I would just like to mention that for many of us brits there is one man that is larger than the sky, a national treasure Sir Patrick Moore http://www.youtube.com/watch?v=52fRJU7BA...re=related

(September 27, 2012 at 9:24 pm)jonb Wrote: I would just like to mention that for many of us brits there is one man that is larger than the sky, a national treasure Sir Patrick Moore

Indeed. Caldwell-Moore's work is well known to amateur astronomers. Notable amongst his work is the Caldwell catalogue of deep-sky objects.

While the Caldwell catalog consists of already-known objects culled primarily from the New General Catalogue, Moore compiled his catalog based on what was observable to amateurs using fairly modest instruments (and not already included in the Messier catalog). Once an observer has viewed all of the Messier objects (which can be done in one night), the Caldwell is a natural next milestone before taking on the Herschel 400.

This was important work - the NGC consists of nearly 8000 deep-sky objects (star clusters, nebulae, and galaxies), most of which are insanely difficult to impossible to observe with amateur instruments even from truly dark sky sites. From personal experience, I can tell you that even with a computer-aimed 250mm (diameter) telescope and a good star map under dark skies, hunting a piece of sky for NGC objects is an exercise in futility.

While astronomical catalogs list magnitude (brightness) for listed objects, deep-sky objects are extended, not point sources of light, and you can't compare the visual magnitude of an object vs. the limiting magnitude of your instrument and conditions to determine if an object will be visible. Caldwell's list consists of objects an amateur can likely see - if you can find them.

A collage of the objects of the Caldwell catalog:

I can't comprehend the fact that each one of those galaxies might be teeming with life. That is just...wow...

(September 27, 2012 at 11:37 pm)teaearlgreyhot Wrote: I can't comprehend the fact that each one of those galaxies might be teeming with life. That is just...wow...

And then, you follow up that realization with the fact that this image was taken by Hubble looking at just one tiny pinprick's width across the entire sky... that this is just one tiny fraction of a tiny percent of the whole thing. The original Ultra Deep Field from 2004 was one part in thirteen million of the entire area of the sky. I can only imagine that this image is of a smaller portion by exponentially greater proportions.

Feeling small?

(September 27, 2012 at 11:37 pm)teaearlgreyhot Wrote: I can't comprehend the fact that each one of those galaxies might be teeming with life. That is just...wow...

It is mind-boggling...

There are hundreds of billions of galaxies in the observable universe.

On average, each galaxy contains hundreds of billions of stars.

We have been able to detect extrasolar planets orbiting main-sequence stars for 17 years - and we are finding them in abundance. We've been able to detect lower-mass (presumably terrestrial) planets for only a couple of years, and we are discovering those in relative abundance as well.

It's estimated that on average, there are at least 1.6 planets for each of the 100 billion or so stars in our galaxy alone.

Even if only a tiny fraction of those planets are suitable for the development of life, there are likely to be millions of them in our galaxy alone.

If only a tiny fraction of those have actually developed life, there could be hundreds to tens of thousands of life-bearing planets in our galaxy alone.

Multiply that hundreds to tens of thousands of life-bearing planets by a couple hundred billion and imagine the possibilities.

I wonder what the chances of sentient life like us humans evolving is out there.

I hope for their sake they're nothing like us.

(September 28, 2012 at 12:14 am)teaearlgreyhot Wrote: I wonder what the chances of sentient life like us humans evolving is out there.

There's an app for that.

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(September 27, 2012 at 11:55 pm)Ryantology Wrote: And then, you follow up that realization with the fact that this image was taken by Hubble looking at just one tiny pinprick's width across the entire sky... that this is just one tiny fraction of a tiny percent of the whole thing.

Here's how you can visualize how small of a piece of sky the entire Extreme Deep Field image represents.

Take an ordinary marker pen. Make a dot on your thumbnail, perhaps 2mm in size. Hold your thumb out at arm's length.

The dot would just about cover the entire extreme deep field.

(September 28, 2012 at 12:14 am)teaearlgreyhot Wrote: I wonder what the chances of sentient life like us humans evolving is out there.

Probably not very great at all.

Think of the millions of species that have existed on this planet in the last 600 million years and the number that have developed a technological civilization, then extrapolate that to the universe at large.

I think that Life will be very common through out the cosmos, because life is really just a complicated chemical reaction. But intelligent species will be very rare and technically capable one even rarer still.