Pluto is no more ...

a planet.

What!!! What happened to Pluto??

Hey don’t panic dude!! Nothing happened to it. I just said that Pluto is no more a planet.

Oh!! So, are you saying that we have got only eight planets??

Absolutely! According to the International Astronomical Union (IAU), we just have eight planets and three dwarf planets.

IAU?? What is this IAU?

IAU was formed to promote and safeguard the science of astronomy in all its aspects through international co-operation. This union unites all the astronomical societies in the world. It is also responsible for naming stars, planets, asteroids, other celestial bodies and phenomenon.

Ok, Fine! But why did they remove Pluto from our planet’s list??

There is a long story for that. In short, we can say that according to the new definition of planets, Pluto doesn’t qualify as a planet.

What is the new definition of a planet?

According to IAU, a planet must satisfy four properties.

1. It must orbit around a star or a stellar remnant.
2. It must have sufficient mass so that the self-gravity of the body can overcome the rigid body forces to become a hydrostatic equilibrium state.
3. It should not be massive enough to initiate thermonuclear fusion of deuterium in its core.
4. And should have cleared its neighborhood around its orbit.

Oh my god!! It’s very complex. Lots of astronomical jargon! Can u explain them clearly? What are the stellar remnants?

Stellar remnants are the remnants of star. They are three kinds - White Dwarfs, Neutron Stars and Black holes. They represent a final, end stage of evolution for stars. They are, in a sense, dead stars.

Ok! I got that. Now what about the second property of a planet?

Ha!! To explain that, I will plunge in to physics for a moment. A body is said to be a solid body if any of the external forces, however larger they may be, could not deform the body. Such a body is not possible to exist. So they came up with a concept of rigid body which is an idealization of solid body. In rigid bodies the deformation due to the external forces would be negligible. And the forces that do act against this deformation due to external forces are called rigid body forces.

I hope u know what the gravity is. A body’s gravity not only exerts force on other bodies, but also it exerts some force on itself and this force is called “Self-gravity”. And when the size of the body is very the large the self-gravity also becomes large. This large self-gravity will act opposite to the rigid forces and overcome them and try to pull all the points in a body towards center. And so it assumes hydrostatic equilibrium state (nearly round state).

Wow!! Then what about the third one?

Yeah!! I was coming to that. Nuclear fusion is the process by which multiple nuclei join together to form a heavier nucleus. It is accompanied by the release or absorption of energy depending on the masses of the nuclei involved.

Deuterium, also called as heavy water, is a stable isotope of hydrogen. The nucleus of deuterium, also called as deuteron, contains one proton and one neutron. I do believe that you know that a normal hydrogen nucleus doesn’t contain any neutrons. This deuterium can replace hydrogen in water and can form D2O (or heavy water). This heavy water is used as a coolant in the nuclear reactors.

Most of the celestial objects posses this deuterium. Even our earth contains abundant amounts of deuterium in its ocean beds. So is the case with other solar bodies. When the mass of the body is very large, the forces on the deuterium trigger a nuclear fusion and destroy all the deuterium in it and in turn release lot of energy. This force is called Gravitational confinement. And normally it is only possible in the objects as big as stars.

Ok! And the fourth property would be- a planet must have enough gravitational pull to attract all its neighboring celestial objects on to it and clear all its surroundings around its orbit. Am I right?

Absolutely Right!

So which properties did Pluto fail to achieve?

Pluto completely failed with the fourth property. It could not clear its neighborhood. Moreover, it has a highly eccentric orbit (eccentricity is the measure of deviation of shape from a circle). At times it comes closer to the Sun than Neptune. Pluto takes about 249 years to revolve around the sun out of which it will be close to Sun than Neptune for 20 years. And also, Pluto rotates in the opposite direction from most of the other planets.

Oho!! And that is why they disqualified it as the planet. So what is Pluto now?

Pluto is a dwarf planet. According to IAU, a dwarf planet is the one which satisfies the following properties.

1. It must orbit around Sun.
2. It must have sufficient mass so that the self-gravity of the body can overcome the rigid body forces to become a hydrostatic equilibrium state.
3. Has not cleared the orbit around its neighborhood.
4. It is not a satellite or any other stellar body.

The definition currently applies to only solar system. And so the first property says Sun.

Cool!! So do we have any other dwarf planets?

Yes! Apart from Pluto we have two other dwarf planets. They are Ceres

and Xena. Ceres is in the asteroid belt which is between Mars and Jupiter. And Xena is a trans-Neptunian object, which means it is far away from sun than Neptune.

Why have they made this resolution now? Why not before?

Pluto was discovered in 1930 in a fortunate mistake by Clyde Tombaugh. From then very little was studied about Pluto as it is very far from us. Actually that is the only planet (till 24^th august… now it is dwarf planet) where any of the man made satellites didn’t go. There were lots of controversies over Pluto and many of the scientists objected Pluto being referred as planet because of its high eccentricity, improper rotation access and many other features.

But the discovery of Xena on January 5^th 2005 has triggered the discussion. Xena is larger than Pluto and it is more eligible to become a planet than Pluto. This along with the Ceres has a few common features which are completely different from the planets. This results in categorizing these objects as dwarf planets.

So what our Hindu mythology says about the nine planets is wrong.

Absolutely wrong! Our Hindu mythology never spoke about the planets. The NavGrahas which they mentioned aren’t the planets. Doesn’t u remember Sun, one of the NavGraha, is not a planet. NavGrahas are the celestial forces that act on the man. That is why Rahu and Kethu (both the eclipses) were also there along with the other humungous objects in the solar system. To learn more about this, please check Anil’s blog.

Wow! That was really interesting.

Hmmm… Universe is always a very interesting topic and fascinates a lot of people. But the problem is most of us do not really care for it. This post is to just to educate a few. I hope to write more blogs on this topic.

γ-ray Bursts Contd ..

Yeah!! Ur guess was right. It met the same end.

Many believed in neutron star theory. But some didn’t. They argued on the basic observation that the rays are coming from all the different directions. This is only possible if our solar system is at the center of galaxy, which is not true. We all know that our solar system very near to the edge of the Milky Way and such a uniform distribution of rays is not at all possible.

But there is also another problem. If we believe that these rays are coming from different parts of the universe, then it means the end of Einstein’s famous equation. This is because none of the stars we see now could produce such an energetic γ-ray Bursts. Could Einstein be wrong???

May be….. But whole of our physics depends on his theory and if it is wrong, it would set a serious blow to the world of physics. But the fact still remains that the distribution of γ-ray are spread through out the galactic plane. So these rays are definitely coming from different galaxies. So is there an explosion which could break E=mc2???

To make sure that these γ-ray’s are coming from other galaxies, the best thing is to find out the star from where these rays are emerging from. γ-ray bursts doesn’t produce any visible light. But when γ-ray moves through the gas in the universe, they get heated up and lighten up. If we can get some such light, the suspense could be broken.

Very similar to a common day on which u are reading this, γ-ray bursts was picked up by the satellite and all the telescopes in the world are motioned in the direction of the rays. And Bingo!! They found a tiny hint of light.

Red-Shift is a mechanism that is used by the astronomers to find out the distance of the star from earth. The more red the star is, the more far it is. By using this red-shift mechanism they found that the rays are coming from 10 billion light years, at the edge of the universe.

This confirmed that the bursts are happening at different parts of the galaxy. Does this actually prove Einstein is wrong?

Probably No!! Martin Reese, a famous astronaut came to rescue. He proposed a theory which is very simple and fits perfectly in to the situation.

The basic assumption which we made was when ever an explosion occurs it sprays out the energy equally in all directions. According to Martin, this is not true. When a γ-ray burst happens, it sprays out the energy in a very narrow path in only two different directions. And hence the mystery was resolved.

But one question still remained!! What is the reason for these bursts?? Martin and many other scientists looked in to this issue and at last came up with a theory.

Stellar Nurseries is a place where stars are born. The normal age of a star is millions of years. But as the size of the star is bigger its life time also goes down. For example a star which is 100 times bigger than our Sun will not live more than a hundred years. Some stars are so big that they die in a few years after they were born.

But why do stars die?? Stars do require some fuel to burn. And for massive stars, considering it size, the fuel gets completed in a few years and they die. This is the reason for the death of the star.

Hypernova has been used to refer to an exceptionally large star that collapses at the end of its lifespan. The core of the hypernova collapses directly into a black hole and two extremely energetic jets of plasma are emitted from its rotational poles at nearly the speed of light. These jets emit intense gamma rays, and are the most candidate explanations for gamma ray bursts.

Many scientists are still experimenting about these bursts. And may be some day they can prove the reason behind these bursts. Lets wait for the day. :-)

γ-ray Bursts

“Stars” – probably the most important objects in the universe. These objects do create all the elements. The elements we see, we feel, we touch and we are made up of are all first created in stars. Learning about the stars is a very exciting thing. This post will help to understand about γ-ray Bursts and their relationship with stars.

γ-rays are very dangerous. Whenever a nuclear bomb explodes, it releases loads of γ-rays. These rays, when exposed to human body create a disaster. It burns up our cells, which are the basic blocks of our body. Our universe also creates such γ-rays in its course. These γ-rays from universe were discovered in an unexpected way. Some foolish thoughts do result in great discoveries. Such a thing has happened here.

That was the time of Cold-War between Russians and Americans. Americans were very worried about the growing nuclear power of Russians. Americans wanted to have a check on the nuclear tests conducted by the Russians. So they made a satellite to detect the nuclear tests. But the most foolish part comes up here. Americans know that Russians will conduct their nuclear test at some place where they least expect. And so, the most probable place they thought was “the dark side of the Moon” (J yeah very foolish). So they made their satellite “Sterling Colgate” so powerful that it would be able to detect γ-rays from large distances. And from these rays, they can calculate the energy produced by the bomb and hence the power of the nuclear bomb using Einstein’s famous “E=mc2” principle.

Sterling Colgate was launched and nothing was observed till one day. Normally whenever nuclear tests are conducted, it was observed that the satellite picks up two spikes in the graph, a small one followed by a large one. But on that day something different was observed.

There were a large set of spikes. Scientists thought that it was the satellite that was malfunctioning. But it wasn’t. It was something like five thousand nuclear bombs, as powerful as the one that fell over Hiroshima and Nagasaki, were exploded at a time. And these rays weren’t coming from the earth, not even from the moon, but very far from us somewhere in the universe.

Scientists and astronomers made a lot of observations and calculations and deduced that these explosions were very far from us but within our galaxy “milky way”. This was deduced from the famous Einstein’s principle.

Any physical activity that happens in this universe must abide to Einstein’s equation “E=mc2”. So if such an explosion occurs some where far in the universe and that ray’s reaches the earth, the explosion must be very big and so is the mass of the object which results in the explosion.

We know that the largest objects in the universe are “stars”. And none of the stars, that were observed till now, could be as big as the explosion reaches from one end of the universe to another. So from this simple logic, the scientists deduced that the explosions are from our own galaxy.

But what results in these explosions???

Scientists have also deduced a theory for that. They said that the culprit was “The neutron star”. The neutron star is the star that is reaching the end of its life. When the star is nearing its death, it swells up and it burns out all the fuel it has and then because of its gravity, it stars getting compressed. A star which is going through this phase of its life is called as a neutron star.

Neutron stars do have high density, heavy weight and so a large gravitational pull. So when some celestial particles do move near such stars, it pulls them with its magnificent gravitational power and results in a collision. This collision may trigger γ-rays.

This theory was proposed and was very widely accepted. But is this right???

Any physical theory is always provisional, in the sense that it is only hypothesis: we can never prove it. No matter how many times the results of our experiments agree with some theory, we can never be sure that next time the result will not contradict the theory. On the other hand, we can disprove that theory by finding a single observation that disagrees with the predictions of the theory. Earth was considered as flat until the Aristotle observed that during the lunar eclipse the earth’s shadow on the moon was always round, which would be true only if earth was spherical.

So has this “theory of Neutron star for γ-ray bursts” also met the same end??

Will be Contd in the next post....

The Primer

We go about our daily lives understanding almost nothing about the world around us. Most of the things were just taken as granted. We give a very little thought to the things that happen around us. Like, how many of us really wonder about the machine that is giving us the sun light which makes the life possible on earth, the gravity that is gluing us to the earth, the atoms of which we all are made up of and on whose scalability we fundamentally depend, the electrons because of which we are able to see the world at night, the massive dams which are for multi-purposes and many other wonderful things. These aren't the miracles that just happened in a day. Science is behind all these things. Normally in our society it is customary for parents and teachers to answer such queries with a shrug as they themselves are unaware of these things. And when the child becomes an adult he loses interest in querying about such things and takes every thing for granted.

These posts are just meant to answer some of such queries. Any comments and suggestions are welcome.