M51 - The Whirlool Galaxy
Credits: Keith Turnecliff, Long Itchingrton
The graceful, winding arms of the majestic spiral galaxy M51 appear like a grand spiral staircase sweeping through space. They are actually long lanes of stars and gas laced with dust. Such striking arms are a hallmark of so-called grand-design spiral galaxies. In M51, also known as the Whirlpool galaxy, these arms serve an important purpose: they are star-formation factories, compressing hydrogen gas and creating clusters of new stars. Some astronomers think that the Whirlpool’s arms are particularly prominent because of the effects of a close encounter with NGC 5195, the small, yellowish galaxy at the outermost tip of one of the arms. The compact galaxy appears to be tugging on the arm, the tidal forces from which trigger new star formation. Hubble’s clear view shows that NGC 5195 is passing behind M51. The small galaxy has been gliding past the Whirlpool for hundreds of millions of years.
Facts about M51 by Keith Turnecliff
The Whirlpool Galaxy has an apparent magnitude of 8.4 and lies at an approximate distance of 23 million light years from Earth. It has the designation NGC 5194 in the New General Catalogue.
In good conditions, the Whirlpool Galaxy can be seen in binoculars. It is quite bright and appears face-on, which makes it a popular target among amateur astronomers and astrophotographers. M51 is also the brightest example of an interacting spiral galaxy in the sky. The best time of year to observe M51 is in the months of March, April and May.