What are those bars of darkness on xray view[0]? I suspect it's an artifact of stitching photos together rather than a real phenomenon, but I'm curious about the real answer.
My favorite of the wavelengths presented is radio, as right in the middle you see a bright radio source that I'm guessing is Sagittarius A, (probably) the location of the Milky Way's supermassive black hole.
The definition of "real" that first jumps to mind is how closely the image reflects the mass of the bodies in the galaxy, but I also wonder if there are other thought-provoking definitions?
An interesting question! If it's mass you're after, you need to consider that different wavelengths trace different condensations of mass. Here are some examples that follow the mass of stars in different evolutionary stages:
1) In visible light, you can pretty easily deduce the masses of the stars if you correct for their light shifting to red as it passes through interstellar material. As the star spectra often peak in optical wavelength, the optical image is the "realest" for the star mass
2) When the stars have just been formed, they are still obscured by what we call dust - tiny micron-sized carbon-core particles that are annoyingly good at absorbing optical light. The best tracer for this mass regime would be infrared light, since the dust allows for some transmission.
3) Before the stars are formed, their mass resides in a diffuse (more so than any vacuum in our science labs) yet massive (10^3-10^7 solar masses) molecular clouds. They are typically very cold (~20 K) and their emission peaks at far-infrared light.
They are all "real" and very useful in different ways. Its important to remember that they are all maps of different thing depending on how transparent the things they are mapping are. For example the dark clouds in the optical are nearby cold / dense clouds of gas where stars are forming. They block almost all the visible light from the stars behind them. If you want to study star formation (my PhD) you can learn a lot by looking at how they absorb light, or you can look at a different wavelength and look inside / through them (microwave).
You have to remember that the maps are measuring how bring sources are (at each wavelength) filtered by how absorptive the stuff along the line of sight is (at each wavelength). In the same way that images of far away galaxies are looking back in time, images at different wavelengths probe different distances and temperatures in our galaxy, but in a much messier way.
I'm not astrophysicist, but I would think they're all as real they just give different information about the underlying structure and events of the universe.
Perhaps a the question should be, "which wavelength is more useful?"?
A lot of the bright spots in the gamma ray image are supernova remnants (pulsars and blazars). You can sometimes see the gas from the explosion emitting in H-alpha around the pulsars (like near vela). Pretty cool.
My takeaway is that the galaxy is a much flatter disk than we think based on classic pictures of the milky way. The clouds that make it seem fat are just nearby rubbish, and the other wavelengths reveal there's nothing really there.
Can someone explain the dark streaks in the x-ray spectrum? (Edit: question is answered below -- they are gaps in observation, not actual dark streaks.)
Awesome, thanks for making this! Any plans to update the URL hash so a current view can be shared with a link? I would think it wouldn't be too difficult since there are only a handful of variables. I (and HN) would be glad to contribute if desired.
I wonder if this says more about our sensor technologies than how the galaxy actually looks (the visible, infrared and microwave images look far richer than the others).
> I wonder if this says more about our sensor technologies than how the galaxy actually looks (the visible, infrared and microwave images look far richer than the others).
There are definite effects from technology. The radio and far-infrared observations are at much lower angular resolution than the optical and near-infrared, for example. So there's less spatial detail in those. Also, some surveys have been carried out in more than one filter/color (e.g., optical, near-infrared) and so the optical image shows some information about the color of objects in the optical. In contrast, the radio image appears to be a single frequency, and so doesn't contain that information for the radio sources.
However, there is a lot of information there about the galaxy. The distribution of sources, for example – you can see the well-defined disk of the galaxy in all bands. The dust lanes corresponding to gas clouds are apparent in the optical as the dark patches. You can also see that there are some sources which emit brightly in X-rays, but are not seen in the other images. So that tells you about the types of objects in the galaxy.
So, despite the fact that the technology affects the images, I would not say that the map says less about the galaxy than about the technology.
It would be awesome to see a separate grayscale (or at least same-color-gradient) image at every wavelength they’ve recorded, with color scaling based on radiant flux and consistent across images. (Could be log-scaled or whatever if some of the images would otherwise be too dim.)
Even better would be to show a large chart of all those images at once, so they could be compared on a large display without needing to scrub a slider back and forth.
With these false color images, it’s impossible to know without careful investigation what the colors in each image represent or how they’re mixed together, and it’s impossible to make useful comparisons.
> Even better would be to show a large chart of all those images at once, so they could be compared on a large display without needing to scrub a slider back and forth.
See the "Multiwavelength Milky Way" poster from NASA: http://mwmw.gsfc.nasa.gov/mmw_product.html#poster
They're still false-color and only show the plane of the galaxy, but you can at least see them all simultaneously.
Very cool. It would be interesting to rework the slider as an RGB channel mixer that slides different observational wavelengths across the monitor's color channels, instead of just blending between images.
Repeating solaris999's comment above:
The "What am I looking at?" section (http://www.chromoscope.net/1.4.1/what.html) says that they are:
"Don't worry, they aren't holes in the Universe being ripped open by creatures from another dimension! They are actually just gaps in the survey."
If I take the time to complain, it's because I don't have access to a computer, and that I believe the website's devs could improve it. I do believe they didn't test it with Firefox. It's all Webkit these days. :B
[0] - http://imgur.com/a/63tJD