Whirlpool Galaxy

The Whirlpool Galaxy is a familiar one to stargazers and among the many close galaxy neighbors to our own Milky Way. Because of its shape, it was the first galaxy to be classified as a spiral by astronomers. Today, it interests astronomers due to its spiral structure and the interaction it appears to be having with its near neighbor, M51b.

Whirlpool Galaxy Profile

Designation: M51a or NGC 5194
Type: Spiral
Diameter: 60,000 ly
Distance: 23 Mly
Mass: 160 billion M☉
Constellation: Canes Venatici
Facts about the Whirlpool Galaxy

The Whirlpool Galaxy was first discovered in 1773 by Charles Messier, who was charting the skies looking for objects that might be confused with comets.
In 1845, astronomer William Parsons observed the galaxy pair with his telescope at Birr Castle, Ireland, and found the spiral structure of the Whirlpool.
The Whirlpool and its companion, M51b have already passed by or through each other once as they dance through a cosmic merger. The smaller galaxy has been severely disrupted by the encounter, and the Whirlpool’s spiral arms are distorted.
The Whirlpool Galaxy is undergoing huge bursts of starbirth due to its ongoing encounter with its smaller companion galaxy.
The whirlpool, like many other galaxies, has a supermassive black hole at its heart, surrounded by rings of dust. The core of the galaxy is quite quite active — making the Whirlpool what astronomers call a “Seyfert galaxy”.
The Whirlpool’s companion, called M51b, is a dwarf galaxy. Because it is being torn apart by the ongoing interaction, it cannot be easily classified. Its current appearance makes it look like an irregular galaxy.
A bridge of gas and dust ties the two galaxies together as they merge.