"He ate and drank the precious Words,
his Spirit grew robust;
He knew no more that he was poor,
nor that his frame was Dust." -Emily Dickinson
When we look at spiral galaxies, we think of grand arms, star-forming regions and dust lanes lining our perspective. But unlike face-on galaxies, where everything looks the same, galaxies that appear tilted at an angle often appear to have one half far greater in its dust-richness than the other.
This was regarded as a mystery for a long time, but the recent Pan-chromatic Hubble Andromeda Treasury (PHAT) survey confirmed the leading picture: that the dust lanes are confined to a narrow, central region of the disk, and the dusty appearance is an optical illusion. It’s a simple result of perspective, that more of the brighter stars are hidden behind the dust from one side than the other.