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:
“I endeavor not to conceal that I believe there is a great mixture of desire in the passion which is called love—or rather, without any far-fetched strain on words, it may be called the companion of love.”
—Sarah Fielding (1710–1768)
“I never found the companion that was so companionable as solitude.”
—Henry David Thoreau (1817–1862)
“Guilt is perhaps the most painful companion of death.”
—Elisabeth Kübler-Ross (b. 1926)