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[Chicago Astronomer - Astro Joe]

Cartwheel Galaxy Makes Waves In New NASA Image

This false-color composite image shows the Cartwheel galaxy as seen by Galaxy Evolution

Pasadena CA (JPL) Jan 12, 2006
A new image from NASA's Galaxy Evolution Explorer completes a multi-wavelength, neon-colored portrait of the enormous Cartwheel galaxy after a smaller galaxy plunged through it, triggering ripples of sudden, brief star formation.
The false-color composite image shows the Cartwheel galaxy as seen by Galaxy Evolution Explorer in ultraviolet light (blue); the Hubble Space Telescope in visible light (green); the Spitzer Space Telescope in infrared (red); and the Chandra X-ray Observatory (purple).

"The dramatic plunge has left the Cartwheel galaxy with a crisp, bright ring around a zone of relative calm," said astronomer Phil Appleton of the California Institute of Technology, Pasadena, Calif.

"Usually a galaxy is brighter toward the center, but the ultraviolet view indicates the collision actually smoothed out the interior of the galaxy, concentrating older stars and dust into the inner regions. It's like the calm after the storm of star formation." The outer ring, which is bigger than the entire Milky Way galaxy, appears blue and violet in the image.

Full story here: www.spacedaily.com/news/Cartwheel_Galaxy_Makes_Waves_In_New_NASA_Image.html

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I wonder...

What it must have been like to any inhabitants of that galaxy when the other body smashed through. Planets torn from their suns, debris orbits plunging in toward stars and the sky full of rapidly moving objects.

Scary!...

[Maddad]

Those inhabitants probably were totally unaware of the collision. The timescale would have been so large that their entire civilization would have risen and fallen with no measurable movement in debris.

I tried to find some Hubble pics of the Cartwheel. APOD took shots at it a long time ago, February 24, 1997 ( antwrp.gsfc.nasa.gov/apod/ap970224.html ) and 2001 June 12 ( antwrp.gsfc.nasa.gov/apod/ap010612.html ). There were a couple of others, such as one the following day, but these are not the big, high resolution images that we have become accustomed to. I'll keep my eye out for a good Cartwheel shot taking just recently. It ought to be spectacular.

[Chicago Astronomer - Astro Joe]

Agreed that the time line for such events is quite long, but a civilization could be at any point of their development during any stage of the event - be it crawling out of primordial slime or harnessing suns.

There has to be an noticeable occurrence to someone...(if anyone was there), even if they did not understand what was going on.

Grasshopper...If a galaxy smashes through another galaxy and no one is there to hear it, did it really happen?...

[Maddad]

Depends on whether there was a smash or not. Probably no two stars will collide.