Archive for the ‘Solar system’ category

Off on a comet!

11 December 2009

This post (hopefully first of a series) was inspired when a chance twitter about the Scattered Disc, Oort’s Cloud et al triggered requests from my Facebook friends to blog about the new Solar System.

The new Solar System

The mind can journey far beyond where the eye can see, or the ear can hear, and much much farther than the spear can be thrown.

The mind effortlessly soars beyond humanity’s farthest frontiers – the material frontier where Voyager now transits through the Heliopause some hundreds of millions of miles away – or the energy frontier – the outward traveling wavefront of the very first radio transmission recognisable as emanating from intelligent human life.

The position of Voyager 1 in 2007 as it approaches the heliopause. At the heliopause, the Sun's solar wind is stopped by the interstellar medium and the satellite is subject to the the stellar winds of the surrounding stars. (Click to enlarge).

The stars above me on a clear moonless winter night, the necklace of luminescent stars that make up the Milky Way, the pinwheel spiral galaxies where man may never reach – all these have fascinated me since I was a child. I adored fiction about space, especially space opera. Like most of us, for a long time all I knew was what I had learned in school – that we had a star and nine planets…yadda,yadda, yadda… Jupiter is the largest, Pluto is the furthest,,,yadda, yadda, yadda…

The old view of the Solar System - sun with 9 planets!

The old view of the Solar System - Sun with 9 planets, outermost of which was Pluto!

As a young child, I found nearby planets boring! I yearned for the deeps of outer space. I wanted to be on the bridge of the Enterprise, boldly going where no man had gone before. Galaxies were great stuff, so were pulsars and supernovas. Mars, Moon, Jupiter? Huh!

The Andromeda Galaxy portrayed on a German stamp of 1999.

I much preferred the mysteries of black holes and the looming terror of an event horizon to the rings of Saturn. It was during my early days of editing Wikipedia. I had not yet received a barnstar, a kind of award on Wikipedia. I learnt that if I reviewed five nominee articles for the status of ‘Good Articles‘ and shepherded them through a process, I was eligible to receive a barn star.

One of the articles I reviewed was Deep Impact (space mission)!  You probably would not have heard of 9P/Tempel – a minor periodic comet which circles around our Sun every five and a half years! A fairly frequent and predictable comet, it was selected by NASA as the first comet to be explored by their pioneering venture into space after comets – the unmanned space mission called ‘Deep Impact’.

While reviewing this article I once again discovered the magic and mystery in that mundane grouping of planets around a yellow dwarf that we call our Solar System.

Deep Impact, a spacecraft which sent an impactor to collide with Comet 9P/Tempel in July 2005.

Wikipedia tells us that –

A comet is a small solar system body that has a coma and/or a tail and is bigger than a meteoroid. When close enough to the Sun, a comet exhibits a visible coma (fuzzy “atmosphere”), and sometimes a tail, both because of the effects of solar radiation upon the comet’s nucleus. Comet nuclei are themselves loose collections of ice, dust and small rocky particles, ranging from a few hundred metres to tens of kilometres across.

Comets have long fascinated mankind – in the Western civilisation they have been regarded as harbingers of doom or omens of upheaval and change! The people of the past had no idea of geography, no concept of the Universe as we know it today. They found it fearsome to see a strange heavenly object appear amongst the familiar patterns of the constellations.

The tail of a comet always points away from the Sun!

This strange visitor moved from constellation to constellation and had a plume that ALWAYS pointed away from the Sun! For a period it would vanish as it would circle the Sun and reappear as a blaze on its return path. Gradually as it went into the deeps of space it would lose its plume, its shine and then disappear ostensibly forever.

No one could predict when such an apparition would return until the English astronomer Edmund Halley corelated historical data from a variety of sources and realised that in a cosmic game of Vikram and Vetaal, the comets of 1456, 1531, 1607, and 1682 were one and the same. He further predicted that this comet would return in 1758. Halley did not live to witness the comet’s return, but when it did, the comet became generally known as Halley’s Comet.

One of the earliest photographs of Halley's Comet taken during its visit in 1910.

Since then hundreds of comets have been mapped. Each year, large numbers of minuscule comets traverse the Solar system unknown to all but astronomers.

It is only those comets which are visible to the naked eye that draw the imagination of mankind. Such comets are called ‘Great Comets‘. Some of the recent great comets have been Halley’s Comet of 1986 which was visited by the Giotto space mission, Comet Hale-Bopp in 1997 and Comet McNaught in 2007.

On a gruesome note, members of a religious cult in the United States, called Heaven’s Gate committed mass-suicide after their leader proclaimed that a space-craft followed in the wake of comet Hale-Bopp to transport them to ‘the next level of existence’.

Besides this, Comet Shoemaker-Levy 9 made history in 2004 when it broke apart and crashed into Jupiter.

Comet Hale-Bopp seen over Croatia. It's arrival triggered a mass-suicide of the Heaven's Gate cult in the US.

But what is a comet composed of? What are the properties of its ‘earth’ or ‘soil’? To answer these and other such questions, many space missions have been launched to date. Vega 1 and 2, Giotto, Deep Space 1, Stardust and Deep Impact all helped us piece together what we know today.

To learn more about comets, read “Orbs of flame” (Part II), and for even more wait for ‘Deep Space and Stardust’ (Part III)…