovered.
 

[ JOVIAN MOONS]

Spacecraft Galileo was launched in 1989 primarily to study Jupiter. It entered into orbit around Jupiter on December 7, 1995. The Discoveries made by spacecraft Galelio were spectacular. To name one: the discovery of an atmosphere of Hydrogen and carbon dioxide on one of the Jupiter’s satellites.
 
 
 
 

Are you interested in climbing tall mountains? Well why not try at Io, the closest moon of Jupiter. This moon of Jupiter has some of the tallest mountains in the solar system. Just for comparison the tallest mountain in Io is 16.8 kilometers high whereas Mount Everest is only 8.8 kilometer in height. These mountains appear to be non volcanic in nature, unlike Olympus Mons, a volcanic mountain in Mars having a height of 27 kilometers, the tallest in the solar system. Io in simple phrase can be described as a world of fire and ice.
 
 
 

Near Io we observe Ganymede, the largest moon in the solar system. It contains fifty percent ice, while the moon Callisto is the third largest moon in the Solar system next to Ganymede and Titan of Saturn, where we will be going next. The Galileo spacecraft had discovered an atmosphere of hydrogen and carbon dioxide on the moon Callisto.
 
 

[SATURN]

Now lets move out of Jupiter and command our time machine to take us to Saturn. Here we arrive. As we spend a Saturnian year with Saturn, we observe that the duration of the year is pretty long, nearly twenty-nine and half Earth years. The Saturnian day is very small, less than half an earth day. In a giant beam balance if we measure the mass of Saturn, we would require ninety-five Earths for balancing.

 
 
 
 

From the onboard instruments that are similar to the one sent to this planet

 

Saturn has altogether thirty satellites. Titan, the largest moon of Saturn is the only satellite having nitrogen rich Earth like atmosphere. Lets land on one of the satellites of Saturn and observe how Saturn rises above the satellite’s horizon.
 
 
 
 

Here we are nearing Uranus. The mass of Uranus is nearly fourteen and half times that of Earth.
 

    

Uranus has a bluish – green atmosphere. Lets descend on the planet. The axis of this planet is tipped almost exactly on its sides. This results in its poles spending 42 years in sunlight and 42 years in darkness during one Uranian year, which equals 84 earth years. Uranus is the third gas giant and it’s the seventh planet from the sun. For the first time from the images relayed by the Hubble space telescope, our astronomers saw six distinct clouds in the northern hemisphere of the planet. Further the total number of known satellites of this planet is twenty-one. Of these, eight of them revolve around the planet in less than 24 hours. The satellite Miranda, with its rolling hills and cratered lowlands, is geologically interesting to astronomers.
 
 
 

Lets leave Uranus and move towards Neptune. Amazing, the length of a Neptunian year is about one hundred and sixty four Earth years. But its days are very short, a little more than half an Earth day. Further this planet is also quite massive, almost seventeen times that of Earth.

In August 1989, Voyager 2 captured images of this planet. Its atmosphere mostly consists of hydrogen, helium and some hydrocarbons. And this creates the planet’s bluish colour. Voyager 2’s camera has revealed a continuous ring system. The total number of moons discovered till date is eight. The storm and winds in Neptune’s atmosphere are the fastest in the solar system, which show dramatic changes within few months, or even weeks. Further precise measurements shows that Neptune, like Jupiter, radiates about twice as much energy as it receives from the dim and distant sun. This may be attributed to some internal source of energy.
 
 
 

Neptune’s large, icy moon Triton has a variety of features that make it unique in the solar system. It is the coldest place in our solar system, with a temperature of -236°C. And what a surprise, this is the only moon in the solar system that orbits “backward” around its planet. Next leaving Neptune we procede towards Pluto.
 
 
 

If you are interested in visiting a place having the longest annual duration, the best place to do so is to be on Pluto. The length of a Plutonian year is two hundred fourty eight and a half Earth years. Let us imagine a Plutonian with a 60-year life span. He can live 15000 years with us in Earth. Mind boggling, isn’t it? The days are also very long, a little less than six and half earth days. Only one satellite of Pluto, called Charon has been discovered. It’s the ninth and the last planet of our solar system. As all of you can see, unlike the gas giants of the solar system, Pluto is a small, icy planet with a very thin atmosphere. Pluto may resemble Neptune’s moon Triton. Pluto’s surface is covered with methane ice, while Charon is covered with water ice. Pluto and Charon rotate almost synchronously. Further Charon is the largest satellite relative to its planet in the solar system.
 
 
 

Taking a bird’s eye view of this planet’s orbit, we observe that it is an eccentric and inclined orbit. For about 20 years out of its 248.5-year orbit, Pluto is actually closer to the sun than Neptune. This occurred recently during 1979 to 1999. During these twenty years Pluto experiences a relatively warm temperature.
 
 
 
 

Recently a comet named 2000 CR (105) is observed to have a highly elongated orbit taking 3175 years to go round the sun, having a closest distance to sun much beyond the orbit of Neptune. To explain the behavior of this comet scientists find it necessary to assume that there is a planet of Mars-size at an average distance of 15 billion kilometers that could scatter this comet in its present orbit. Is it the tenth planet of our solar system?
 
 
 
 

Astronomers have discovered other planetary systems too. This was possible by observing the wobble of certain stars, taking it as the evidence of the presence of an orbiting planet, which was later, confirmed by space telescopes. The discovery of over fifty extrasolar planets in recent years is another mystery. Scientists have discovered planets with mass similar to small stars, and further wandering planets not attached to any stars, thereby questioning the very definition of planets. Truly nature is mysterious and there in lies its beauty.
 
 
 

So friends let’s realize our address in this universe. Our planet Earth is one of the nine planets revolving an ordinary star called the Sun, which is one among the millions of stars round in our galaxy the Milky Way. The Milky Way is one among millions of galaxies forming our universe. Further our solar system at the edge of the Milky Way circles around the center of the Milky Way at a speed of 220 Kms. per sec.; and the entire galaxy flies at a speed of 600 kms. per sec in space.
 
 
 

Lets return to our home planet Earth. Above Earth’s atmosphere, have a look at the marvelous International Space Station under construction. Danis Tito is the first common man to visit it. See how he is floating in zero gravity.
 
 
 

With the help of our wonderful machine we have traversed the solar system in such a small duration of time. As time passes a new day on Earth begins. The sun rises in the east. Mother nature presents the infinite variety of our wonderful planet, a kaleidoscope of towering mountains, thundering waters, dense forests, unpleasant volcanic eruptions, icy polar regions, killer earthquakes, evergreen country sides and much more. Let us feel proud to live in this planet and try to understand more and more about the universe, which is still a mystery for all of us. I bid farewell to all of you and hope to see you again.