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Not all galaxies are spiral, there are elliptic and irregular shaped ones also. Search for them on Google and images abound of non spiral shaped ones. A more interesting question is: why are galaxies, in general, laid out in a flat plane, like a dinner plate? According to studies dating back over 40 years ago, spiral galaxies are gravitationally unstable ...


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In the search by parameters screen you'll notice you can set limits on the morphological type. The types are given names, but the limits are input as though they are ordered. A little experimenting confirms the numbers you see reported as "type" correspond to the limits options, in the order of the drop-down menu. That is, we have: -3: dS0 5: Sb ...


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I agree with what BowlOfRed said, but I'm going to give an answer with a different nuance. So why is the night-sky dark rather than uniformly painted at the brightness of an average star? Because the universe isn't infinite. Big bang cosmology describes a universe that started small some 13.8 billion years ago and has been expanding ever since. It's been ...


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Olbers’ Paradox says that in an infinite universe every line of sight will end on a star. That statement is incomplete. The paradox requires not only an infinite universe, but also one that is both static and infinitely old. Neither of the second two statements are true for our universe. Your question considers the effect of aging. As our position ...


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It all depends on the closest approach of any stars to the Sun. When galaxies collide it is not that their stars crash into each other, because their individual cross-sections are extremely small when compared to the space between them. This is dealt with in qualitative terms on the wikipedia page on the likely collision. The Milky Way disk at the ...



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