I'm not a scientist Chris but I read a lot and Astronomy has been a lay interest for me for over five decades. Further I try to keep up with scientific articles on how life developed here on Earth, how hard it was to be created and what chance that it could develop elsewhere.

In the end you may be right, but I suspect not. And that's not just whimsical thinking. One of the flaws in human thinking is the belief that we are in some way special, unique, a once off. We, in our arrogance (and that is not meant as disrespect for you but rather as a species), have throughout our history, especially since we have become increasingly urbanised and separated from nature, that we are 'God's or the Gods' sole purpose for creation. It has infected our thinking even despite time and again scientific revelations have shown we do not hold a special place in creation.

Our planet is not the centre of the universe, it is not the centre of the solar system, it is not the centre of the galaxy, it is not the centre of the Universe (well that depends on perspective that one if you consider everything is the centre). Humanity didnt develop on the 6th day of creation, we didnt even appear until life had been here at least three and a half billion years and our tenure on this planet may be one of the shortest of any species if we continue to be arrogant about how special we are.

According to my reading life occurred spontaneously on this planet, perhaps many, perhaps dozens of times. The early Earth was too unstable to maintain conditions conducive to life for lengthy periods. But eventually it seems to have held.

The general scientific opinion is that life, because of the simplicity of elements required and the effectiveness of carbon molecules to achieve increasing complexity, occurs spontaneously and seems to be an integral component of the Universe, just as planets and stars are. Of course greater complexity brought about by aerobic life forms, the development of bisexual systems etc are seemingly much harder to achieve but once achieved, life exploded into a huge range of variations.

True intelligence is not the aim of evolution but it does seem to be a prefered element for survival, so increasing intelligence is not to be unexpected. Certainly humanity's position of being self aware and to be able to dream of things that dont exist in nature is also a major step forward and probably very rare.

But life seems to survive everywhere. Not because I want it to be there, but I suspect some form of life will be found elsewhere in the Solar System.

Now getting to the Alpha Centauri system, and I'm on more secure grounds here because of my reading and interest.

One of the arguments for life elsewhere, and a life that can get beyond simple bacteria and fungal systems, in the Universe is that it may require conditions similar to what we have here on Earth. That means a similar sun, a star that is metal rich, a star that is mature enough to have allowed life systems time to develop, a planet in the Goldilocks zone where water can exist in its three forms, a planet massive enough to hold a substantial atmosphere (not necessarily oxygen based...anaerobic life forms can exist without pure oxygen and as you know expel oxygen as a by product..further oxygen easily combines with other elements such as iron and once that has occurred molecular oxygen can exist almost indefinitely in the atmosphere) and a planet that is relatively stable in a reasonably circular orbit and revolution and isnt disrupted too often by external forces.

So lets look at the Alpha Centauri system.

We firstly ignore Proxima Centauri because it is a red dwarf and 1/5 of a light year from the primaries.

We are left with Alpha Centaurus A and B which orbit each other in an elliptical orbit a distance from each other as the Sun is to Uranus and Saturn..That has been the only question mark about this system, the capacity to hold planetary systems, because of the gravitational effect the two close stars have on each other and objects in orbit about each. It wiped out gas giants fairly quickly.

But close orbit Pluto to Earth sized planets were always deemed a possibility. The discovery of an Earth sized planet, albeit in a very close tight orbit around ACB, vindicates that belief. Planets can apparently exist within about twice the distance from Earth to the Sun around both stars....maybe a little less around ACB. So an Earth sized planet around at least one of these stars in its Goldilocks Zone is very possible if not probably. That was the only hang up about the AC system.

The rest is easy. Alpha Centauri A is almost an exact match for our sun. A little bigger but very close. Chances of the closest star being a G2 star like ours are at least 100 to one. G stars are only one in twenty of the stars in the Universe and there are ten levels of G stars from the hottest G0 to the coolest G9, which is what Tau Ceti is, the closest single G star at 12 light years away.

Alpha Centauri B, around which this planet has been found is almost a G star. Its the next level of stars cooler but its K1, only slightly cooler than Tau Ceti and still capable of holding an Earth type planet about as far out as Venus is from the Sun, which would be in its Goldilocks zone.

Further positives are that the Alpha Centauri system is actually more metal rich than our Sun which suggests it has all the elements and in larger supply to build planets and life. Further it is about 5-6 Billion years old and therefore older than our Sun (4.5 billion years) and therefore has had a greater time, as long as the planets have maintained stability, to have established at least basic life many times over and possibly more complex life that we will be able to easily recognise.

If life is as spontaneous as it seems, and given an earth type planet has been found orbiting Alpha Centauri B, albeit in the too hot zone, this discovery I believe will have profound implications in respect of seeking life elsewhere in the Universe. It is now very possible that we have neighbours, perhaps micro organisms but perhaps also far more complex.

I don't think that life is what this article is about. Save for the last paragraph which I interpreted to mean "it'll be exciting when we find a planet that we might actually be able to live on," which is not an entirely unreasonably expectation (a planet like earth might be extremely rare, but if it happened once... why can't it happen again?). This article doesn't suggest that life cannot possibly exist on a planet not like earth (albeit, it does suggest the Alpha Centauri Bb is too close to its sun to support life, but this is possibly more of an assumption than a logical fallacy, and one made knowing that it's probably a planet that we can't live on).

I suspect, Terry, he was talking about life like our life.

Almost assuredly there exists life of a different nature (excuse the pun) out there. And we already know of different life forms here such as anaerobic life and who's to say prions arent another form of life.

I was certainly being conservative in my response, but it could be that life is teeming elsewhere in the Universe and that if we scratch beneath the surface of Mars or go skinny dipping in the underworld oceans of Europa, Ganymede, Callisto, Titan and perhaps Triton, just to name the obvious ones, that a form of life isnt existing there. Then there's the clouds of Jupiter, Saturn, Uranus and Neptune, rich is elements that could give rise to a constantly floating life form.

Maybe even Venus has a particularly resilient form of life able to survive that toxic metal melting,high pressure atmosphere (we've been gobsmacked regarding where we find life on Earth of late).

Of course I'm letting the imagination flow unrestrained but then perhaps I'm still being limited and conservative. But I suspect if equines are found on a planet in the Alpha Centauri system, they will be horses of a different colour..

[url=http://www.express.com.pk]Go[/url]
<a href=http://www.express.com.pk">News</a>;