Whirlpool Galaxy M51
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Discovered over 200 years ago by Charles Messier, the Whirlpool Galaxy is probably the most observed and most photographed of all distant galaxies. And no wonder! Oriented almost perfectly oblique to our perception, its two clearly defined spiral arms are so elegant that galaxies of this type came to be called “grand design” spiral galaxies.
The remarkable structure and frantic star-birthing activity in the Whirlpool Galaxy are due to two powerful gravitational forces. One is a Black Hole in the center of the galaxy, whose presence has been inferred by observation of stellar matter emitting its last dying gasp as it hurtles over the “event horizon” — the point at which the force of the Black Hole is so powerful that light waves are stretched to infinite length, creating a sort of Doppler Effect. The second is a smaller galaxy that passed right through the Whirlpool, perhaps half a billion years ago, stirring up the interstellar dust with wave after wave of gravitational shock.
The star birthing areas can be clearly seen as bright blue areas in this spectacular Hubble photo, taken in 2005.
