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July 24, 2007


Robert Speirs

Consider that the light from different stars which makes up that image left those stars at different times, corresponding to each star's distance from Earth. We have no idea what the galaxy looks like right now, because the light leaving most of the stars today won't reach us for many thousands of years. Not only that, we don't even have an image of how the galaxy actually looked at any one time ever. I wonder if such an image could be constructed using available information. The posted image could be likened to a high school graduation group photo which shows some students at the age of 18, others at 65, still others as babies and which leaves some out.


Well, the diameter of the galaxy is on the order of 100 000 light years. The time scale of stellar evolution is measured in 100s of millions, so most of the stars in the image still exist now, and few new ones have come into existence. Stellar proper motions are fairly small, so the patterns have not changed much, either.

It's more like a yearbook which shows all 4 years together.

Ed H

I believe you are mistaken. The "view from the bridge" of a ship _approaching_ the galactic center at relativistic speeds would be shifted towards the other end of the spectrum. Instead of an infrared view, the occupants would enjoy a view where all wavelengths are shifted towards the ultraviolet.response


That's what it says -- at a blue shift of 2, the scattered visible light concealing the galactic center would be blue shifted into ultraviolet invisibility, and the .~1.2 to 1.5 micron band shown would span the red end of the spectrum as shown

Health News

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