<blockquote><font class="small">In reply to:</font><hr /><p>Malin 1, was found at a few hundred millions light year's distance is a real Monster with a <b>spiral disc</b> width of about 500, 000 light years across. Compare that to our galaxy of about 100K LY. If viewed from the same distance as Andromeda galaxy, it'd cover about 1/6th of the sky from horizon to horizon. But it'd be so dim, no one could easily see it. <br /><p><hr /></p></p></blockquote> <br /><br />Emphasis mine: Nice example, though it's not quite the irregular you imply. I do agree that there are a lot of dim irregular/elliptical galaxies out there. One reason they're overlooked is due to the selection effect common in astronomy (we see more big and.or bright things first).<br /><br />Anyway, Something about this struck me as off. The size is good, the distance fine (I kept misreading them, so that's my problem). Then it struck me, it wouldn't cover 1/6 the sky.<br /><br />The andromeda galaxy is ~150,000 ly across, and subtends ~178 arcminutes (the long way), or about 3 degrees (that's quite a bit!) of sky. So Malin1 is 5x wider, for a subtended angle of 15 degrees.<br /><br />That's about 1/12th of the sky. Larger than my gut feeling, but still satisfies my hunch that figure was a bit rough.<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>astrophysicists are sure beyond all reasonable doubt about why ....<p><hr /></p></p></blockquote> If you go by that standard, you'll have very little to talk about in this field.<br /><br />The density wave theory, basically the alignment of eliptical orbits, gives spiral structures stable in the required time frames, in computer models. It's quite successful in recreating the various spiral structures.<br /><br />We also have a pretty good idea how a lot of eliptical and spherical galaxies form: Mergers. Ones that didn't foster the left-overs to form into a disk (say a low velocity collission of two massive objects, comming at a "steep angle"). Some may have merely <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector. Goes "bing" when there's stuff. It also fries eggs at 30 paces, wether you want it to or not actually. I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>