Having examined the queer and tumultuous circumstances under which galaxies were formed, we shall next see what type of galaxies there are and try to reason out why they belong to one type or the other.
But first the post-Big Bang universe. Briefly!
After the Big Bang, matter was blown in all directions at furious and maddening speeds, perhaps rivalling the speed of light (which is about 300,000 km per second). Soon, however, this speed slackened considerably. Within the very first second the highly turbulent universe was not the same either in intensity or ferocity as it had started out.
Although light had not come into being yet, it required for the shredded matter to coalesce (i.e. gather into lumps) in billions of locations before the first rays appeared. The earliest light was created when the pristine (first) force of gravity and pressure led to the birth of the earliest stars (proto stars, let us call them) and the rapidly increasing heat led to eventual fusion of hydrogen atoms into helium on a mass scale to give the universe its earliest stars, and galaxies, which we shall discuss in detail at a later stage.
And with a billion stars suddenly glowing, the universe lit up. The party was on! Light was after all “invented”!
Most astronomers miss an important point at this critical stage of creation: why was it dark in the first place? Why would it take a considerable period of time before the first streaks of light appeared (with light from the earliest stars)? After all, the pre-Big Bang contained nothing if not crushed galaxies and stars. Then, the Big Bang itself could not have taken place without a lot of fire, heat, light and noise, as all explosions tend to.
To this postulate of mine they make an interesting observation: they say that when all matter (galaxies that is) came to be “housed” in a big region — all of them — then there was nothing “outside” the huge ball (discussed in the last column). So there was no uni-verse. Until then whatever light prevailed, it did inside the ball and nothing outside of it; it being not incandescent.
It offers an interesting study of how astronomers think and draw their conclusions!
I also think that while we agree that stars and consequently galaxies came into being as a result of intense pressure, why then did the matter inside the huge ball (before the Big Bang) not turn into one huge star? After all, the same forces were at work here (gravity and pressure) as inside the stars.
Let me hasten to add that if that had happened (one big star instead of hundreds of billions of galaxies and trillions of stars) then I would not have been writing to my friends, nor any of my friends reading it! So, it is better the way it happened!
Now the old question: which came first, the stars or the galaxies? It is no less than a paradox, for a galaxy is nothing if not a lot of stars (and much else too). It could not have come into being without the stars coming first, and then lending themselves obligingly to a gravitationally bound system. But some astronomers believe that some “humps” carried within them enough matter to cause a lot of stars that eventually came to populate a single galaxy; and then more and more came into being by the same method. With the passage of time (a billion, or a couple of billion years) the quasi (“almost”) galaxies assume the beautiful and ornamental shapes they now have (the “now” is half a dozen billion years!).
All galaxies have a nucleus, much as every fried egg has a yolk in the middle (yummy, eh!). So, the next time you munch on yolk, just imagine that you are eating the nucleus of a galaxy! The nucleus could be nothing but a large number of stars that came too close and were swallowed up by the little nucleus until it grew in size and became a super-heated “yolk” of the galaxy. In other words, the nucleus is stars in a “royal rumble,” one upon the other, inseparable, indistinguishable, thousands, nay, millions of them violently merged and mixed into one another so that they cannot be separated, having lost their identity forever (remember the pre-universe before the Big Bang?). Here, the atoms are not atoms and so there are no molecules. Maybe some nuclei have turned into black holes, thus obliterating any vestiges of the past. With different and to our view, queer laws of physics operating within the nucleus and close by. The discussion has veered into things altogether different so that I kept on the shelf all those things about the types of galaxies. But as you know, ideas in science have a very short shelf life so that we must discuss them briefly.
In all there are four classes or shapes of galaxies. We will discuss them briefly because their details will come our way from time to time in the course of our discussion in the future.
1) Ellipticals: These come in flying saucer or the fried egg shape, made up of old stars. These stars are clustered compact towards their centre.
2) Spirals: Perhaps the most popular, numerous and photogenic of all galaxies, such as our own — the Andromeda (M-31) galaxy. These may have big hubs (nucleus) or small hubs with arms full of stars jutting outward from the centre where they are thick but elongated and tapered as they extend. Each arm may contain anything from a few million to a billion stars.
3) Barred Spirals: May have just two major arms extending outward from the hub. Often the arms are thick but trail off. Each arm may have many billion stars.
4) Irregulars: Shapeless and unclassifiable galaxies. Most have a lot of turbulent gas clouds (nebulae, let us say) and even hot, brilliant blue stars. Some of these strange galaxies are low on gas and have old red stars. Irregulars may be thought of as the omelette that mummy makes on Sunday mornings.
So much for the types! Now, one big question remains to be discussed: is the Big Bang the only theory regarding the creation of universe? Plausible, though it may sound, yet it is not. Many scientists think differently (like many politicians do on any issue!).
In the next issue we shall ponder over the other theory doing the rounds for more than a hundred years. God bless.