Is there a way perhaps to tell which objects are closer in the foreground on this? maybe by picking up the intensity of the light perhaps.

While we can measure the intensity of the light from each object, that does not allow us to tease apart distance and intrinsic brightness. We know that stars vary over a huge range of light outputs. But most of the brightest naked-eye stars are quite a distance away (hundreds of light years in most cases, IIUC).

Measuring distance is a real challenge in astronomy.

The closest objects can be directly triangulated using their parallax shift (apparent change in position against the background of more distant stars over the course of the year as Earth moves from one side of the sun to the other). Some stars give us clues, because we can infer their intrinsic brightness from other properties (look up Cepheid variables on Wikipedia).

There are several techniques used, and the uncertainties get larger with larger distances, but we are able now to infer a measurement of distance for the most distant galaxies based on their red-shift (recession velocity).

“Galileo wasn’t the first to turn his telescope to the sky, nor was he the first to record what he saw.”

I’m curious what your reference for this is. I dabble in teaching the history of science, and have a particular fondness for Galileo. Conventional wisdom is that he was indeed the first to create a telescope that was good enough for astronomical research, and the first to use one in that way. It was less than a year between the invention of the telescope and when he began his observations for Sidereus Nuncius (and less than a year after that it was published). He had contacts close to the original telescopes to feed him info, and most educated people of the time though the whole telescope thing was nonsense until they saw one (persistent myths of such things had been around for thousands of years).

It’s stuff like this which makes me unable to fathom some people who are so earth-centric that they fight over religious differences and don’t believe in the benefits of space exploits.

There is so much more to life than just fighting, shopping for the latest Ipod and not caring who you screw on your way up the corporate ladder.

Reminds me of a famous quote from Katherine Hepburn that went along the lines of “Human nature is the one thing we are put on this Earth to rise above.”

Incredible how we’ve gone from Galileo to Hubble, et al. (Yes, they seem like people-machines.) Can you imagine what Galileo would say? Probably the same kind of excitement he must have had then…everything is relative to the times.

Thanks for the information.

I have to admit that it sounds better than “the arc of an arc-welder”.

Why not assign a _band_ of color within the visible spectrum to each? I would have thought that that would make a much prettier picture.

Because that is more likely to obscure detail than to illuminate it.

Let me explain:

Our visual system operates with only three peaks of wavelength-sensitivity. These wavelengths correspond to the colours we call red, green and blue, but in fact red and green are much closer to one another in wavelength than either is to blue. Where a photon has a wavelength that is between the peaks, it activates both photoreceptor types (actually, a single photon cannot activate your colour-sensitive cone cells, which is why we lose colour vision at low light levels, but consider a stream of photons instead) and we perceive an intermediate colour. This is the rain’s way of interpreting that mixed signal.

However, if you have a stream of photons that are monochromatic and between the red and green peaks of sensitivity, we perceive that as yellow, but we also perceive as yellow a light stream that has an equal mixture of red and green photons (by which I mean photons with wavelengths that correspond to our perception of the colours red and green). This effect is how TV and computer screens generate a many-coloured picture out of just three colours.

Now, back to the NASA pic.

Because the three types of spectrum have each been assigned a single colour, we can see additional detail where those colours mix and produce (for instance) yellow or white light (or, more specifically, a mixture that we perceive as yellow or white). This mixing stands out from the image.

Now, if each waveband had been assigned a portion of a continuum of light, we would not be able to pick out areas that are bright in both the far- and near- IR, or areas where X-ray sources are mixing it with dust clouds. These mixtures would either appear too close to one end of one of the two contributing wavebands, or they would appear to us as a colour that is plentiful elsewhere already. It would be harder for us to interpret the image.

D’you see?

Now, why did they choose blue, red and yellowy-orange instead of blue, red and green? Probably to represent as best they could the actual wavelengths involved. The red is the far-IR; yellowy-orange is the near-IR; and blue (being the shortest visible wavelength and slightly closer to actual X-rays than any other visible wavelength) is X-rays.

I has a new desktop background

(Pretty sure Wikipedia is fairly good and reliable here.)

@ 16. mastmaker Says:

I know I am being tangential kinda here. But this has been bothering me for quite a while now:

We are located towards the outer edges of (one of the arms of) Milky Way here, right? And when we look towards the center of the galaxy, we see the bright center of the galaxy somewhat obscured by enormous dust clouds, right? So we cannot observe what is beyond Milky Way in that part of the sky. And strong radio sources within our galaxy hinder exploration of that region with radio telescopes as well. So, we will not figure out what is there in that region for at least next few millenia until we revolve around the center of the galaxy enough to bring that region to our view. I mean, there may be one or more nearby galaxies (even within local group) and we don’t know it, right? Or am I being a simpleton, here?

No, you are not being a “simpleton” at all – good questions and comments there. I’ll run thro’ them quickly as I understand them:

We are located towards the outer edges of (one of the arms of) Milky Way here, right?

Yep. About two thirds of the way out from the centre or 25-30,000 light years~ish in the Orion spur if memory serves. (Exact figures may vary from source to source, I think.)

And when we look towards the center of the galaxy, we see the bright center of the galaxy somewhat obscured by enormous dust clouds, right? So we cannot observe what is beyond Milky Way in that part of the sky. And strong radio sources within our galaxy hinder exploration of that region with radio telescopes as well. So, we will not figure out what is there in that region for at least next few millenia until we revolve around the center of the galaxy enough to bring that region to our view.

Yes, the heart of the Milky Way is, indeed, obscured by dust at some wavelengths – esp. visible and radio. UV, X & Gamma rays can pass right through – I think but might be wrong there.

I mean, there may be one or more nearby galaxies (even within local group) and we don’t know it, right?

Yes but we are finding more and more of these hidden dwarfs all the time. The Saggitarius dwarf elliptical* was detected even despite the obstacles along with a number of others** and I think we’ll probably still find more.

* See http://en.wikipedia.org/wiki/Sagittarius_Dwarf_Elliptical_Galaxy

** For example, the Canis Major dwarf galaxy see : http://en.wikipedia.org/wiki/Canis_Major_Dwarf_Galaxy

@ 14 Coolstar :

Gotta say i’m pretty underwhelmed (more so because of all the pre-release hype): aesthetically, this doesn’t really compare to lots of other images . NASA’s PR department, even after decades, still just doesn’t quite get it.

I disagree with you on both counts there. You’re really not impressed with this panorama? Well, whatever floats your boat, mate but it sure impresses me. I find your comment there a bit sad really & I’m not sure I get whatever point it is you think you’re making with it.

This is a snapshot of our Galaxy’s core 25,000 years ago for that’s about how long it takes light (& other forms of electromagnetic radiation) to travel from there to our eyes here on Earth.

I wonder what its like now & whether the gas has shifted and any of the stars blown up?