BEFORE I begin to conclude my discourse on inter-stellar matter, also called the dark matter, lying sprawled between the vast, empty/vacant spaces within individual stars, let me quote verbatim the following words from a master astronomer/physicist/writer:

“There is probably no more fundamental mystery in science, or in human imagination, than the nature of the origin of the Universe. As self-awareness dawned in the first of our species, a growing puzzlement about Creation must not have been very far behind. As puzzlement gave way to wonder, and wonder to reason, human civilisation remained obsessed with trying to understand how all we can see came about.”

Lawrence M. Krause; in the essay, Rediscovering Creation.

I feel sure that by now you too, my young friends have developed the trait and mind for thinking deeply over the mysteries of creation and of nature. The more the puzzlement on the issues of science the more questions you will ask and the more you will be rewarded eventually.

Back to the inter-stellar matter: many remarkable astronomers, with the addition of at least one great observer of the skies, almost became victims of the studied indifference of some establishments that ran the astronomy affairs of their respective observatories way back then. The findings of our great friends on the interstellar matters were treated with disdain.

Henry Norris Russell (1877-1957 ), who went on to carve a name for himself in the annals of astro-physics and cosmology, was among the first to confirm that the matter comprised fine dust stretched between stars, often several light years across. Dust grains, actually huge molecules made up of millions of atoms, which exist as diffuse clouds all over the galaxy.

Occasionally, the clouds gather to form bigger ones and collapse under the force of gravity to form new stars, usually in groups known as clusters. While this happens, some of the gas and dust is ejected back into space where it rejoins tenuous clouds.

When a star dies, yet another bout of mass ejection takes place and the process is repeated all over again. What a comical departure from the earlier assertions of some astronomers who denied that interstellar matter had anything to do with star formation!

As you well know that in the early universe all matter was hydrogen and helium; little else save these elements.

The two are perpetually stirred, mixed and churned inside stars where the gas portion is percolated after being cooked and cooked again, and ejected back into space by stellar winds.

Millions of years later, the matter changes its chemical composition, evolving into higher proportions of heavy elements besides. With the passage of astronomically long time these coalesce into solid dust grains which end up obscuring starlight. It is also the raw material for the gradual accretion leading to star/planetary formation.

So much for the overzealous astronomers!

Our Sun, Earth and all planets and their moons were formed from such interstellar junk. Earth is a highly condensed matter, both gas and solid dust, further processed in the Earth’s core, on its surface and oceans. The core of the Earth is heavy iron, the outer layers are lighter elements and the atmosphere is light gases. All of this matter gelled together in interstellar space and became the Solar System. It took about 500 million years for it to take shape.

Interstellar matter forever rains down on our (and other) planets depositing no less than 10,000 tonnes of material everyday on our hapless planet (for the uninvited pounding it receives from outer space).

The billions of comets and meteors are a signature of the leftover debris and tell a full tale about how stars and planets came into being, slowly yet inexorably.

Occasionally, these rain down across the inner Solar System to be visible to us as cascading little pieces of accreted material. Now you know that everything in the outer space is subject to recycling. Old ones are churned into new ones, and so on. Thus, it is largely incorrect to say that the interstellar matter or the dark matter is just lying in a heap and doing nothing. It is another matter that it “seems” to be doing little in the time it takes for a few life times to observe them and for the space or the cosmos it is about millions and billions, whether years or miles or whatever else for it is a micro as well as a macro affair.

Summarising the interstellar matter, we may conclude our findings as follows:

Interstellar space is vast and apparently empty space, having been truly understood only in the last about 100 years.

The clouds it is comprised of are enormous (often many light years across). These consist of molecular hydrogen gas and a tiny portion of heavier atoms and molecules such as calcium, sodium, water, ammonia, formaldehyde and carbon monoxide.

It also contains a large amount of microscopic solid dust particles as well as magnetic fields which thread its way around stars. For our Galaxy it is only five per cent of the total mass. This means that a noticeably small amount is covered by interstellar matter.

In my reckoning it appears too little. The actual percentage is probably much higher but nowhere near the 90 per cent as predicted by many cosmologists. I do not doubt any foul play on their part but a display of chagrin and over zealousness.

Whatever the portion of dark matter in our own Galaxy should be true for all of them, especially the spiral galaxies. Goodbye and God Bless.