Companion
Decades ago, it was not known with certainty whether the companion galaxy NGC 5195 was a true companion, or another galaxy passing at a distance. The advent of radio astronomy and subsequent radio images of M51 unequivocally demonstrated the reality of the interaction.
Recent simulations bear out that M51's spiral structure was caused by NGC 5195 passing through the main disk of M51 about 500 to 600 million years ago. In this model, NGC 5195 came from behind M51 through the disk towards the observer and made another disk crossing as recently as 50 to 100 million years ago until it is where we observe it to be now, slightly behind M51.
Read more about this topic: Whirlpool Galaxy
Famous quotes containing the word companion:
“Ambition is an uncomfortable companion many times. He creates a discontent with present surroundings and achievements; he is never satisfied but always pressing forward to better things in the future. Restless, energetic, purposeful, it is ambition that makes of the creature a real man.”
—Lyndon Baines Johnson (1908–1973)
“A soul that makes virtue its companion is like an over-flowing well, for it is clean and pellucid, sweet and wholesome, open to all, rich, blameless and indestructible.”
—Epictetus (c. 50–120)
“I have found it a singular luxury to talk across the pond to a companion on the opposite side.”
—Henry David Thoreau (1817–1862)