Life similar to that on Earth requires carbon, oxygen, nitrogen, phosphorus and sulphur. If any of these were not present, life, as we know wouldn’t have originated and evolved. Apart from this, the planet should be at a particular distance from its star such that conditions (like temperature) are conducive to sustain life, it should have sufficient amounts of oxygen, water etc…. These are the main conditions for life to flourish in a planet. Since the universe is extremely big, it is entirely possible that an infinite number of planets satisfy all these requirements, giving rise to infinite number of civilizations.
Another possibility is that, life on other planets might be entirely different from ours, that we are not able to recognize. For example, silicon might be a substitute for carbon, giving the lifeforms a crystalline morphology and enabling them to exist even at high temperatures or there could be lifeforms that can breathe in Nitrogen and use ammonia as a substitute for water. We never know…
So, we accept that there is a very high possibility that life exists elsewhere. Now, the next question arises. Why haven’t we found one or why haven’t they made contact? Like I said, we probably aren’t intelligent enough to detect an entirely different lifeform. Moreover, how have we tried to make contact? The SETI uses radio frequency signals. Any of these cases is possible:
· Probably, they detected these signals, but are too primitive to know how to respond.
· Probably, their means of communication is entirely different from ours and hence, they did not think these radio signals were sent to make contact.
· In a more likely case - they responded, but we are not intelligent enough to detect or comprehend these signals.
· Probably they are much more intelligent than us that they just don’t care to respond to primitive, unintelligent civilizations.
One of the most interesting aspects of space science is the possibility that life could exist elsewhere in the universe. The thought that we might not be alone in the universe excites us. It might actually be true. The universe is so big that there is a very good chance that there could be infinite civilizations just like us or much more intelligent than us.
I believe you would have watched or atleast heard about the
There have been a number of occasions when people have speculated to have seen alien beings or alien spaceships (Unfortunately, no direct evidence of any such life form has been found yet). So, we all strongly believe that they are out there somewhere, waiting to be contacted.
So are we alone..?? If not why haven’t we had contact…?? Only time can give us the answer…..
Any idea what will happen to the Sun in the future?? The Sun has been shining for about 4.5 billion years due to thermonuclear fusion of hydrogen to helium. But, we all know that the hydrogen supply cannot last forever. The sun will eventually run out of fuel. That triggers the dramatic chain of events and the sun will undergo a radical change.
Once the hydrogen supply gets exhausted, the nuclear fusion in its core would stop. The core starts contracting under its own gravity and more importantly the outer shell swells considerably, which decreases its surface temperature and the sun becomes a giant red ball of gas – A Red Giant Star. The sun will swell up to such an extent that it will swallow all the inner planets including the Earth (It is estimated that in its red giant phase, the Sun will expand out to a radius of approximately 1 AU [AU – Astronomical Unit = 150,000,000 km], which is 250 times its present size). So that’s going to be the end of the Earth…Doomsday…
Good News!!! Fortunately for us, none of this is going to happen in the near future. It is estimated that the hydrogen fuel in its core will last atleast for the next 5 billion years. By the time all these happen, Mankind or any form of life, for that matter, might not even exist on Earth.
Slowly, our star continues to collapse under its own gravity and shrinks further. The gravitational field will eventually become so great that nothing can escape its pull, even light. Around the black hole, a boundary in space-time is formed which is called the Event Horizon. We should be nowhere close to the event horizon because any object which falls inside this has no chance to escape from it. So it’s wise to move as far away from it as we can and observe the black hole from a peaceful area.
We cannot actually see a black hole with our naked eye or using a telescope. Because it absorbs all the light that falls on it, reflects nothing just like a perfect black body. But watch the stars around it closely. The stars close to this black hole start rotating this seemingly empty region in space. The main feature of a black hole is its interaction with other objects in its vicinity. Gas from the nearby stars, like in the case of a binary star system, feed the blackholes and make them grow stronger. Sometimes, these blackholes merge with other stars or objects, which are suspected to be main reason for the formation of Supermassive blackholes in the center of most galaxies. All the matter, that enters the event horizon is accelerated towards the exact center, called the Singularity, where the gravitational pull is so strong and matter is crushed to infinite density.
Guess we have spent enough time in the past studying the life of this star which is going to remain a blackhole for eternity. So let’s come back to the present and see if we can spot this blackhole….wink! Wink!
Stars having masses similar to that of the sun become a White Dwarf after losing their expanding outer shell. The outer shell expands so much that it escapes the star’s gravitational force. White Dwarfs are very small, dense, hot stars whose nuclear energy supplies have been used up. They spend several billion years in this phase and eventually cool and fade out. So nothing dramatic happens during the final stages of these stars….So boring!!!
Don’t worry….our star is a massive one…so lets see what happens to it. The fusion in its core continues till so much iron gets accumulated in the core, that it is not able to support its own mass. Now, the most spectacular thing happens. The core suddenly collapses causing the electrons to collide with the protons to form neutrons or neutrinos. This sudden collapse produces shockwaves and causes the entire star to explode. This is called the Supernova Explosion. Supernovae are so bright that they can be easily spotted with the naked eye even if they are not normally visible. They can last for several weeks or months and during this short period they radiate as much energy as the sun does during its entire lifetime. Supernova is an important source of heavier elements in the universe and plays a very significant role in the formation of new stars.
After the supernova explosion, the remnants either become a Neutron Star or a Black Hole. Neutron Stars are extremely dense stars (a mass 3 to 4 times that of the sun is accommodated within a diameter of a few kilometers). However, the remnant left by our star after the explosion is greater than 4 times that of the Sun…which means that our star is going to turn into one of the strangest and most mysterious objects in the universe….A BLACK HOLE!!!
During this phase, we can see a Star similar to the Sun producing heat and light due to the thermonuclear fusion reaction. It has been estimated that stars spend about 90% of their lifetime in this phase. During this phase, the proportion of helium in its core keeps increasing and loses a very small fraction of its mass. The only visible differences will be a considerable increase in its temperature and luminosity. The Sun’s luminosity is estimated to have increased by about 40% since it reached the main sequence. (The initial mass and the proportion of heavier elements influence the evolution of a star). Nothing spectacular happens during this phase. Massive stars burn out their fuel faster while the lighter ones burn their fuel slowly and can last from tens to hundreds of billions of years.
So let’s keep moving forward in time, till we begin to see signs of expansion at the outer layers of the star. The star is beginning to turn into a Red Giant (This is because, the star runs out of fuel, and the nuclear fusion in the core stops…the core starts contracting under its own gravity…however this heats up the layer just outside the core, initiating fusion of hydrogen to helium…the higher temperatures causes the luminosity to increase manifolds…and the outer layers begin to expand causing the surface temperature to fall considerably and the visible light output shifts towards the Red end of the spectrum).
Its not safe for us to stay close to this star anymore because it is going to swell up like a balloon. The star’s diameter might increase hundreds of times during this phase. Our Red Giant star will also become very bright.
So Better wear your Sun glasses!!!
This cloud of gas and dust is called a Nebula. Once this molecular cloud acquires sufficient density of matter, it starts collapsing under its own gravitational force. Now move forward in time because this period of gravitational contraction is going to last atleast for the next 12 million years. During this time, the pressure inside this dense ball keeps building up and its temperature slowly increases. This heating up of the contracting matter causes it to glow, forming Protostars. So, at this point of time we can see the first traces of light. When the temperature of this cloud reaches 15 million degree centigrade, the nuclear fusion of hydrogen to helium starts at the core and the star enters its main sequence.
Say hello to our New Born Star!!!
Do you know that a star dies eventually after a period of time?? It was previously thought that stars are static and do not change with time. But observations have shown that stars do change and undergo a complex life cycle. The life cycle of stars can be compared to that of a human being – like humans, stars are born, live for a very long period of time and eventually die. However, the lifetime of a star is exceptionally long compared to human standards. So it is not possible for us to witness the life cycle of an individual star. But astronomers have come up with an ingenious method to solve this problem.
By studying different stars in various stages of development, they are now able to determine the various changes that a star undergoes during its life cycle. Ultimately, it is the star’s mass that decides its fate.
Scientists have divided the life cycle of a star into the following stages:
Stages compared to that of a human being:
· Protostar - Fetus
· Main Sequence – Infancy to Adulthood
· Red Giant – Middle Age
· White Dwarf / Black Hole – Old Age
The Sun is in its main sequence which started 4.6 billion years ago. Unfortunately, we won’t live to see the sun turning into a Red Giant as it will remain in this phase atleast for the next 5 billion years.
