Why many galaxies, seen edge on, are extremely thin

[CLICK ON IMAGE FOR HIGH RESOLUTION, NASA, ESA, Hubble Legacy Archive; Processed & Copyright: Hunter Wilson]

Why is this galaxy so thin? Many disk galaxies are actually just as thin as NGC 5866, pictured above, but are not seen edge-on from our vantage point. One galaxy that is situated edge-on is our own Milky Way Galaxy.

EdgeOnClassified as a lenticular galaxy, NGC 5866 has numerous and complex dust lanes. … The blue disk of young stars can be seen extending past the dust in the extremely thin galactic plane. …

Although similar in mass to our Milky Way Galaxy, light takes about 60,000 years to cross NGC 5866, about 30 percent less than light takes to cross our own Galaxy.

In general, many disk galaxies are very thin because the gas that formed them collided with itself as it rotated about the gravitational center. Galaxy NGC 5866 lies about 50 million light years distant toward the constellation of the Dragon (Draco).


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